Calculation of the radiative properties of photosynthetic microorganisms
Dauchet, Jérémi; Blanco, Stéphane; Cornet, Jean-François; Fournier, Richard
2015-08-01
A generic methodological chain for the predictive calculation of the light-scattering and absorption properties of photosynthetic microorganisms within the visible spectrum is presented here. This methodology has been developed in order to provide the radiative properties needed for the analysis of radiative transfer within photobioreactor processes, with a view to enable their optimization for large-scale sustainable production of chemicals for energy and chemistry. It gathers an electromagnetic model of light-particle interaction along with detailed and validated protocols for the determination of input parameters: morphological and structural characteristics of the studied microorganisms as well as their photosynthetic-pigment content. The microorganisms are described as homogeneous equivalent-particles whose shape and size distribution is characterized by image analysis. The imaginary part of their refractive index is obtained thanks to a new and quite extended database of the in vivo absorption spectra of photosynthetic pigments (that is made available to the reader). The real part of the refractive index is then calculated by using the singly subtractive Kramers-Krönig approximation, for which the anchor point is determined with the Bruggeman mixing rule, based on the volume fraction of the microorganism internal-structures and their refractive indices (extracted from a database). Afterwards, the radiative properties are estimated using the Schiff approximation for spheroidal or cylindrical particles, as a first step toward the description of the complexity and diversity of the shapes encountered within the microbial world. Finally, these predictive results are confronted to experimental normal-hemispherical transmittance spectra for validation. This entire procedure is implemented for Rhodospirillum rubrum, Arthrospira platensis and Chlamydomonas reinhardtii, each representative of the main three kinds of photosynthetic microorganisms, i.e. respectively
Near-infrared radiation absorption properties of covellite (CuS using first-principles calculations
Directory of Open Access Journals (Sweden)
Lihua Xiao
2016-08-01
Full Text Available First-principles density functional theory was used to investigate the electronic structure, optical properties and the origin of the near-infrared (NIR absorption of covellite (CuS. The calculated lattice constant and optical properties are found to be in reasonable agreement with experimental and theoretical findings. The electronic structure reveals that the valence and conduction bands of covellite are determined by the Cu 3d and S 3p states. By analyzing its optical properties, we can fully understand the potential of covellite (CuS as a NIR absorbing material. Our results show that covellite (CuS exhibits NIR absorption due to its metal-like plasma oscillation in the NIR range.
Near-infrared radiation absorption properties of covellite (CuS) using first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Xiao, Lihua, E-mail: xiaolihua@git.edu.cn [School of Materials and Metallurgical Engineering, Guizhou Institute of Technology, Guiyang 550003 (China); College of Physics and Information Science, Hunan Normal University, Changsha 410081 (China); Guizhou Special Functional Materials 2011 Collaborative Innovation Center, Guizhou Institute of Technology, Guiyang 550003 (China); Wu, Jianming; Liu, Yike; Lu, Fanghai [School of Materials and Metallurgical Engineering, Guizhou Institute of Technology, Guiyang 550003 (China); Guizhou Special Functional Materials 2011 Collaborative Innovation Center, Guizhou Institute of Technology, Guiyang 550003 (China); Ran, Jingyu; Qiu, Wei; Shao, Fang [Guizhou Special Functional Materials 2011 Collaborative Innovation Center, Guizhou Institute of Technology, Guiyang 550003 (China); Tang, Dongsheng, E-mail: dstang@hunnu.edu.cn [College of Physics and Information Science, Hunan Normal University, Changsha 410081 (China); Peng, Ping [School of Materials Science and Engineering, Hunan University, Changsha, Hunan 410082 (China)
2016-08-15
First-principles density functional theory was used to investigate the electronic structure, optical properties and the origin of the near-infrared (NIR) absorption of covellite (CuS). The calculated lattice constant and optical properties are found to be in reasonable agreement with experimental and theoretical findings. The electronic structure reveals that the valence and conduction bands of covellite are determined by the Cu 3d and S 3p states. By analyzing its optical properties, we can fully understand the potential of covellite (CuS) as a NIR absorbing material. Our results show that covellite (CuS) exhibits NIR absorption due to its metal-like plasma oscillation in the NIR range.
Properties of undulator radiation
Energy Technology Data Exchange (ETDEWEB)
Veal, B.W.
1985-11-01
Properties of the radiation emitted by a plane sinusoidal undulator are calculated in the far field approximation. Software has been developed to calculate the spectral distribution and polarization of the radiated intensity I(E) at a point on (or integrated over) a cross sectional observation plane of the photon beam. Spatial distribution of monochromatic radiation and power density contours are also calculated. Spectral broadening caused by an electron beam of finite spatial distribution is considered. Dispersive properties of the photon beam, including the dependence on deflection parameter, are analyzed. It is shown that reasonably constant intensity distribution I(E) can be obtained by properly shaping the beam acceptance aperture. 5 refs., 11 figs.
Engineering calculations in radiative heat transfer
Gray, W A; Hopkins, D W
1974-01-01
Engineering Calculations in Radiative Heat Transfer is a six-chapter book that first explains the basic principles of thermal radiation and direct radiative transfer. Total exchange of radiation within an enclosure containing an absorbing or non-absorbing medium is then described. Subsequent chapters detail the radiative heat transfer applications and measurement of radiation and temperature.
Sensitivity of aerosol radiative forcing calculations to spectral resolution
Energy Technology Data Exchange (ETDEWEB)
Grant, K.E.
1996-10-01
Potential impacts of aerosol radiative forcing on climate have generated considerable recent interest. An important consideration in estimating the forcing from various aerosol components is the spectral resolution used for the solar radiative transfer calculations. This paper examines the spectral resolution required from the viewpoint of overlapping spectrally varying aerosol properties with other cross sections. A diagnostic is developed for comparing different band choices, and the impact of these choices on the radiative forcing calculated for typical sulfate and biomass aerosols was investigated.
Radiative properties of dense nanofluids.
Wei, Wei; Fedorov, Andrei G; Luo, Zhongyang; Ni, Mingjiang
2012-09-01
The radiative properties of dense nanofluids are investigated. For nanofluids, scattering and absorbing of electromagnetic waves by nanoparticles, as well as light absorption by the matrix/fluid in which the nanoparticles are suspended, should be considered. We compare five models for predicting apparent radiative properties of nanoparticulate media and evaluate their applicability. Using spectral absorption and scattering coefficients predicted by different models, we compute the apparent transmittance of a nanofluid layer, including multiple reflecting interfaces bounding the layer, and compare the model predictions with experimental results from the literature. Finally, we propose a new method to calculate the spectral radiative properties of dense nanofluids that shows quantitatively good agreement with the experimental results.
A Methodology for Calculating Radiation Signatures
Energy Technology Data Exchange (ETDEWEB)
Klasky, Marc Louis [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wilcox, Trevor [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bathke, Charles G. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); James, Michael R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-05-01
A rigorous formalism is presented for calculating radiation signatures from both Special Nuclear Material (SNM) as well as radiological sources. The use of MCNP6 in conjunction with CINDER/ORIGEN is described to allow for the determination of both neutron and photon leakages from objects of interest. In addition, a description of the use of MCNP6 to properly model the background neutron and photon sources is also presented. Examinations of the physics issues encountered in the modeling are investigated so as to allow for guidance in the user discerning the relevant physics to incorporate into general radiation signature calculations. Furthermore, examples are provided to assist in delineating the pertinent physics that must be accounted for. Finally, examples of detector modeling utilizing MCNP are provided along with a discussion on the generation of Receiver Operating Curves, which are the suggested means by which to determine detectability radiation signatures emanating from objects.
Lagrange interpolation for the radiation shielding calculation
Isozumi, Y; Miyatake, H; Kato, T; Tosaki, M
2002-01-01
Basing on some formulas of Lagrange interpolation derived in this paper, a computer program for table calculations has been prepared. Main features of the program are as follows; 1) maximum degree of polynomial in Lagrange interpolation is 10, 2) tables with both one variable and two variables can be applied, 3) logarithmic transformations of function and/or variable values can be included and 4) tables with discontinuities and cusps can be applied. The program has been carefully tested by using the data tables in the manual of shielding calculation for radiation facilities. For all available tables in the manual, calculations with the program have been reasonably performed under conditions of 1) logarithmic transformation of both function and variable values and 2) degree 4 or 5 of the polynomial.
Calculation of Radiation Damage in SLAC Targets
Energy Technology Data Exchange (ETDEWEB)
Wirth, B D; Monasterio, P; Stein, W
2008-04-03
Ti-6Al-4V alloys are being considered as a positron producing target in the Next Linear Collider, with an incident photon beam and operating temperatures between room temperature and 300 C. Calculations of displacement damage in Ti-6Al-4V alloys have been performed by combining high-energy particle FLUKA simulations with SPECTER calculations of the displacement cross section from the resulting energy-dependent neutron flux plus the displacements calculated from the Lindhard model from the resulting energy-dependent ion flux. The radiation damage calculations have investigated two cases, namely the damage produced in a Ti-6Al-4V SLAC positron target where the irradiation source is a photon beam with energies between 5 and 11 MeV. As well, the radiation damage dose in displacements per atom, dpa, has been calculated for a mono-energetic 196 MeV proton irradiation experiment performed at Brookhaven National Laboratory (BLIP experiment). The calculated damage rate is 0.8 dpa/year for the Ti-6Al-4V SLAC photon irradiation target, and a total damage exposure of 0.06 dpa in the BLIP irradiation experiment. In both cases, the displacements are predominantly ({approx}80%) produced by recoiling ions (atomic nuclei) from photo-nuclear collisions or proton-nuclear collisions, respectively. Approximately 25% of the displacement damage results from the neutrons in both cases. Irradiation effects studies in titanium alloys have shown substantial increases in the yield and ultimate strength of up to 500 MPa and a corresponding decrease in uniform ductility for neutron and high energy proton irradiation at temperatures between 40 and 300 C. Although the data is limited, there is an indication that the strength increases will saturate by doses on the order of a few dpa. Microstructural investigations indicate that the dominant features responsible for the strength increases were dense precipitation of a {beta} (body-centered cubic) phase precipitate along with a high number density
Agriculture-related radiation dose calculations
Energy Technology Data Exchange (ETDEWEB)
Furr, J.M.; Mayberry, J.J.; Waite, D.A.
1987-10-01
Estimates of radiation dose to the public must be made at each stage in the identification and qualification process leading to siting a high-level nuclear waste repository. Specifically considering the ingestion pathway, this paper examines questions of reliability and adequacy of dose calculations in relation to five stages of data availability (geologic province, region, area, location, and mass balance) and three methods of calculation (population, population/food production, and food production driven). Calculations were done using the model PABLM with data for the Permian and Palo Duro Basins and the Deaf Smith County area. Extra effort expended in gathering agricultural data at succeeding environmental characterization levels does not appear justified, since dose estimates do not differ greatly; that effort would be better spent determining usage of food types that contribute most to the total dose; and that consumption rate and the air dispersion factor are critical to assessment of radiation dose via the ingestion pathway. 17 refs., 9 figs., 32 tabs.
Program calculation of thermodynamic properties
Gill, Walter; Filho, Fernando Fachini; Ribeirodeoliveira, Ronaldo
1986-12-01
The determination of the thermodynamic properties are examined through the basic equations such as: state equation (Beattie-Bridgeman Form), saturation pressure equation, specific heat constant pressure or constant volume equation, and specific volume or density of liquid equation.
Energy Technology Data Exchange (ETDEWEB)
NONE
2003-07-01
These scientific days had for objective to draw up the situation of calculation codes of radiation transport, of sources estimation, of radiation doses managements and to draw the future perspectives. (N.C.)
Monte-Carlo Calculation of Radiation Shield
Institute of Scientific and Technical Information of China (English)
2008-01-01
<正>The electron accelerator is used in the industry and society more and more. It produces electron beam with high radiation dose and lots of X rays when the electron beam interact with material. Because the X
Approximate design calculation methods for radiation streaming in shield irregularities
Energy Technology Data Exchange (ETDEWEB)
Miura, Toshimasa; Hirao, Yoshihiro [Ship Research Inst., Mitaka, Tokyo (Japan); Yoritsune, Tsutomu
1997-10-01
Investigation and assessment are made for approximate design calculation methods of radiation streaming in shield irregularities. Investigation is made for (1) source, (2) definition of streaming radiation components, (3) calculation methods of streaming radiation, (4) streaming formulas for each irregularity, (5) difficulties in application of streaming formulas, etc. Furthermore, investigation is made for simple calculation codes and albedo data. As a result, it is clarified that streaming calculation formulas are not enough to cover various irregularities and their accuracy or application limit is not sufficiently clear. Accurate treatment is not made in the formulas with respect to the radiation behavior for slant incidence, bend part, offset etc., that results in too much safety factors in the design calculation and distrust of the streaming calculation. To overcome the state and improve the accuracy of the design calculation for shield irregularities, it is emphasized to assess existing formulas and develop better formulas based on systematic experimental studies. (author)
Calculation of patterns of solar radiation within urban geometries
Carrasco Hernandez, Roberto
2015-01-01
ABSTRACTThe University of ManchesterRoberto Carrasco-Hernandez. PhD in Earth Atmospheric and Environmental Sciences.Calculation of patterns of solar radiation within urban geometries.30 May 2015The present work proposes methods to calculate street-level exposures to solar radiation. The methods comprise a combination of different software algorithms, online databases and real-time standard measurements of solar radiation. Firstly, the use of the free access image database “Google Street View”...
LDRD Final Review: Radiation Transport Calculations
Energy Technology Data Exchange (ETDEWEB)
Goorley, John Timothy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Morgan, George Lake [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lestone, John Paul [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-06-22
Both high-fidelity & toy simulations are being used to understand measured signals and improve the Area 11 NDSE diagnostic. We continue to gain more and more confidence in the ability for MCNP to simulate neutron and photon transport from source to radiation detector.
Methods of calculating radiation absorbed dose.
Wegst, A V
1987-01-01
The new tumoricidal radioactive agents being developed will require a careful estimate of radiation absorbed tumor and critical organ dose for each patient. Clinical methods will need to be developed using standard imaging or counting instruments to determine cumulated organ activities with tracer amounts before the therapeutic administration of the material. Standard MIRD dosimetry methods can then be applied.
Radiative properties of ice clouds
Energy Technology Data Exchange (ETDEWEB)
Mitchell, D.L.; Koracin, D.; Carter, E. [Desert Research Institute, Reno, NV (United States)
1996-04-01
A new treatment of cirrus cloud radiative properties has been developed, based on anomalous diffraction theory (ADT), which does not parameterize size distributions in terms of an effective radius. Rather, is uses the size distribution parameters directly, and explicitly considers the ice particle shapes. There are three fundamental features which characterize this treatment: (1) the ice path radiation experiences as it travels through an ice crystal is parameterized, (2) only determines the amount of radiation scattered and absorbed, and (3) as in other treatments, the projected area of the size distribution is conserved. The first two features are unique to this treatment, since it does not convert the ice particles into equivalent volume or area spheres in order to apply Mie theory.
Calculation of tin atomic data and plasma properties.
Energy Technology Data Exchange (ETDEWEB)
Morozov, V.; Tolkach, V.; Hassanein, A.
2005-08-26
This report reviews the major methods and techniques we use in generating basic atomic and plasma properties relevant to extreme ultraviolet (EUV) lithography applications. The basis of the work is the calculation of the atomic energy levels, transitions probabilities, and other atomic data by various methods, which differ in accuracy, completeness, and complication. Later on, we calculate the populations of atomic levels and ion states in plasmas by means of the collision-radiation equilibrium (CRE) model. The results of the CRE model are used as input to the thermodynamic functions, such as pressure and temperature from the internal energy and density (equation of state), electric resistance, thermal conduction, and other plasma properties. In addition, optical coefficients, such as emission and absorption coefficients, are generated to resolve a radiation transport equation (RTE). The capabilities of our approach are demonstrated by generating the required atomic and plasma properties for tin ions and plasma within the EUV region near 13.5 nm.
Physical and radiative properties of the first core accretion shock
Commerçon, Benoît; Chabrier, Gilles; Chièze, Jean-Pierre
2011-01-01
Radiative shocks play a dominant role in star formation. The accretion shocks on the first and second Larson's cores involve radiative processes and are thus characteristic of radiative shocks. In this study, we explore the formation of the first Larson's core and characterize the radiative and dynamical properties of the accretion shock, using both analytical and numerical approaches. We develop both numerical RHD calculations and a semi-analytical model that characterize radiative shocks in various physical conditions, for radiating or barotropic fluids. Then, we perform 1D spherical collapse calculations of the first Larson's core, using a grey approximation for the opacity of the material. We consider three different models for radiative transfer, namely: the barotropic approximation, the FLD approximation and the more complete M1 model. We investigate the characteristic properties of the collapse and of the first core formation. Comparison between the numerical results and our semi-analytical model shows...
Effective UV radiation from model calculations and measurements
Feister, Uwe; Grewe, Rolf
1994-01-01
Model calculations have been made to simulate the effect of atmospheric ozone and geographical as well as meteorological parameters on solar UV radiation reaching the ground. Total ozone values as measured by Dobson spectrophotometer and Brewer spectrometer as well as turbidity were used as input to the model calculation. The performance of the model was tested by spectroradiometric measurements of solar global UV radiation at Potsdam. There are small differences that can be explained by the uncertainty of the measurements, by the uncertainty of input data to the model and by the uncertainty of the radiative transfer algorithms of the model itself. Some effects of solar radiation to the biosphere and to air chemistry are discussed. Model calculations and spectroradiometric measurements can be used to study variations of the effective radiation in space in space time. The comparability of action spectra and their uncertainties are also addressed.
Nomograms for calculation of defence from braking radiation
Bespalov, V I; Shtejn, M M
2002-01-01
More precise nomograms for calculation of thickness of shielding against direct Bremsstrahlung are obtained with taking account of recently introduced radiation safety standards and disadvantages of earlier used simplified nomograms. The nomograms are built for three shielding materials (lead, iron, concrete) for 16 angular of radiation exit in the range of 0-180 deg and 22 values of electron energy within the interval of 0.5-15 MeV. A special computer program, is developed to calculate the radiation protection parameters using a great set of nomograms proposed
Calculation of the dose caused by internal radiation
Energy Technology Data Exchange (ETDEWEB)
NONE
2000-07-01
For the purposes of monitoring radiation exposure it is necessary to determine or to estimate the dose caused by both external and internal radiation. When comparing the value of exposure to the dose limits, account must be taken of the total dose incurred from different sources. This guide explains how to calculate the committed effective dose caused by internal radiation and gives the conversion factors required for the calculation. Application of the maximum values for radiation exposure is dealt with in ST guide 7.2, which also sets out the definitions of the quantities and concepts most commonly used in the monitoring of radiation exposure. The monitoring of exposure and recording of doses are dealt with in ST Guides 7.1 and 7.4.
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...
Comparison of the performance of net radiation calculation models
DEFF Research Database (Denmark)
Kjærsgaard, Jeppe Hvelplund; Cuenca, R H; Martinez-Cob, A
2009-01-01
values of net radiation were calculated using three net outgoing long-wave radiation models and compared to measured values. Four meteorological datasets representing two climate regimes, a sub-humid, high-latitude environment and a semi-arid mid-latitude environment, were used to test the models...... meteorological input data is limited. Model predictions were found to have a higher bias and scatter when using summed calculated hourly time steps compared to using daily input data.......Daily values of net radiation are used in many applications of crop-growth modeling and agricultural water management. Measurements of net radiation are not part of the routine measurement program at many weather stations and are commonly estimated based on other meteorological parameters. Daily...
Prenatal radiation exposure. Dose calculation; Praenatale Strahlenexposition. Dosisermittlung
Energy Technology Data Exchange (ETDEWEB)
Scharwaechter, C.; Schwartz, C.A.; Haage, P. [University Hospital Witten/Herdecke, Wuppertal (Germany). Dept. of Diagnostic and Interventional Radiology; Roeser, A. [University Hospital Witten/Herdecke, Wuppertal (Germany). Dept. of Radiotherapy and Radio-Oncology
2015-05-15
The unborn child requires special protection. In this context, the indication for an X-ray examination is to be checked critically. If thereupon radiation of the lower abdomen including the uterus cannot be avoided, the examination should be postponed until the end of pregnancy or alternative examination techniques should be considered. Under certain circumstances, either accidental or in unavoidable cases after a thorough risk assessment, radiation exposure of the unborn may take place. In some of these cases an expert radiation hygiene consultation may be required. This consultation should comprise the expected risks for the unborn while not perturbing the mother or the involved medical staff. For the risk assessment in case of an in-utero X-ray exposition deterministic damages with a defined threshold dose are distinguished from stochastic damages without a definable threshold dose. The occurrence of deterministic damages depends on the dose and the developmental stage of the unborn at the time of radiation. To calculate the risks of an in-utero radiation exposure a three-stage concept is commonly applied. Depending on the amount of radiation, the radiation dose is either estimated, roughly calculated using standard tables or, in critical cases, accurately calculated based on the individual event. The complexity of the calculation thereby increases from stage to stage. An estimation based on stage one is easily feasible whereas calculations based on stages two and especially three are more complex and often necessitate execution by specialists. This article demonstrates in detail the risks for the unborn child pertaining to its developmental phase and explains the three-stage concept as an evaluation scheme. It should be noted, that all risk estimations are subject to considerable uncertainties.
Calculation of the characteristics of infrared synchrotron radiation
Maslova, M V; Maltsev, M A
2005-01-01
Subroutines for calculating the spectral and angular characteristics of infrared synchrotron radiation are developed. Corresponding calculations are carried out for a number of proton and electron accelerators. The results obtained enable methods to be developed for beam diagnostics as well as highly sensitive detectors of infrared radiation for remote contactless nondestructive diagnostics and for investigating bunches and high-speed processes in ring-type (CERN /SEPS-LHC) and linear (GSI bunch target) accelerators, and also the thermal fields in nuclear power plants.
Scaling algorithms for the calculation of solar radiative fluxes
Energy Technology Data Exchange (ETDEWEB)
Suzuki, Tsuneaki [Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 236-0001 (Japan)], E-mail: tsuneaki@jamstec.go.jp; Nakajima, Teruyuki [Center for Climate System Research, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8568 (Japan); Tanaka, Masayuki [Department of Environmental Information Engineering, Tohoku Institute of Technology, 35-1 Kasumi-cho, Yagiyama, Taihaku-ku, Sendai, Miyagi 982-8577 (Japan)
2007-10-15
We derived new scaling formulae based on the method of successive orders of scattering to calculate solar radiative flux. In this report, we demonstrate a multiple scaling method, in which we introduce scaling factors for each scattering order independently. The formula of radiative transfer by the method of successive orders of scattering cannot be solved rapidly except in the case of optically thin atmospheres. Then we further derived a double scaling method, which scales the ordinary radiative transfer equation by two scaling factors. We applied the double scaling method to two-stream and four-stream approximations of the discrete ordinates method. Comparing the results of the double scaling method with those of the delta-M method, we found that the double scaling method improved the accuracy of radiative fluxes at large solar zenith angles, especially in the optically thin region, and that in the region where multiple scattering dominates, its accuracy was comparable to that of the delta-M method. Once we determined the scaling factors appropriately, the double scaling method calculated radiative fluxes as rapidly as the delta-M method in the two-stream and four-stream approximations. This method, therefore, is useful for accurate computation of solar radiative fluxes in general circulation models.
Neutron dosimetry and radiation damage calculations for HFBR
Energy Technology Data Exchange (ETDEWEB)
Greenwood, L.R.; Ratner, R.T. [Pacific Northwest National Lab., TN (United States)
1998-03-01
Neutron dosimetry measurements have been conducted for various positions of the High Flux Beam Reactor (HFBR) at Brookhaven National Laboratory (BNL) in order to measure the neutron flux and energy spectra. Neutron dosimetry results and radiation damage calculations are presented for positions V10, V14, and V15.
Solar radiation calculation methodology for building exterior surfaces
Energy Technology Data Exchange (ETDEWEB)
De la Flor, Francisco Jose Sanchez; Ortiz Cebolla, Rafael; Luis Molina Felix, Jose; Alvarez Dominguez, Servando [E S. Ingenieros. Grupo de Termotecnia, Avda. de los descubrimientos, s/n 41092 Sevilla (Spain)
2005-11-01
The present article shows a new methodology of calculation of the direct, diffuse and reflected incident solar radiation, in all type of surfaces, either in open urban environments or inside buildings. This methodology is applicable in problems related to solar access (space heating in buildings, shadowing of open spaces), solar gains (space cooling in buildings), and daylighting. Solar radiation is the most important contribution to the surface and volumetric energy balance during the daytime. Particularly, solar radiation is the main contributor to heat gains in buildings, especially in residential buildings, where internal gains are very low. Utilization of daylight in buildings may result in significant savings in electricity consumption for lighting while creating a higher quality indoor environment. Additional energy savings may also be realized during cooling season, when reduction of internal heat gains due to electric lighting results in a corresponding reduction of cooling energy consumption. The analysis of the existing calculation methods and proposed in the scientific bibliography for the calculation of the solar radiation in problems of solar access in winter, solar gains in summer, and daylighting, takes us to the necessity of outlining a new and complete methodology. This new methodology is applicable to all these problems with a great accuracy and calculation speed. (author)
The calculation of features of X-ray radiation
Directory of Open Access Journals (Sweden)
Dushkin S. A.
2008-12-01
Full Text Available On the basis of theoretical research an algorithm was received, allowing to calculate the features of X-ray radiation: spectral resolution, mean photon energy, homogeneity coefficient, the first and the second half-value layer by means of building a spectrum of bremsstrahlung X-ray radiation and determining the mean photon energy disregarding and taking into account the filter, required for the determination of 1st HVL; an analysis and comparison of calculated features of standard X-ray radiations of series L, N, W and H with similar features, provided in DSTU ISO 4037-1:2006 were carried out; the criterion of applicability of the given algorithm – the homogeneity coefficient value – was determined on the basis of the analysis and comparison.
Numeric spectral radiation hydrodynamic calculations of supernova shock breakouts
Sapir, Nir
2014-01-01
We present here an efficient numerical scheme for solving the non-relativistic 1D radiation-hydrodynamics equations including inelastic Compton scattering, which is not included in most codes and is crucial for solving problems such as shock breakout. The devised code is applied to the problems of a steady-state planar radiation mediated shock (RMS) and RMS breakout from a stellar envelope. The results are in agreement with those of a previous work on shock breakout \\citep{Sapir13}, in which Compton equilibrium between matter and radiation was assumed and the "effective photon" approximation was used to describe the radiation spectrum. In particular, we show that the luminosity and its temporal dependence, the peak temperature at breakout, and the universal shape of the spectral fluence derived in this earlier work are all accurate. Although there is a discrepancy between the spectral calculations and the effective photon approximation due to the inaccuracy of the effective photon approximation estimate of th...
Radiative torques: Analytical Model and Basic Properties
Lazarian, Alex
2007-01-01
We attempt to get a physical insight into grain alignment processes by studying basic properties of radiative torques (RATs). For this purpose we consider a simple toy model of a helical grain that reproduces well the basic features of RATs. The model grain consists of a spheroidal body with a mirror attached at an angle to it. Being very simple, the model allows analytical description of RATs that act upon it. We show a good correspondence of RATs obtained for this model and those of irregular grains calculated by DDSCAT. Our analysis of the role of different torque components for grain alignment reveals that one of the three RAT components does not affect the alignment, but induces only for grain precession. The other two components provide a generic alignment with grain long axes perpendicular to the radiation direction, if the radiation dominates the grain precession, and perpendicular to magnetic field, otherwise. We study a self-similar scaling of RATs as a function of $\\lambda/a_{eff}$. We show that th...
Impact of dose calculation algorithm on radiation therapy
Institute of Scientific and Technical Information of China (English)
Wen-Zhou; Chen; Ying; Xiao; Jun; Li
2014-01-01
The quality of radiation therapy depends on the ability to maximize the tumor control probability while minimizing the normal tissue complication probability.Both of these two quantities are directly related to the accuracy of dose distributions calculated by treatment planning systems.The commonly used dose calculation algorithms in the treatment planning systems are reviewed in this work.The accuracy comparisons among these algorithms are illustrated by summarizing the highly cited research papers on this topic.Further,the correlation between the algorithms and tumor control probability/normal tissue complication probability values are manifested by several recent studies from different groups.All the cases demonstrate that dose calculation algorithms play a vital role in radiation therapy.
Calculated Bulk Properties of the Actinide Metals
DEFF Research Database (Denmark)
Skriver, Hans Lomholt; Andersen, O. K.; Johansson, B.
1978-01-01
Self-consistent relativistic calculations of the electronic properties for seven actinides (Ac-Am) have been performed using the linear muffin-tin orbitals method within the atomic-sphere approximation. Exchange and correlation were included in the local spin-density scheme. The theory explains...... the variation of the atomic volume and the bulk modulus through the 5f series in terms of an increasing 5f binding up to plutonium followed by a sudden localisation (through complete spin polarisation) in americium...
Calculated Bulk Properties of the Actinide Metals
DEFF Research Database (Denmark)
Skriver, Hans Lomholt; Andersen, O. K.; Johansson, B.
1978-01-01
Self-consistent relativistic calculations of the electronic properties for seven actinides (Ac-Am) have been performed using the linear muffin-tin orbitals method within the atomic-sphere approximation. Exchange and correlation were included in the local spin-density scheme. The theory explains t...... the variation of the atomic volume and the bulk modulus through the 5f series in terms of an increasing 5f binding up to plutonium followed by a sudden localisation (through complete spin polarisation) in americium...
Efficient vector radiative transfer calculations in vertically inhomogeneous cloudy atmospheres
van Diedenhoven, Bastiaan; Hasekamp, Otto P.; Landgraf, Jochen
2006-08-01
Accurate radiative transfer calculations in cloudy atmospheres are generally time consuming, limiting their practical use in satellite remote sensing applications. We present a model to efficiently calculate the radiative transfer of polarized light in atmospheres that contain homogeneous cloud layers. This model combines the Gauss-Seidel method, which is efficient for inhomogeneous cloudless atmospheres, with the doubling method, which is efficient for homogeneous cloud layers. Additionally to reduce the computational effort for radiative transfer calculations in absorption bands, the cloud reflection and transmission matrices are interpolated over the absorption and scattering optical thicknesses within the cloud layer. We demonstrate that the proposed radiative transfer model in combination with this interpolation technique is efficient for the simulation of satellite measurements for inhomogeneous atmospheres containing one homogeneous cloud layer. For example, the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) measurements in the oxygen A band (758-773 nm) and the Hartley-Huggins ozone band (295-335 nm) with a spectral resolution of 0.4 nm can be simulated for these atmospheres within 1 min on a 2.8 GHz PC with an accuracy better than 0.1%.
Rabacus: A Python Package for Analytic Cosmological Radiative Transfer Calculations
Altay, Gabriel
2015-01-01
We describe Rabacus, a Python package for calculating the transfer of hydrogen ionizing radiation in simplified geometries relevant to astronomy and cosmology. We present example solutions for three specific cases: 1) a semi-infinite slab gas distribution in a homogeneous isotropic background, 2) a spherically symmetric gas distribution with a point source at the center, and 3) a spherically symmetric gas distribution in a homogeneous isotropic background. All problems can accommodate arbitrary spectra and density profiles as input. The solutions include a treatment of both hydrogen and helium, a self-consistent calculation of equilibrium temperatures, and the transfer of recombination radiation. The core routines are written in Fortran 90 and then wrapped in Python leading to execution speeds thousands of times faster than equivalent routines written in pure Python. In addition, all variables have associated units for ease of analysis. The software is part of the Python Package Index and the source code is a...
Radiation Shielding Properties of Some Marbles in Turkey
Günoǧlu, K.; Akkurt, I.
2011-12-01
Especially after development of technology, radiation started to be used in a large fields such as medicine, industry and energy. Using radiation in those fields bring hazordous effect of radition into humancell. Thus radiation protection becomes important in physics. Although there are three ways for radiation protection, shielding of the radiation is the most commonly used method. Natural Stones such as marble is used as construction material especially in critical building and thus its radiation shielding capability should be determined. In this study, gamma ray shielding properties of some different types of marble mined in Turkey, have been measured using a NaI(Tl) scintillator detector. The measured results were also compared with the theoretical calculations XCOM.
THE IMPACT OF RELATIVE HUMIDITY ON THE RADIATIVE PROPERTY AND RADIATIVE FORCING OF SULFATE AEROSOL
Institute of Scientific and Technical Information of China (English)
张立盛; 石广玉
2001-01-01
With the data of complex refractive index of sulfate aerosol, the radiative properties of the aerosol under 8 relative humidity conditions are calculated in this paper. By using the concentration distribution from two CTM models and LASG GOALS/AGCM, the radiative forcing due to hygroscopic sulfate aerosol is simulated. The results show that: (1) With the increase of relative humidity, the mass extinction coefficiency factor decreases in the shortwave spectrum: single scattering albedo keeps unchanged except for a little increase in longwave spectrum, and asymmetry factor increases in whole spectrum. (2) Larger differences occur in radiative forcing simulated by using two CTM data, and the global mean forcing is -0. 268 and -0. 816 W/m2,respectively. (3) When the impact of relative humidity on radiative property is taken into account,the distribution pattern of radiative forcing due to the wet particles is very similar to that of dry sulfate, but the forcing value decreases by 6%.
Studying laser radiation effect on steel structure and properties
Directory of Open Access Journals (Sweden)
А. М. Gazaliyev
2016-07-01
Full Text Available There was studied the effect of laser radiation on the structure and properties of annealed and tempered steel with different content of carbon. For surface hardening there was used a laser complex equipped with Nd: YAG pulse laser with power density up to 30 kW/сm2. As a result of the carried-out studies there were calculated characteristics of laser, steel microstructure and properties.
Calculation of Solar Radiation by Using Regression Methods
Kızıltan, Ö.; Şahin, M.
2016-04-01
In this study, solar radiation was estimated at 53 location over Turkey with varying climatic conditions using the Linear, Ridge, Lasso, Smoother, Partial least, KNN and Gaussian process regression methods. The data of 2002 and 2003 years were used to obtain regression coefficients of relevant methods. The coefficients were obtained based on the input parameters. Input parameters were month, altitude, latitude, longitude and landsurface temperature (LST).The values for LST were obtained from the data of the National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR) satellite. Solar radiation was calculated using obtained coefficients in regression methods for 2004 year. The results were compared statistically. The most successful method was Gaussian process regression method. The most unsuccessful method was lasso regression method. While means bias error (MBE) value of Gaussian process regression method was 0,274 MJ/m2, root mean square error (RMSE) value of method was calculated as 2,260 MJ/m2. The correlation coefficient of related method was calculated as 0,941. Statistical results are consistent with the literature. Used the Gaussian process regression method is recommended for other studies.
Radiation damage/activity calculation for CSNS target station
Yin, W.; Liang, T. J.; Yu, Q. Z.; Jia, X. J.
2010-03-01
The radiation damages have been performed for Chinese spallation neutron source (CSNS) target center components that relies on Monte Carlo simulation code MCNPX. During the calculation, Bertini intranuclear cascade model, three level-density formulation GCCI, and multistage pre-equilibrium model MPM on which are provided within MCNPX are employed. We calculate the displacement per atom (DPA) and afterheat of the tungsten target, the stainless steel target vessel window and the aluminum alloy moderator vessel. As a hundred kW-level source, these spallation center components have the lifetime more than 5 year. We also give the activity for the T0 chopper of the beam line HIPD to get the primary data for making out a maintenance scenario.
Energy Technology Data Exchange (ETDEWEB)
Gabriel, P. [Colorado State Univ., Fort Collins, CO (United States)
1995-09-01
The use of cloud fraction as a means of incorporating horizontal cloud inhomogeneity in radiative transfer calculations is widespread in the atmospheric science community. This research attempts to bypass the use of cloud fraction in radiative transfer modeling for two-dimensional media. Gabriel describes two approximation techniques useful in calculating the domain averaged bulk radiative properties such as albedo, flux divergence and mean radiance that dispense with the need to use cloud fraction as a specifier of cloud inhomogeneity. The results suggest that the variability of the medium can largely be accounted for through the pseudo-source term, offering hope of parameterizing the equation of transfer in terms of the statistical properties of the medium. 1 fig.
Fisenko, Anatoliy I
2014-01-01
Using polylogarithm functions the exact analytical expressions for the radiative and thermodynamic properties of blackbody radiation, such as the Wien displacement law, Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, and pressure in the finite range of frequencies are constructed. The obtained expressions allow us to tabulate these functions in various finite frequency bands at different temperatures for practical applications. As an example, the radiative and thermodynamic functions using experimental data for the monopole spectrum of the Cosmic Microwave Background (CMB) radiation measured by the COBE FIRAS instrument in the 60 - 600 GHz frequency interval at the temperature T = 2.725 K are calculated. The expressions obtained for the radiative and thermodynamic functions can be easily presented in wavelength and wavenumber domains.
Depletion calculations for the McClellan Nuclear Radiation Center.
Energy Technology Data Exchange (ETDEWEB)
Klann, R. T.; Newell, D. L.
1997-12-08
Depletion calculations have been performed for the McClellan reactor history from January 1990 through August 1996. A database has been generated for continuing use by operations personnel which contains the isotopic inventory for all fuel elements and fuel-followed control rods maintained at McClellan. The calculations are based on the three-dimensional diffusion theory code REBUS-3 which is available through the Radiation Safety Information Computational Center (RSICC). Burnup-dependent cross-sections were developed at zero power temperatures and full power temperatures using the WIMS code (also available through RSICC). WIMS is based on discretized transport theory to calculate the neutron flux as a function of energy and position in a one-dimensional cell. Based on the initial depletion calculations, a method was developed to allow operations personnel to perform depletion calculations and update the database with a minimal amount of effort. Depletion estimates and calculations can be performed by simply entering the core loading configuration, the position of the control rods at the start and end of cycle, the reactor power level, the duration of the reactor cycle, and the time since the last reactor cycle. The depletion and buildup of isotopes of interest (heavy metal isotopes, erbium isotopes, and fission product poisons) are calculated for all fuel elements and fuel-followed control rods in the MNRC inventory. The reactivity loss from burnup and buildup of fission product poisons and the peak xenon buildup after shutdown are also calculated. The reactivity loss from going from cold zero power to hot full power can also be calculated by using the temperature-dependent, burnup-dependent cross-sections. By calculating all of these reactivity effects, operations personnel are able to estimate the total excess reactivity necessary to run the reactor for the given cycle. This method has also been used to estimate the worth of individual control rods. Using this
Fisenko, Anatoliy I.; Lemberg, Vladimir
2014-07-01
Using the explicit form of the functions to describe the monopole and dipole spectra of the Cosmic Microwave Background (CMB) radiation, the exact expressions for the temperature dependences of the radiative and thermodynamic functions, such as the total radiation power per unit area, total energy density, number density of photons, Helmholtz free energy density, entropy density, heat capacity at constant volume, and pressure in the finite range of frequencies v 1≤ v≤ v 2 are obtained. Since the dependence of temperature upon the redshift z is known, the obtained expressions can be simply presented in z representation. Utilizing experimental data for the monopole and dipole spectra measured by the COBE FIRAS instrument in the 60-600 GHz frequency interval at the temperature T=2.72548 K, the values of the radiative and thermodynamic functions, as well as the radiation density constant a and the Stefan-Boltzmann constant σ are calculated. In the case of the dipole spectrum, the constants a and σ, and the radiative and thermodynamic properties of the CMB radiation are obtained using the mean amplitude T amp=3.358 mK. It is shown that the Doppler shift leads to a renormalization of the radiation density constant a, the Stefan-Boltzmann constant σ, and the corresponding constants for the thermodynamic functions. The expressions for new astrophysical parameters, such as the entropy density/Boltzmann constant, and number density of CMB photons are obtained. The radiative and thermodynamic properties of the Cosmic Microwave Background radiation for the monopole and dipole spectra at redshift z≈1089 are calculated.
Energy Technology Data Exchange (ETDEWEB)
NONE
2000-07-01
The guide sets out the mathematical definitions and principles involved in the calculation of the equivalent dose and the effective dose, and the instructions concerning the application of the maximum values of these quantities. further, for monitoring the dose caused by internal radiation, the guide defines the limits derived from annual dose limits (the Annual Limit on Intake and the Derived Air Concentration). Finally, the guide defines the operational quantities to be used in estimating the equivalent dose and the effective dose, and also sets out the definitions of some other quantities and concepts to be used in monitoring radiation exposure. The guide does not include the calculation of patient doses carried out for the purposes of quality assurance.
Thermal Radiative Properties of Xonotlite Insulation Material
Institute of Scientific and Technical Information of China (English)
Xinxin ZHANG; Gaosheng WEI; Fan YU
2005-01-01
This paper presents experimental results of thermal radiative properties of xonotlite-type calcium silicate insulation material. Transmittance spectra were first taken using Fourier transform infrared spectrometer (FTIR)for the samples with ρ = 234 kg/m3. Specific extinction coefficient spectra were then obtained by applying Beer's law.Finally,by using the diffusion approximation,the specific Rossland mean extinction coefficients and radiative thermal conductivities were obtained for various temperatures. The results show that the specific spectral extinction coefficient of xonotlite is larger than 7 m2/kg in the whole measured spectra, and diffusion approximation equation is a reasonable description of radiative heat transfer in xonotlite insulation material. The specific Rossland mean extinction coefficient of xonotlite has a maximum ualue at 400 K and the radiative thermal conductivity is almost proportional to the cube of temperature.
Geant4 calculations for space radiation shielding material Al2O3
Capali, Veli; Acar Yesil, Tolga; Kaya, Gokhan; Kaplan, Abdullah; Yavuz, Mustafa; Tilki, Tahir
2015-07-01
Aluminium Oxide, Al2O3 is the most widely used material in the engineering applications. It is significant aluminium metal, because of its hardness and as a refractory material owing to its high melting point. This material has several engineering applications in diverse fields such as, ballistic armour systems, wear components, electrical and electronic substrates, automotive parts, components for electric industry and aero-engine. As well, it is used as a dosimeter for radiation protection and therapy applications for its optically stimulated luminescence properties. In this study, stopping powers and penetrating distances have been calculated for the alpha, proton, electron and gamma particles in space radiation shielding material Al2O3 for incident energies 1 keV - 1 GeV using GEANT4 calculation code.
Geant4 calculations for space radiation shielding material Al2O3
Directory of Open Access Journals (Sweden)
Capali Veli
2015-01-01
Full Text Available Aluminium Oxide, Al2O3 is the most widely used material in the engineering applications. It is significant aluminium metal, because of its hardness and as a refractory material owing to its high melting point. This material has several engineering applications in diverse fields such as, ballistic armour systems, wear components, electrical and electronic substrates, automotive parts, components for electric industry and aero-engine. As well, it is used as a dosimeter for radiation protection and therapy applications for its optically stimulated luminescence properties. In this study, stopping powers and penetrating distances have been calculated for the alpha, proton, electron and gamma particles in space radiation shielding material Al2O3 for incident energies 1 keV – 1 GeV using GEANT4 calculation code.
Fisenko, Anatoliy I
2015-01-01
The general analytical expressions for the thermal radiative and thermodynamic properties of a real-body are obtained in a finite range of frequencies at different temperatures. The frequency dependence of the spectral emissivity is represented as a power series. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and total emissivity are expressed in terms of the polylogarithm functions. The general expressions for the thermal radiative and thermodynamic functions are applied for the study of thermal radiation of liquid and solid zirconium carbide. These functions are calculated using experimental data for the frequency dependence of the normal spectral emissivity in the visible-near infrared range at the melting (freezing) point. The gaps between the thermal radiative and thermodynamic functions of liquid and solid zirconium carbide are observed. The g...
Numerical calculations of magnetic properties of nanostructures
Kapitan, Vitalii; Nefedev, Konstantin
2015-01-01
Magnetic force microscopy and scanning tunneling microscopy data could be used to test computer numerical models of magnetism. The elaborated numerical model of a face-centered lattice Ising spins is based on pixel distribution in the image of magnetic nanostructures obtained by using scanning microscope. Monte Carlo simulation of the magnetic structure model allowed defining the temperature dependence of magnetization; calculating magnetic hysteresis curves and distribution of magnetization on the surface of submonolayer and monolayer nanofilms of cobalt, depending on the experimental conditions. Our developed package of supercomputer parallel software destined for a numerical simulation of the magnetic-force experiments and allows obtaining the distribution of magnetization in one-dimensional arrays of nanodots and on their basis. There has been determined interpretation of magneto-force microscopy images of magnetic nanodots states. The results of supercomputer simulations and numerical calculations are in...
Cloud radiative properties and aerosol - cloud interaction
Viviana Vladutescu, Daniela; Gross, Barry; Li, Clement; Han, Zaw
2015-04-01
The presented research discusses different techniques for improvement of cloud properties measurements and analysis. The need for these measurements and analysis arises from the high errors noticed in existing methods that are currently used in retrieving cloud properties and implicitly cloud radiative forcing. The properties investigated are cloud fraction (cf) and cloud optical thickness (COT) measured with a suite of collocated remote sensing instruments. The novel approach makes use of a ground based "poor man's camera" to detect cloud and sky radiation in red, green, and blue with a high spatial resolution of 30 mm at 1km. The surface-based high resolution photography provides a new and interesting view of clouds. As the cloud fraction cannot be uniquely defined or measured, it depends on threshold and resolution. However as resolution decreases, cloud fraction tends to increase if the threshold is below the mean, and vice versa. Additionally cloud fractal dimension also depends on threshold. Therefore these findings raise concerns over the ability to characterize clouds by cloud fraction or fractal dimension. Our analysis indicate that Principal Component analysis may lead to a robust means of quantifying cloud contribution to radiance. The cloud images are analyzed in conjunction with a collocated CIMEL sky radiometer, Microwave Radiometer and LIDAR to determine homogeneity and heterogeneity. Additionally, MFRSR measurements are used to determine the cloud radiative properties as a validation tool to the results obtained from the other instruments and methods. The cloud properties to be further studied are aerosol- cloud interaction, cloud particle radii, and vertical homogeneity.
Calculations for Tera-Hertz (THZ) Radiation Sources
Spencer, James
2005-01-01
We explore possibilities for THz sources from 0.3 - 30 THz. While still inaccessible, this broad gap is even wider for advanced acceleration schemes extending from X or, at most, W band RF at the low end up to CO2 lasers. While the physical implementations of these two approaches are quite different, both are proving difficult to develop so that even lower frequency, superconducting RF seems to be the currently preferred means. Similarly, the validity of modelling techniques varies greatly over this range of frequencies but generally mandates coupling Maxwells equations to the appropriate device transport physics for which there are many options. Here we calculate radiation from shaped transmission lines using finite-difference, time-domain (FDTD) simulations of Maxwells equations coupled to Monte-Carlo techniques for both the production and transport physics of short electron pulses. Examples of THz sources that demonstrate coherent interference effects will be discussed with the goal o...
Radiative transfer calculated from a Markov chain formalism
Esposito, L. W.; House, L. L.
1978-01-01
The theory of Markov chains is used to formulate the radiative transport problem in a general way by modeling the successive interactions of a photon as a stochastic process. Under the minimal requirement that the stochastic process is a Markov chain, the determination of the diffuse reflection or transmission from a scattering atmosphere is equivalent to the solution of a system of linear equations. This treatment is mathematically equivalent to, and thus has many of the advantages of, Monte Carlo methods, but can be considerably more rapid than Monte Carlo algorithms for numerical calculations in particular applications. We have verified the speed and accuracy of this formalism for the standard problem of finding the intensity of scattered light from a homogeneous plane-parallel atmosphere with an arbitrary phase function for scattering. Accurate results over a wide range of parameters were obtained with computation times comparable to those of a standard 'doubling' routine. The generality of this formalism thus allows fast, direct solutions to problems that were previously soluble only by Monte Carlo methods. Some comparisons are made with respect to integral equation methods.
A centralized dose calculation system for radiation therapy.
Xiao, Y; Galvin, J
2000-05-01
Centralization of treatment planning in a radiation therapy department is a realistic strategy to achieve an integrated and quality-controlled planning system, especially for institutions with numerous affiliations. The rapid evolution of computer hardware and software technology makes this a distinct possibility. However, the procedure of three-dimensional treatment planning involves a number of steps, such as: (1) input of patient computed tomography (CT) images and contour information; (2) interactions with local devices such as a film digitizer; and (3) output of beam information to be integrated with the record and verify the system. A full-fledged realization of the web-based centralized three-dimensional treatment planning system will require an extensive commercial development effort. We have developed and incorporated a web-based Timer/Monitor Unit (MU) program as a first step towards the full implementation of a centralized treatment planning system. The software application was developed in JAVA language. It uses the internet server and client technology. With one server that can handle multiple threads, it is a simple process to access the application anywhere on the network with an internet browser. Both the essential data needed for the calculation and the results are stored on the server, which centralizes the maintenance of the software and the storage of patient information.
Renormalization-group calculation of excitation properties for impurity models
Yoshida, M.; Whitaker, M. A.; Oliveira, L. N.
1990-05-01
The renormalization-group method developed by Wilson to calculate thermodynamical properties of dilute magnetic alloys is generalized to allow the calculation of dynamical properties of many-body impurity Hamiltonians. As a simple illustration, the impurity spectral density for the resonant-level model (i.e., the U=0 Anderson model) is computed. As a second illustration, for the same model, the longitudinal relaxation rate for a nuclear spin coupled to the impurity is calculated as a function of temperature.
Mitrikas, V G
2015-01-01
Monitoring of the radiation loading on cosmonauts requires calculation of absorbed dose dynamics with regard to the stay of cosmonauts in specific compartments of the space vehicle that differ in shielding properties and lack means of radiation measurement. The paper discusses different aspects of calculation modeling of radiation effects on human body organs and tissues and reviews the effective dose estimates for cosmonauts working in one or another compartment over the previous period of the International space station operation. It was demonstrated that doses measured by a real or personal dosimeters can be used to calculate effective dose values. Correct estimation of accumulated effective dose can be ensured by consideration for time course of the space radiation quality factor.
The calculation of thermodynamic properties of molecules
DEFF Research Database (Denmark)
van Speybroeck, Veronique; Gani, Rafiqul; Meier, Robert Johan
2010-01-01
Thermodynamic data are key in the understanding and design of chemical processes. Next to the experimental evaluation of such data, computational methods are valuable and sometimes indispensable tools in obtaining heats of formation and Gibbs free energies. The major toolboxes to obtain...... molecules the combination of group contribution methods with group additive values that are determined with the best available computational ab initio methods seems to be a viable alternative to obtain thermodynamic properties near chemical accuracy. New developments and full use of existing tools may lead...... such quantities by computation are quantum mechanical methods and group contribution methods. Although a lot of progress was made over the last decade, for the majority of chemical species we are still quite a bit away from what is often referred to as chemical accuracy, i.e.1 kcal mol-1. Currently, for larger...
Fontanot, Fabio; Silva, Laura; Monaco, Pierluigi; Skibba, Ramin; 10.1111/j.1365-2966.2008.14126.x
2009-01-01
The treatment of dust attenuation is crucial in order to compare the predictions of galaxy formation models with multiwavelength observations. Most past studies have either used simple analytic prescriptions or else full radiative transfer (RT) calculations. Here, we couple star formation histories and morphologies predicted by the semi-analytic galaxy formation model MORGANA with RT calculations from the spectrophotometric and dust code GRASIL to create a library of galaxy SEDs from the UV/optical through the far Infrared, and compare the predictions of the RT calculations with analytic prescriptions. We consider a low and high redshift sample, as well as an additional library constructed with empirical, non-cosmological star formation histories and simple (pure bulge or disc) morphologies. Based on these libraries, we derive fitting formulae for the effective dust optical depth as a function of galaxy physical properties such as metallicity, gas mass, and radius. We show that such fitting formulae can predi...
Fisenko, Anatoliy I
2014-01-01
Using the explicit form of the function to describe the average spectrum of the extragalactic far infrared background (FIRB) radiation measured by the COBE FIRAS instrument in the 0.15 - 2.4 THz frequency interval, the radiative and thermodynamic properties, such as the total emissivity, total radiation power per unit area, total energy density, number density of photons, Helmholtz free energy density, entropy density, heat capacity at constant volume, pressure, enthalpy density, and internal energy density are calculated. The calculated value of the total intensity received in the 0.15 - 2.4 THz frequency interval is 13.6 nW m^-2 sr^-1, and comprises about 19.4 % of the total intensity expected from the energy released by stellar nucleosynthesis over cosmic history. The radiative and thermodynamic functions of the extragalactic far infrared background (FIRB) radiation are calculated at redshift z = 1.5.
End-to-end calculation of the radiation characteristics of VVER-1000 spent fuel assemblies
Linge, I. I.; Mitenkova, E. F.; Novikov, N. V.
2012-12-01
The results of end-to-end calculation of the radiation characteristics of VVER-1000 spent nuclear fuel are presented. Details of formation of neutron and gamma-radiation sources are analyzed. Distributed sources of different types of radiation are considered. A comparative analysis of calculated radiation characteristics is performed with the use of nuclear data from different ENDF/B and EAF files and ANSI/ANS and ICRP standards.
Modeling radiative properties of nanoscale patterned wafers
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Temperature nonuniformity in rapid thermal processing of wafers is a critical problem facing the semiconductor industry. One cause of the problem is the nonuniform absorption of thermal radiation in patterned wafers where the optical properties vary across the wafer surface. This paper presents a parametric study of the radiative properties of patterned wafers, considering the effect of temperature, wavelength, and polarization. The finite-difference time-domain (FDTD) method is employed to examine the effect of various trench sizes on the radiative properties via numerically solving the Maxwell equations. The effective medium theory (EMT) is also used to help explain the absorptance prediction. The results show that in the cases with trench size variation, the resonance cavity effect may increase the absorptance as the trench width increases. And in the cases with trench size increasing at several different filling ratios, the absorptance does not change much at small filling ratio. The effects of the resonant cavity, diffraction, wave interferences on the spectral-directional absorptance were also discussed. This work is of great importance for optimization of advanced annealing techniques in semiconductor manufacturing.
3D Gray Radiative Properties of a Radiation Hydrodynamic Model of a YSO Accretion Shock
Ibgui, L.; de Sá, L.; Stehlé, C.; Chièze, J.-P.; Orlando, S.; Hubeny, I.; Lanz, T.; Matsakos, T.; González, M.; Bonito, R.
2014-09-01
We present preliminary results of radiative properties of a 1D gray radiation hydrodynamic (RHD) model of an accretion shock on a young stellar object (YSO). This model takes into account the transition between the collisional equilibrium regime (local thermodynamic equilibrium, LTE), and the coronal equilibrium regime. Based on the 1D planar structure, we built a 3D cylindrical one. Most notably, the post-shock region obtained in our case is far less extended (by a factor of 10 000) than the typical one obtained with models that assume gray optically thin radiative losses. Moreover, we find that the column is optically thin in its longitudinal dimension, and in the transverse dimension, except over an extremely narrow region (≲ 700 m). Consequently, still under the gray assumption, the photons emitted by the hot slab can propagate through the column and escape freely in all directions, including towards the chromosphere. The radiation flux has therefore components that are perpendicular to the accretion column, which demonstrates that a multidimensional (2D or 3D) radiative model is necessary for such a cylindrical structure. This study needs to be taken forward and expanded, by improving the radiative treatment of the RHD model, through relaxation of both the gray and the LTE approximations for the calculation of opacities, in order to clarify the structure of the post-shock region, which is a major source of emission probed by observations.
Energy Technology Data Exchange (ETDEWEB)
El Ammouri, F.; Plessier, R.; Till, M.; Marie, B.; Djavdan, E. [Air Liquide Centre de Recherche Claude Delorme, 78 - Jouy-en-Josas (France)
1996-12-31
Coupled reactive fluid dynamics and radiation calculations are performed in air and oxy-fuel furnaces using two gas radiative property models. The first one is the weighted sum of gray gases model (WSGG) and the second one is the correlated-k (CK) method which is a spectral model based on the cumulative distribution function of the absorption coefficient inside a narrow band. The WSGG model, generally used in industrial configurations, is less time consuming than the CK model. However it is found that it over-predicts radiative fluxes by about 12 % in industrial furnaces. (authors) 27 refs.
The libRadtran software package for radiative transfer calculations (version 2.0.1)
Emde, Claudia; Buras-Schnell, Robert; Kylling, Arve; Mayer, Bernhard; Gasteiger, Josef; Hamann, Ulrich; Kylling, Jonas; Richter, Bettina; Pause, Christian; Dowling, Timothy; Bugliaro, Luca
2016-05-01
libRadtran is a widely used software package for radiative transfer calculations. It allows one to compute (polarized) radiances, irradiance, and actinic fluxes in the solar and thermal spectral regions. libRadtran has been used for various applications, including remote sensing of clouds, aerosols and trace gases in the Earth's atmosphere, climate studies, e.g., for the calculation of radiative forcing due to different atmospheric components, for UV forecasting, the calculation of photolysis frequencies, and for remote sensing of other planets in our solar system. The package has been described in Mayer and Kylling (2005). Since then several new features have been included, for example polarization, Raman scattering, a new molecular gas absorption parameterization, and several new parameterizations of cloud and aerosol optical properties. Furthermore, a graphical user interface is now available, which greatly simplifies the usage of the model, especially for new users. This paper gives an overview of libRadtran version 2.0.1 with a focus on new features. Applications including these new features are provided as examples of use. A complete description of libRadtran and all its input options is given in the user manual included in the libRadtran software package, which is freely available at http://www.libradtran.org.
Equilibrium properties of blackbody radiation in Doubly Special Relativity
Chandra, Nitin; Vaibhav, Vinay
2016-01-01
Doubly Special Relativity (DSR) is an attempt to incorporate an observer independent energy/length scale in the relativistic theory. We study various thermodynamic properties of blackbody radiation in DSR. We find that the energy density, specific heat etc. follows usual acoustic phonon dynamics as has been well studied by Debye. Other thermodynamic quantities like pressure, entropy etc. has also been calculated. The usual Stefan-Boltzmann law gets modified. The phase-space measure is also expected to get modified for an exotic spacetime, which in turn leads to the modification of Planck energy density distribution and the Wien's displacement law.
Nuclear model calculations and their role in space radiation research
Townsend, L. W.; Cucinotta, F. A.; Heilbronn, L. H.
2002-01-01
Proper assessments of spacecraft shielding requirements and concomitant estimates of risk to spacecraft crews from energetic space radiation requires accurate, quantitative methods of characterizing the compositional changes in these radiation fields as they pass through thick absorbers. These quantitative methods are also needed for characterizing accelerator beams used in space radiobiology studies. Because of the impracticality/impossibility of measuring these altered radiation fields inside critical internal body organs of biological test specimens and humans, computational methods rather than direct measurements must be used. Since composition changes in the fields arise from nuclear interaction processes (elastic, inelastic and breakup), knowledge of the appropriate cross sections and spectra must be available. Experiments alone cannot provide the necessary cross section and secondary particle (neutron and charged particle) spectral data because of the large number of nuclear species and wide range of energies involved in space radiation research. Hence, nuclear models are needed. In this paper current methods of predicting total and absorption cross sections and secondary particle (neutrons and ions) yields and spectra for space radiation protection analyses are reviewed. Model shortcomings are discussed and future needs presented. c2002 COSPAR. Published by Elsevier Science Ltd. All right reserved.
Fisenko, Anatoliy I.; Lemberg, Vladimir
2015-11-01
There are several classes of materials and space objects for which the frequency dependence of the spectral emissivity is represented as a power series. Therefore, the study of the properties of thermal radiation for these real bodies is an important task for both fundamental science and industrial applications. The general analytical expressions for the thermal radiative and thermodynamic functions of a real body are obtained in a finite range of frequencies at different temperatures. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and total emissivity are expressed in terms of the polylogarithm functions. The obtained general expressions for the thermal radiative and thermodynamic functions are applied for the study of thermal radiation of liquid and solid zirconium carbide. These functions are calculated using experimental data for the frequency dependence of the normal spectral emissivity in the visible and near-infrared range at the melting (freezing) point. The gaps between the thermal radiative and thermodynamic functions of liquid and solid zirconium carbide are observed. The general analytical expressions obtained can easily be presented in the wavenumber domain.
Calculation of Wave Radiation Stress in Combination with Parabolic Mild Slope Equation
Institute of Scientific and Technical Information of China (English)
ZHENG Yonghong; SHEN Yongming; QIU Dahong
2000-01-01
A new method for the calculation of wave radiation stress is proposed by linking the expressions for wave radiation stress with the variables in the parabolic mild slope equation. The governing equations are solved numerically by the finite difference method. Numerical results show that the new method is accurate enough, can be efficiently solved with little programming effort, and can be applied to the calculation of wave radiation stress for large coastal areas.
Radiation properties of slot and dipole elements on layered substrates
Rogers, R. L.; Neikirk, D. P.
1989-06-01
Calculation results are presented for the radiation properties of slot and dipole antennas on electrically thick grounded dielectric substrates, with application to the development of mm-wave and far-IR imaging arrays. Factors considered in the selection of dieletric layers include the beam patterns, surface waves losses, and the type of element used. The effects of dielectric and ground plane losses are taken into account for the case of high-gain structures. Results for the efficiencies and beam patterns of three and five layer structures show that, in combination with a twin element configuration, both slot and dipole antennas can overcome the problem of losses to surface waves in the substrate and be made to efficiently radiate to air on these layered dielectric structures.
Radiative Transfer Code: Application to the calculation of PAR
Indian Academy of Sciences (India)
D Emmanuel; D Phillippe; C Malik
2000-12-01
The production of carbon in the ocean, the so-called primary production, depends on various physico- biological parameters: the biomass and nutrient amounts in oceans, the salinity and temperature of the water and the light available in the water column. We focus on the visible spectrum of the solar radiation defined as the Photosynthetically Active Radiation (PAR). We developed a model (Chami et al. 1997) to simulate the behavior of the solar beam in the atmosphere and the ocean. We first describe the theoretical basis of the code and the method we used to solve the radiative transfer equation (RTE): the successive orders of scattering (SO). The second part deals with a sensitivity study of the PAR just above and below the sea surface for various atmospheric conditions. In a cloudy sky, we computed a ratio between vector fluxes just above the sea surface and spherical fluxes just beneath the sea surface. When the optical thickness of the cloud increases this ratio remains constant and around 1.29. This parameter is convenient to convert vector flux at the sea surface as retrieved from satellite to PAR. Subsequently, we show how solar radiation as vector flux rather than PAR leads to an underestimate of the primary production up to 40% for extreme cases.
Fisenko, Anatoliy I.; Lemberg, Vladimir
2014-07-01
Using formula to describe the average spectrum of the extragalactic far infrared background (FIRB) radiation measured by the COBE FIRAS instrument in the 0.15-2.4 THz frequency interval at mean temperature T=18.5 K, the radiative and thermodynamic properties, such as the total emissivity, total radiation power per unit area, total energy density, number density of photons, Helmholtz free energy density, entropy density, heat capacity at constant volume, and pressure are calculated. The value for the total intensity received in the 0.15-2.4 THz frequency interval is equal to 13.6 nW m-2 sr-1. This value is about 19.4 % of the total intensity expected from the energy released by stellar nucleosynthesis over cosmic history. The radiative and thermodynamic functions of the extragalactic far infrared background (FIRB) radiation are calculated at redshift z=1.5.
Calculations in the Wheeler-Feynman Absorber Theory of Radiation.
Balaji, Kalathur Sreenivasan
One dimensional computer aided calculations were done to find the self-consistent solutions for various absorber configurations in the context of the Wheeler-Feynman Absorber theory, wherein every accelerating charge is assumed to produce a time symmetric combination of advanced and retarded fields. These calculations picked out the so called "outerface" solution for incomplete absorbers and showed that advanced as well as retarded signals interact with matter in the same manner as in the full retarded theory. Based on these calculations the Partridge experiment and the Schmidt-Newman experiment were ruled out as tests of the Absorber theory. An experiment designed to produce and detect advanced effects is proposed, based on more one-dimensional calculations.
Calculations in the Wheeler-Feynman absorber theory of radiation
Energy Technology Data Exchange (ETDEWEB)
Balaji, K.S.
1986-01-01
One dimensional computer aided calculations were done to find the self consistent solutions for various absorber configurations in the context of the Wheeler-Feynman absorber theory, wherein every accelerating charge is assumed to produce a time symmetric combination of advanced and retarded fields. These calculations picked out the so called outerface solution for incomplete absorbers and showed that advanced as well as retarded signals interact with matter in the same manner as in the full retarded theory. Based on these calculations, the Partridge experiment and the Schmidt-Newman experiment were ruled out as tests of the absorber theory. An experiment designed to produce and detect advanced effects is proposed, based on more one-dimensional calculations.
Calculations for Tera-Hertz (THZ) Radiation Sources
Energy Technology Data Exchange (ETDEWEB)
Hussein, Yasser A.; Spencer, James E.; /SLAC
2005-06-07
We explore possibilities for THz sources from 0.3-30 THz. While still inaccessible, this broad gap is even wider for advanced acceleration schemes extending from X or, at most, W band RF at the low end up to CO{sub 2} lasers. While the physical implementations of these two approaches are quite different, both are proving difficult to develop so that lower frequency, superconducting RF is currently preferred. Similarly, the validity of modeling techniques varies greatly over this range of frequencies but generally mandates coupling Maxwell's equations to the appropriate device transport physics for which there are many options. Here we study radiation from undulatory-shaped transmission lines using finite-difference, time-domain (FDTD) simulations. Also, we present Monte-Carlo techniques for pulse generation. Examples of THz sources demonstrating coherence are shown with the goal of optimizing on-chip THz radiators for applications that may lead to accelerators.
Interactive calculations of thermodynamics properties of minerals in VLab
Kelly, N.; da Silveira, P. R.; Wentzcovitch, R. M.
2009-12-01
We have developed a page within the VLab web site from which calculations of thermodynamics properties of minerals can be performed interactively. Previously published first principles calculations based on qhasiharmonic theory by our group have produced pressure dependent vibrational density of states (VDOSs). These calculations were costly and the essential information they produced, the VDOSs, are now stored on a database. They can be used to regenerate published results or calculate thermodynamics properties using specific user entered information (pressure and temperature range and grids, equation of state type, etc). Results are presented in numerical or graphics format (Gnuplot 4.2.2) that are interactively customized and downloadable. All codes behind the Web container are written in Java.
Derimian, Yevgeny; Dubovik, Oleg; Huang, Xin; Lapyonok, Tatyana; Litvinov, Pavel; Kostinski, Alex B.; Dubuisson, Philippe; Ducos, Fabrice
2016-05-01
The evaluation of aerosol radiative effect on broadband hemispherical solar flux is often performed using simplified spectral and directional scattering characteristics of atmospheric aerosol and underlying surface reflectance. In this study we present a rigorous yet fast computational tool that accurately accounts for detailed variability of both spectral and angular scattering properties of aerosol and surface reflectance in calculation of direct aerosol radiative effect. The tool is developed as part of the GRASP (Generalized Retrieval of Aerosol and Surface Properties) project. We use the tool to evaluate instantaneous and daily average radiative efficiencies (radiative effect per unit aerosol optical thickness) of several key atmospheric aerosol models over different surface types. We then examine the differences due to neglect of surface reflectance anisotropy, nonsphericity of aerosol particle shape and accounting only for aerosol angular scattering asymmetry instead of using full phase function. For example, it is shown that neglecting aerosol particle nonsphericity causes mainly overestimation of the aerosol cooling effect and that magnitude of this overestimate changes significantly as a function of solar zenith angle (SZA) if the asymmetry parameter is used instead of detailed phase function. It was also found that the nonspherical-spherical differences in the calculated aerosol radiative effect are not modified significantly if detailed BRDF (bidirectional reflectance distribution function) is used instead of Lambertian approximation of surface reflectance. Additionally, calculations show that usage of only angular scattering asymmetry, even for the case of spherical aerosols, modifies the dependence of instantaneous aerosol radiative effect on SZA. This effect can be canceled for daily average values, but only if sun reaches the zenith; otherwise a systematic bias remains. Since the daily average radiative effect is obtained by integration over a range
Sakamoto, Y
2002-01-01
In the prevention of nuclear disaster, there needs the information on the dose equivalent rate distribution inside and outside the site, and energy spectra. The three dimensional radiation transport calculation code is a useful tool for the site specific detailed analysis with the consideration of facility structures. It is important in the prediction of individual doses in the future countermeasure that the reliability of the evaluation methods of dose equivalent rate distribution and energy spectra by using of Monte Carlo radiation transport calculation code, and the factors which influence the dose equivalent rate distribution outside the site are confirmed. The reliability of radiation transport calculation code and the influence factors of dose equivalent rate distribution were examined through the analyses of critical accident at JCO's uranium processing plant occurred on September 30, 1999. The radiation transport calculations including the burn-up calculations were done by using of the structural info...
Using electron microscopy to calculate optical properties of biological samples
Wu, Wenli; Radosevich, Andrew J.; Eshein, Adam; Nguyen, The-Quyen; Yi, Ji; Cherkezyan, Lusik; Roy, Hemant K.; Szleifer, Igal; Backman, Vadim
2016-01-01
The microscopic structural origins of optical properties in biological media are still not fully understood. Better understanding these origins can serve to improve the utility of existing techniques and facilitate the discovery of other novel techniques. We propose a novel analysis technique using electron microscopy (EM) to calculate optical properties of specific biological structures. This method is demonstrated with images of human epithelial colon cell nuclei. The spectrum of anisotropy...
On plasma radiative properties in stellar conditions
Turck-Chièze, S; Gilles, D; Loisel, G; Piau, L; 10.1016/j.hedp.2009.06.007
2012-01-01
The knowledge of stellar evolution is evolving quickly thanks to an increased number of opportunities to scrutinize the stellar internal plasma properties by stellar seismology and by 1D and 3D simulations. These new tools help us to introduce the internal dynamical phenomena in stellar modeling. A proper inclusion of these processes supposes a real confidence in the microscopic physics used, partly checked by solar or stellar acoustic modes. In the present paper we first recall which fundamental physics has been recently verified by helioseismology. Then we recall that opacity is an important ingredient of the secular evolution of stars and we point out why it is necessary to measure absorption coefficients and degrees of ionization in the laboratory for some well identified astrophysical conditions. We examine two specific experimental conditions which are accessible to large laser facilities and are suitable to solve some interesting questions of the stellar community: are the solar internal radiative inte...
The spacing calculator software—A Visual Basic program to calculate spatial properties of lineaments
Ekneligoda, Thushan C.; Henkel, Herbert
2006-05-01
A software tool is presented which calculates the spatial properties azimuth, length, spacing, and frequency of lineaments that are defined by their starting and ending co-ordinates in a two-dimensional (2-D) planar co-ordinate system. A simple graphical interface with five display windows creates a user-friendly interactive environment. All lineaments are considered in the calculations, and no secondary sampling grid is needed for the elaboration of the spatial properties. Several rule-based decisions are made to determine the nearest lineament in the spacing calculation. As a default procedure, the programme defines a window that depends on the mode value of the length distribution of the lineaments in a study area. This makes the results more consistent, compared to the manual method of spacing calculation. Histograms are provided to illustrate and elaborate the distribution of the azimuth, length and spacing. The core of the tool is the spacing calculation between neighbouring parallel lineaments, which gives direct information about the variation of block sizes in a given category of structures. The 2-D lineament frequency is calculated for the actual area that is occupied by the lineaments.
A uniform representation in the calculation of seismic radiation efficiency and rupture speed
Institute of Scientific and Technical Information of China (English)
LI Yan-Heng; SHI Bao-Ping; ZHANG Jian
2008-01-01
According to energy partition principle, we have derived a generalized formula used to calculate the radiation efficiency. It overcomes the numerical errors involved in the estimation of radiation efficiency caused by the uncertainties owe to the different frictional mechanisms which is used to describe the earthquake faulting. Using real seismic data published in the previous studies, we have recalculated the radiation efficiency with associated to the different frictional mechanisms, and compared with previous results lack of consideration of frictional mechanism. The results indicate that, based on the new formula, the radiation efficiency we have estimated is always less than 1, and the unphysical conclusion of radiation efficiency greater than 1 is avoided completely.
Kopparla, P.; Natraj, V.; Shia, R. L.; Spurr, R. J. D.; Crisp, D.; Yung, Y. L.
2015-12-01
Radiative transfer (RT) computations form the engine of atmospheric retrieval codes. However, full treatment of RT processes is computationally expensive, prompting usage of two-stream approximations in current exoplanetary atmospheric retrieval codes [Line et al., 2013]. Natraj et al. [2005, 2010] and Spurr and Natraj [2013] demonstrated the ability of a technique using principal component analysis (PCA) to speed up RT computations. In the PCA method for RT performance enhancement, empirical orthogonal functions are developed for binned sets of inherent optical properties that possess some redundancy; costly multiple-scattering RT calculations are only done for those few optical states corresponding to the most important principal components, and correction factors are applied to approximate radiation fields. Kopparla et al. [2015, in preparation] extended the PCA method to a broadband spectral region from the ultraviolet to the shortwave infrared (0.3-3 micron), accounting for major gas absorptions in this region. Here, we apply the PCA method to a some typical (exo-)planetary retrieval problems. Comparisons between the new model, called Universal Principal Component Analysis Radiative Transfer (UPCART) model, two-stream models and line-by-line RT models are performed, for spectral radiances, spectral fluxes and broadband fluxes. Each of these are calculated at the top of the atmosphere for several scenarios with varying aerosol types, extinction and scattering optical depth profiles, and stellar and viewing geometries. We demonstrate that very accurate radiance and flux estimates can be obtained, with better than 1% accuracy in all spectral regions and better than 0.1% in most cases, as compared to a numerically exact line-by-line RT model. The accuracy is enhanced when the results are convolved to typical instrument resolutions. The operational speed and accuracy of UPCART can be further improved by optimizing binning schemes and parallelizing the codes, work
Ackerman, Thomas P.; Kinne, Stefan A.; Heymsfield, Andrew J.; Valero, Francisco P. J.
1990-01-01
Several aircraft were employed during the FIRE Cirrus IFO in order to make nearly simultaneous observations of cloud properties and fluxes. A segment of the flight data collected on 28 October 1988 during which the NASA Ames ER-2 overflew the NCAR King Air was analyzed. The ER-2 flew at high altitude making observations of visible and infrared radiances and infrared flux and cloud height and thickness. During this segment, the King Air flew just above the cloud base making observations of ice crystal size and shape, local meteorological variables, and infrared fluxes. While the two aircraft did not collect data exactly coincident in space and time, they did make observations within a few minutes of each other. For this case study, the infrared radiation balance of the cirrus layer is of primary concern. Observations of the upwelling 10 micron radiance, made from the ER-2, can be used to deduce the 10 micron optical depth of the layer. The upwelling broadband infrared flux is also measured from the ER-2. At the same time, the upwelling and downwelling infrared flux at the cloud base is obtained from the King Air measurements. Information on cloud microphysics is also available from the King Air. Using this data in conjunction with atmospheric temperature and humidity profiles from local radiosondes, the necessary inputs for an infrared radiative transfer model can be developed. Infrared radiative transfer calculations are performed with a multispectral two-stream model. The model fluxes at the cloud base and at 19 km are then compared with the aircraft observations to determine whether the model is performing well. Cloud layer heating rates can then be computed from the radiation exchange.
Energy Technology Data Exchange (ETDEWEB)
Napier, B.A.; Kennedy, W.E. Jr.; Soldat, J.K.
1980-03-01
A computer program, PABLM, was written to facilitate the calculation of internal radiation doses to man from radionuclides in food products and external radiation doses from radionuclides in the environment. This report contains details of mathematical models used and calculational procedures required to run the computer program. Radiation doses from radionuclides in the environment may be calculated from deposition on the soil or plants during an atmospheric or liquid release, or from exposure to residual radionuclides in the environment after the releases have ended. Radioactive decay is considered during the release of radionuclides, after they are deposited on the plants or ground, and during holdup of food after harvest. The radiation dose models consider several exposure pathways. Doses may be calculated for either a maximum-exposed individual or for a population group. The doses calculated are accumulated doses from continuous chronic exposure. A first-year committed dose is calculated as well as an integrated dose for a selected number of years. The equations for calculating internal radiation doses are derived from those given by the International Commission on Radiological Protection (ICRP) for body burdens and MPC's of each radionuclide. The radiation doses from external exposure to contaminated water and soil are calculated using the basic assumption that the contaminated medium is large enough to be considered an infinite volume or plane relative to the range of the emitted radiations. The equations for calculations of the radiation dose from external exposure to shoreline sediments include a correction for the finite width of the contaminated beach.
Institute of Scientific and Technical Information of China (English)
CHEN Ming-Zhi; HE Jian-Hua
2009-01-01
Undulators are key devices to produce brilliant synchrotron radiation at the synchrotron radiation facilities.In this paper we present a numerical computing method,including the computing program that has been developed to calculate the spontaneous radiation emitted from relativistic electrons in undulators by simulating the electrons' trajectory.The effects of electron beam emittance and energy spread have also been taken into account.Comparing with other computing methods available at present,this method has a few advantages with respect to several aspects.It can adopt any measured or arbitrarily simulated 3D magnetic field and arbitrary electron beam pattern for the calculation and it's able to analyze undulators of any type of magnetic structure.It's expected to predict precisely the practical radiation spectrum.The calculation results of a short period in-vacuum undulator and an EllipticaUy Polarized Undulator (EPU) at Shanghai Synchrotron Radiation Facility (SSRF) are presented as examples.
Analytical Calculation of Radiative Corrections of a THDM Potential
Díaz, Enrique
2016-01-01
We obtain a closed form effective potential at the one-loop level of a Two Higgs Doublet Model. Through the loop expansion we reproduce the expression presented by Weinberg and Coleman, showing explicitly every step involved in the calculation. The formalism is then extended to include interaction terms between two scalar doublets and a final expression of the one-loop level contributions is presented.
Using electron microscopy to calculate optical properties of biological samples.
Wu, Wenli; Radosevich, Andrew J; Eshein, Adam; Nguyen, The-Quyen; Yi, Ji; Cherkezyan, Lusik; Roy, Hemant K; Szleifer, Igal; Backman, Vadim
2016-11-01
The microscopic structural origins of optical properties in biological media are still not fully understood. Better understanding these origins can serve to improve the utility of existing techniques and facilitate the discovery of other novel techniques. We propose a novel analysis technique using electron microscopy (EM) to calculate optical properties of specific biological structures. This method is demonstrated with images of human epithelial colon cell nuclei. The spectrum of anisotropy factor g, the phase function and the shape factor D of the nuclei are calculated. The results show strong agreement with an independent study. This method provides a new way to extract the true phase function of biological samples and provides an independent validation for optical property measurement techniques.
Energy Technology Data Exchange (ETDEWEB)
Dalzell, M.T.J. [Sylvia Fedoruk Canadian Centre for Nuclear Innovation, Saskatoon, Saskatchewan (Canada)
2016-06-15
Concerns arising from misunderstandings about radiation are often cited as a main reason for public antipathy towards nuclear development and impede decision-making by governments and individuals. A lack of information about everyday sources of radiation exposure that is accessible, relatable and factual contributes to the problem. As part of its efforts to be a fact-based source of information on nuclear issues, the Sylvia Fedoruk Canadian Centre for Nuclear Innovation has developed an on-line Canadian Radiation Dose Calculator as a tool to provide context about common sources of radiation. This paper discusses the development of the calculator and describes how the Fedoruk Centre is using it and other tools to support public engagement on nuclear topics. (author)
Sen, S.; Caranza, S.; Bhattacharya, M.; Makel, D. B.
2006-01-01
The 2 primary requirements of a Martian habitat structure include sufficient structural integrity and effective radiation shielding. In addition, the capability to synthesize such building materials primarily from in-situ resources would significantly reduce the cost associated with transportation of such materials and structures from earth. To demonstrate the feasibility of such an approach we have fabricated samples in the laboratory using simulated in-situ resources, evaluated radiation shielding effectiveness using radiation transport codes and radiation test data, and conducted mechanical properties testing. In this paper we will present experimental results that demonstrate the synthesis of polyethylene from a simulated Martian atmosphere and the fabrication of a composite material using simulated Martian regolith with polyethylene as the binding material. Results from radiation transport calculations and data from laboratory radiation testing using a 500 MeV/nucleon Fe beam will be discussed. Mechanical properties of the proposed composite as a function of composition and processing parameters will also be presented.
Atmospheric radiative transfer parametrization for solar energy yield calculations on buildings
Wagner, Jochen E
2015-01-01
In this paper the practical approach to evaluate the incoming solar radiation on buildings based on atmospheric composition and cloud cover is presented. The effects of absorption and scattering due to atmospheric composition is taken into account to calculate, using radiative transfer models, the net incoming solar radiation at surface level. A specific validation of the Alpine Region in Europe is presented with a special focus on the region of South Tyrol.
Direct method for calculating temperature-dependent transport properties
Liu, Yi; Yuan, Zhe; Wesselink, R. J. H.; Starikov, Anton A.; van Schilfgaarde, Mark; Kelly, Paul J.
2015-06-01
We show how temperature-induced disorder can be combined in a direct way with first-principles scattering theory to study diffusive transport in real materials. Excellent (good) agreement with experiment is found for the resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are calculated from first principles. For Fe, the agreement with experiment is limited by how well the magnetization (of itinerant ferromagnets) can be calculated as a function of temperature. By introducing a simple Debye-like model of spin disorder parameterized to reproduce the experimental magnetization, the temperature dependence of the average resistivity, the anisotropic magnetoresistance, and the spin polarization of a Ni80Fe20 alloy are calculated and found to be in good agreement with existing data. Extension of the method to complex, inhomogeneous materials as well as to the calculation of other finite-temperature physical properties within the adiabatic approximation is straightforward.
Cox, J.A.M.; Groot, S.R. de; Hartogh, Chr.D.
1953-01-01
In this note the theoretical results for the angular distribution of γ-radiation emitted by oriented radioactive nuclei are applied to the case of 58Co nuclei. The angular distribution function of the γ-radiation has been calculated for an arbitrary degree of nuclear orientation and in dependence of
Semi-random simulation method for calculating 3-D radiation transfer problems in cavity
Institute of Scientific and Technical Information of China (English)
冯庭桂; 赖东显
1996-01-01
One of the most important issues in inertial confinement fusion (ICF) is to study the uniformity of the radiation field around the implosion pellet containing fuel.To this end,a numerical method linking Monte Carlo with iteration method is presented for calculating the radiation transfer problems in a cavity.The detail of the calculation scheme is described and some numerical examples are also given.
Radiative properties of materials with surface scattering or volume scattering: A review
Institute of Scientific and Technical Information of China (English)
Qunzhi ZHU; Hyunjin LEE; Zhuomin M. ZHANG
2009-01-01
Radiative properties of rough surfaces, parti-culate media and porous materials are important in thermal engineering and many other applications. These properties are often needed for calculating heat transfer between surfaces and volume elements in participating media, as well as for accurate radiometric temperature measure-ments. In this paper, recent research on scattering of thermal radiation by rough surfaces, fibrous insulation, soot, aerogel, biological materials, and polytetrafluor-oethylene (PTFE) is reviewed. Both theoretical modeling and experimental investigation are discussed. Rigorous solutions and approximation methods for surface scattering and volume scattering are described. The approach of using measured surface roughness statistics in Monte Carlo simulations to predict radiative properties of rough surfaces is emphasized. The effects of various parameters on the radiative properties of particulate media and porous materials are summarized.
Energy Technology Data Exchange (ETDEWEB)
Renner, Franziska [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany)
2016-11-01
Monte Carlo simulations are regarded as the most accurate method of solving complex problems in the field of dosimetry and radiation transport. In (external) radiation therapy they are increasingly used for the calculation of dose distributions during treatment planning. In comparison to other algorithms for the calculation of dose distributions, Monte Carlo methods have the capability of improving the accuracy of dose calculations - especially under complex circumstances (e.g. consideration of inhomogeneities). However, there is a lack of knowledge of how accurate the results of Monte Carlo calculations are on an absolute basis. A practical verification of the calculations can be performed by direct comparison with the results of a benchmark experiment. This work presents such a benchmark experiment and compares its results (with detailed consideration of measurement uncertainty) with the results of Monte Carlo calculations using the well-established Monte Carlo code EGSnrc. The experiment was designed to have parallels to external beam radiation therapy with respect to the type and energy of the radiation, the materials used and the kind of dose measurement. Because the properties of the beam have to be well known in order to compare the results of the experiment and the simulation on an absolute basis, the benchmark experiment was performed using the research electron accelerator of the Physikalisch-Technische Bundesanstalt (PTB), whose beam was accurately characterized in advance. The benchmark experiment and the corresponding Monte Carlo simulations were carried out for two different types of ionization chambers and the results were compared. Considering the uncertainty, which is about 0.7 % for the experimental values and about 1.0 % for the Monte Carlo simulation, the results of the simulation and the experiment coincide.
Monte Carlo calculation of radiation energy absorbed in plastic scintillators
Energy Technology Data Exchange (ETDEWEB)
Mainardi, R.T.; Bonzi, E.V. [Universidad Nacional de Cordoba (Argentina). Facultad de Matematica, Astronomia y Fisica
1995-05-01
Monte Carlo calculations of the rate of absorbed energy from a photon beam were carried out to compare the response of commercial plastic scintillators with that of air in the energy region below 1 MeV. We have found that for photon energies above 100 keV, the response of different kinds of plastics is proportional to that of air, while below this value of energy, we have obtained differences between the responses of plastics and air. In a literature search, we have also found discrepancies with other authors as well as among them. In this paper, we investigate the possibilities of eliminating these differences and explaining discrepancies. We found that doping a plastic scintillator with silicon makes the composite materials behave like air from 2 keV up to 600 keV, making the ratio of absorbed energy constant. This energy region is of interest in radiology and surface radiotherapy and we conclude that a plastic scintillator with truly air-equivalent behavior is of importance to carry out more precise dosimetry. Other elements such as fluorine and magnesium were also considered, but silicon was found to be more appropriate due to its greater atomic number and its interchangeability with carbon in hydrocarbon molecules. (author).
Calculated disturbances for evaluation of dynamical properties of freight cars
Directory of Open Access Journals (Sweden)
I.A. Mashchenko
2013-08-01
Full Text Available Purpose. To form realizations of the calculated disturbances for studying the dynamic properties of railway vehicles. Methodology. Records of the track-test car for one of the typical track sections of the Pridneprovsk railroad are the basic data for building the disturbance components. To derive the true geometric parameters of the railway gauge the records of the track-test car using a double-point metering circuit are transformed considering the transfer function of the measuring system. A model of the calculated disturbances is presented as the four components: a symmetric vertical irregularity determined as a semi-sum of vertical irregularities of the right and left rails; an oblique-symmetric vertical irregularity of the track determined as a semi-difference of vertical irregularities of the right and left rails; horizontal irregularities of the right and left rails. Acceptability criterion of the constructed disturbances is a relationship between the values of the dynamical properties factors of cars and the corresponding experimental data. Findings. The three techniques for the calculated disturbances forming are proposed. The first technique uses records of the track-test car for the track with a sufficiently high amount for given track conditions as components of the calculated disturbances. In so doing symmetrical vertical components of disturbances resulting from records of settling are corrected with the mass and stiffness parameters of the car under consideration. The second technique uses building and applying the theoretical realizations of irregularities corresponding to a real track according to a spectral analysis. The third technique ensures a polyharmonic model of disturbances, the parameters of which are the values of the basic frequencies and amplitudes that are typical for irregularities of a railway track. A possibility of practical applying of the constructed models of disturbances are presented using an example for
Simulative calculation of bromo-polystyrene mechanical properties
Wang Chao; Tang Yong Jian
2002-01-01
The non-crystal model of polystyrene and bromo-polystyrene was established with the help of simulative software in the computer. DREIDING was chosen as force field and its parameters is modified according to the published data. Based on the calculation results and other published data the mechanism properties of polystyrene and bromo-polystyrene, such as bulk module, Yong's module and Poisson's ratios, were discussed
Neutron spectra and dose equivalents calculated in tissue for high-energy radiation therapy
Energy Technology Data Exchange (ETDEWEB)
Kry, Stephen F.; Howell, Rebecca M.; Salehpour, Mohammad; Followill, David S. [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States)
2009-04-15
Neutrons are by-products of high-energy radiation therapy and a source of dose to normal tissues. Thus, the presence of neutrons increases a patient's risk of radiation-induced secondary cancer. Although neutrons have been thoroughly studied in air, little research has been focused on neutrons at depths in the patient where radiosensitive structures may exist, resulting in wide variations in neutron dose equivalents between studies. In this study, we characterized properties of neutrons produced during high-energy radiation therapy as a function of their depth in tissue and for different field sizes and different source-to-surface distances (SSD). We used a previously developed Monte Carlo model of an accelerator operated at 18 MV to calculate the neutron fluences, energy spectra, quality factors, and dose equivalents in air and in tissue at depths ranging from 0.1 to 25 cm. In conjunction with the sharply decreasing dose equivalent with increased depth in tissue, the authors found that the neutron energy spectrum changed drastically as a function of depth in tissue. The neutron fluence decreased gradually as the depth increased, while the average neutron energy decreased sharply with increasing depth until a depth of approximately 7.5 cm in tissue, after which it remained nearly constant. There was minimal variation in the quality factor as a function of depth. At a given depth in tissue, the neutron dose equivalent increased slightly with increasing field size and decreasing SSD; however, the percentage depth-dose equivalent curve remained constant outside the primary photon field. Because the neutron dose equivalent, fluence, and energy spectrum changed substantially with depth in tissue, we concluded that when the neutron dose equivalent is being determined at a depth within a patient, the spectrum and quality factor used should be appropriate for depth rather than for in-air conditions. Alternately, an appropriate percent depth-dose equivalent curve
Radiation Re-solution Calculation in Uranium-Silicide Fuels
Energy Technology Data Exchange (ETDEWEB)
Matthews, Christopher [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Andersson, Anders David Ragnar [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Unal, Cetin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-01-27
The release of fission gas from nuclear fuels is of primary concern for safe operation of nuclear power plants. Although the production of fission gas atoms can be easily calculated from the fission rate in the fuel and the average yield of fission gas, the actual diffusion, behavior, and ultimate escape of fission gas from nuclear fuel depends on many other variables. As fission gas diffuses through the fuel grain, it tends to collect into intra-granular bubbles, as portrayed in Figure 1.1. These bubbles continue to grow due to absorption of single gas atoms. Simultaneously, passing fission fragments can cause collisions in the bubble that result in gas atoms being knocked back into the grain. This so called “re-solution” event results in a transient equilibrium of single gas atoms within the grain. As single gas atoms progress through the grain, they will eventually collect along grain boundaries, creating inter-granular bubbles. As the inter-granular bubbles grow over time, they will interconnect with other grain-face bubbles until a pathway is created to the outside of the fuel surface, at which point the highly pressurized inter-granular bubbles will expel their contents into the fuel plenum. This last process is the primary cause of fission gas release. From the simple description above, it is clear there are several parameters that ultimately affect fission gas release, including the diffusivity of single gas atoms, the absorption and knockout rate of single gas atoms in intra-granular bubbles, and the growth and interlinkage of intergranular bubbles. Of these, the knockout, or re-solution rate has an particularly important role in determining the transient concentration of single gas atoms in the grain. The re-solution rate will be explored in the following sections with regards to uranium-silicide fuels in order to support future models of fission gas bubble behavior.
Fisenko, Anatoliy I.; Lemberg, Vladimir
2015-07-01
Using the three-component spectral model describing the FIRAS average continuum spectra, the exact analytical expressions for thermodynamic and radiative functions of Galactic far-infrared radiation are obtained. The COBE FIRAS instrument data in the 0.15-2.88 THz frequency interval at the mean temperatures of T1 = 17.72 K, T2 = 14 K and T3 = 6.73 K are used for calculating the radiative and thermodynamic functions, such as the total radiation power per unit area, total energy density, total emissivity, number density of photons, Helmholtz free energy density, entropy density, heat capacity at constant volume and pressure for the warm, intermediate-temperature and very cold components of the Galactic continuum spectra. The generalized Stefan-Boltzmann law for warm, intermediate-temperature and very cold components is constructed. The temperature dependence of each component is determined by the formula IS-B(T) = σ‧T6. This result is important when we construct the cosmological models of radiative transfer that can be applied inside the Galaxy. Within the framework of the three-component spectral model, the total number of photons in our Galaxy and the total radiation power (total luminosity) emitted from a surface of the Galaxy are calculated. Their values are NGtotal = 1.3780 × 1068 and IGtotal(T) = 1.0482 × 1036 W. Other radiative and thermodynamic properties of the Galactic far-infrared radiation (photon gas) of the Galaxy are calculated. The expressions for astrophysical parameters, such as the entropy density/Boltzmann constant and number density of the Galactic far-infrared photons are obtained. We assume that the obtained analytical expressions for thermodynamic and radiative functions may be useful for describing the continuum spectra of the far-infrared radiation for other galaxies.
Consistency in Perturbative Calculations and Radiatively Induced Lorentz and CPT Violations
Battistel, O A
2002-01-01
The origin of the radiatively induced Lorentz and CPT violations, in perturbative evaluations, of an extended version of QED, is investigated. Using a very general calculational method, concerning the manipulations and calculations involving divergent amplitudes, we clearly identify the possible sources of contributions for the violating terms. We show that consistency in the perturbative calculations, in a broader sense, leaves no room for the existence of radiatively induced contributions which is in accordance with what was previously conjectured and recently advocated by some authors supported on general arguments.
Consistency in perturbative calculations and radiatively induced Lorentz and CPT violations
Energy Technology Data Exchange (ETDEWEB)
Battistel, O.A. [Department of Physics-CCNE, Universidade Federal de Santa Maria, Santa Maria, RS (Brazil)]. E-mail: orimar@ccne.ufsm.br; Dallabona, G. [Department of Physics-ICEx, Universidade Federal de Minas Gerais, Belo Horizonte (Brazil)]. E-mail: dalla@fisica.ufmg.br
2002-08-01
The origin of the radiatively induced Lorentz and CPT violations, in perturbative evaluations, of an extended version of QED, is investigated. Using a very general calculational method, concerning the manipulations and calculations involving divergent amplitudes, we clearly identify the possible sources of contributions for the violating terms. We show that consistency in the perturbative calculations, in a broader sense, leaves no room for the existence of radiatively induced contributions, which is in accordance with what was previously conjectured and recently advocated by some authors supported on general arguments. (author). Letter-to-the-editor.
Radiation properties and emissivity parameterization of high level thin clouds
Wu, M.-L. C.
1984-01-01
To parameterize emissivity of clouds at 11 microns, a study has been made in an effort to understand the radiation field of thin clouds. The contributions to the intensity and flux from different sources and through different physical processes are calculated by using the method of successive orders of scattering. The effective emissivity of thin clouds is decomposed into the effective absorption emissivity, effective scattering emissivity, and effective reflection emissivity. The effective absorption emissivity depends on the absorption and emission of the cloud; it is parameterized in terms of optical thickness. The effective scattering emissivity depends on the scattering properties of the cloud; it is parameterized in terms of optical thickness and single scattering albedo. The effective reflection emissivity follows the similarity relation as in the near infrared cases. This is parameterized in terms of the similarity parameter and optical thickness, as well as the temperature difference between the cloud and ground.
Huege, Tim; Falcke, Heino; Ludwig, Marianne
2011-01-01
We present the "endpoint" formalism for the calculation of electromagnetic radiation and illustrate its applications in astroparticle physics. We use the formalism to explain why the coherent radiation from the Askaryan effect is not in general Cherenkov radiation, as the emission directly results from the time-variation of the net charge in the particle shower. Secondly, we illustrate how the formalism has been applied in the air shower radio emission code REAS3 to unify the microscopic and macroscopic views of radio emission from extensive air showers. Indeed, the formalism is completely universal and particularly well-suited for implementation in Monte Carlo codes in the time- and frequency-domains. It easily reproduces well-known "classical mechanisms" such as synchrotron radiation, Vavilov-Cherenkov radiation and transition radiation in the adequate limits, but has the advantage that it continues to work in realistic, complex situations, where the "classical mechanisms" tend to no longer apply and adheri...
[Calculation and simulation on infrared radiation of hot jet from engine].
Li, Jian-Xun; Tong, Zhong-Xiang; Wang, Chao-Zhe; Tong, Qi; Li, He; Zhang, Zhi-Bo
2013-01-01
Spectral distribution of infrared radiation from plume by the method to calculate infrared radiance of the gaze direction in small sight field was calculated. Based on numerical value and form of radiative transfer equation, infrared radiant intensity of the gaze direction was calculated using the Malkmus statistical narrow-band model and CG approach. Flow field and mole fraction distribution were simulated using a FLUENT computational fluid dynamic (CFD) software. Infrared imaging simulation model of hot jet was established. The hot jet's infrared images of liquid rocket engine were generated. The results demonstrate that the method can detect well-resolved fine structure of flow field. And the model is also applicable to calculation and simulation on infrared radiation of hot jet from engine.
Membrane Protein Properties Revealed through Data-Rich Electrostatics Calculations.
Marcoline, Frank V; Bethel, Neville; Guerriero, Christopher J; Brodsky, Jeffrey L; Grabe, Michael
2015-08-04
The electrostatic properties of membrane proteins often reveal many of their key biophysical characteristics, such as ion channel selectivity and the stability of charged membrane-spanning segments. The Poisson-Boltzmann (PB) equation is the gold standard for calculating protein electrostatics, and the software APBSmem enables the solution of the PB equation in the presence of a membrane. Here, we describe significant advances to APBSmem, including full automation of system setup, per-residue energy decomposition, incorporation of PDB2PQR, calculation of membrane-induced pKa shifts, calculation of non-polar energies, and command-line scripting for large-scale calculations. We highlight these new features with calculations carried out on a number of membrane proteins, including the recently solved structure of the ion channel TRPV1 and a large survey of 1,614 membrane proteins of known structure. This survey provides a comprehensive list of residues with large electrostatic penalties for being embedded in the membrane, potentially revealing interesting functional information.
Shaftan, T; Hulbert, S L; Berman, L
2008-07-01
In this article the calculation of brightness and flux for two insertion devices of the 2.8 GeV X-ray storage ring at the NSLS is discussed. The radiation properties from the X25 linearly polarized wiggler and the new X25 short-period undulator are compared at a fixed photon energy (11.3 keV) corresponding to emission from the fifth harmonic of the short-period undulator. For this computation, three commonly available synchrotron radiation programs are used. The capabilities of each of these codes are briefly discussed, and their range of applicability are commented on. It is concluded that special care is needed when modeling the radiation of the classes of insertion devices considered here.
Camps, Peter; Bianchi, Simone; Lunttila, Tuomas; Pinte, Christophe; Natale, Giovanni; Juvela, Mika; Fischera, Joerg; Fitzgerald, Michael P; Gordon, Karl; Baes, Maarten; Steinacker, Juergen
2015-01-01
We define an appropriate problem for benchmarking dust emissivity calculations in the context of radiative transfer (RT) simulations, specifically including the emission from stochastically heated dust grains. Our aim is to provide a self-contained guide for implementors of such functionality, and to offer insights in the effects of the various approximations and heuristics implemented by the participating codes to accelerate the calculations. The benchmark problem definition includes the optical and calorimetric material properties, and the grain size distributions, for a typical astronomical dust mixture with silicate, graphite and PAH components; a series of analytically defined radiation fields to which the dust population is to be exposed; and instructions for the desired output. We process this problem using six RT codes participating in this benchmark effort, and compare the results to a reference solution computed with the publicly available dust emission code DustEM. The participating codes implement...
Efficient calculation of dissipative quantum transport properties in semiconductor nanostructures
Energy Technology Data Exchange (ETDEWEB)
Greck, Peter
2012-11-26
We present a novel quantum transport method that follows the non-equilibrium Green's function (NEGF) framework but side steps any self-consistent calculation of lesser self-energies by replacing them by a quasi-equilibrium expression. We termed this method the multi-scattering Buettiker-Probe (MSB) method. It generalizes the so-called Buettiker-Probe model but takes into account all relevant individual scattering mechanisms. It is orders of magnitude more efficient than a fully selfconsistent non-equilibrium Green's function calculation for realistic devices, yet accurately reproduces the results of the latter method as well as experimental data. This method is fairly easy to implement and opens the path towards realistic three-dimensional quantum transport calculations. In this work, we review the fundamentals of the non-equilibrium Green's function formalism for quantum transport calculations. Then, we introduce our novel MSB method after briefly reviewing the original Buettiker-Probe model. Finally, we compare the results of the MSB method to NEGF calculations as well as to experimental data. In particular, we calculate quantum transport properties of quantum cascade lasers in the terahertz (THz) and the mid-infrared (MIR) spectral domain. With a device optimization algorithm based upon the MSB method, we propose a novel THz quantum cascade laser design. It uses a two-well period with alternating barrier heights and complete carrier thermalization for the majority of the carriers within each period. We predict THz laser operation for temperatures up to 250 K implying a new temperature record.
Methodology for calculation of radiation doses in the environs from nuclear fuel cycle facilities
Energy Technology Data Exchange (ETDEWEB)
Soldat, J.K.
1976-08-01
Comparison of the impacts of various nuclear fuel cycle alternatives includes the evaluation of the radiological impacts. To evaluate the radiological impacts of fuel cycle alternatives, exposure to man must first be identified. The pathways of consequence by which man can be exposed to radiation from a nuclear facility are listed and are grouped into those associated with gaseous effluents, those associated with liquid effluents, and those involving exposure to direct radiation from the facility or from transportation of radioactive materials to or from the facility. Calculations for each pathway were made for those selected organs which could potentially receive the highest radiation dose. Some of the programs developed for calculating radiation doses from radionuclides in the environment are described. (CH)
Zhang, H.; Yang, D.; Song, P.; Zou, S.; Zhao, Y.; Li, S.; Li, Z.; Guo, L.; Wang, F.; Zheng, W.; Gu, P.; Pei, W.; Zhu, S.; Jiang, S.; Ding, Y.
2016-08-01
The symmetric radiation drive is essential to the capsule implosion in the indirect drive fusion but is hard to achieve due to the non-uniform radiation distribution inside the hohlraum. In this work, the non-uniform radiation properties of both vacuum and gas-filled hohlraums are studied by investigating the angular distribution of the radiation temperature experimentally and numerically. It is found that the non-uniform radiation distribution inside the hohlraum induces the variation of the radiation temperature between different view angles. The simulations show that both the angular distribution of the radiation temperature and the hohlraum radiation distribution can be affected by the electron heat flux. The measured angular distribution of the radiation temperature is more consistent with the simulations when the electron heat flux limiter f e = 0.1 . Comparisons between the experiments and simulations further indicate that the x-ray emission of the blow-off plasma is overestimated in the simulations when it stagnates around the hohlraum axis. The axial position of the laser spot can also be estimated by the angular distribution of the radiation temperature due to their sensitive dependence. The inferred laser spot moves closer to the laser entrance hole in the gas-filled hohlraum than that in the vacuum hohlraum, consisting with the x-ray images taken from the framing camera. The angular distribution of the radiation temperature provides an effective way to investigate the hohlraum radiation properties and introduces more constraint to the numerical modeling of the hohlraum experiments.
Non-Equilibrium Properties from Equilibrium Free Energy Calculations
Pohorille, Andrew; Wilson, Michael A.
2012-01-01
Calculating free energy in computer simulations is of central importance in statistical mechanics of condensed media and its applications to chemistry and biology not only because it is the most comprehensive and informative quantity that characterizes the eqUilibrium state, but also because it often provides an efficient route to access dynamic and kinetic properties of a system. Most of applications of equilibrium free energy calculations to non-equilibrium processes rely on a description in which a molecule or an ion diffuses in the potential of mean force. In general case this description is a simplification, but it might be satisfactorily accurate in many instances of practical interest. This hypothesis has been tested in the example of the electrodiffusion equation . Conductance of model ion channels has been calculated directly through counting the number of ion crossing events observed during long molecular dynamics simulations and has been compared with the conductance obtained from solving the generalized Nernst-Plank equation. It has been shown that under relatively modest conditions the agreement between these two approaches is excellent, thus demonstrating the assumptions underlying the diffusion equation are fulfilled. Under these conditions the electrodiffusion equation provides an efficient approach to calculating the full voltage-current dependence routinely measured in electrophysiological experiments.
Equations for calculating the properties of dissociated steam
Aminov, R. Z.; Gudym, A. A.
2017-08-01
The equations of state for dissociated steam have been developed in the temperature and pressure ranges of 1250-2300 K and 0.01-10.00 MPa for calculating thermodynamic processes in thermal power units operating on high-temperature steam. These equations are based on the property tables for dissociated steam derived at a reference temperature of 0 K. It is assumed that the initial substance is steam, the dissociation of which—in accordance with the most likely chemical reactions—results in formation of molecules of hydrogen, oxygen, steam, hydroxyl, and atoms of oxygen and hydrogen. Differential thermodynamic correlations, considering a change in the chemical potential and the composition of the mixture, during the steam dissociation are used. A reference temperature of 0.01°C used in the calculation of parameters of nondissociated steam has been adopted to predict processes in thermal power units without matching the reference temperatures and to account for transformation of dissociated steam into its usual form for which there is the international system of equations with the water triple point of 0.01°C taken as the reference. In the investigated region, the deviation of dissociated steam properties from those of nondissociated steam, which increases with decreasing the pressure or increasing the temperature, was determined. For a pressure of 0.02 MPa and a temperature of 2200 K, these deviations are 512 kJ/kg for the enthalpy, 0.2574 kJ/(kg K) for the entropy, and 3.431 kJ/(kg K) for the heat capacity at constant pressure. The maximum deviation of the dissociated steam properties calculated by the developed equations from the handbook values that these equations are based on does not exceed 0.03-0.05%.
Radiation processing and functional properties of soybean (Glycine max)
Energy Technology Data Exchange (ETDEWEB)
Pednekar, Mrinal, E-mail: mrinal1854@yahoo.co.i [Food Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, Maharashtra (India); Das, Amit K. [Department of Food Engineering, CFTRI, Mysore 570020, Karnataka (India); Rajalakshmi, V; Sharma, Arun [Food Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, Maharashtra (India)
2010-04-15
Effect of radiation processing (10, 20 and 30 kGy) on soybean for better utilization was studied. Radiation processing reduced the cooking time of soybean and increased the oil absorption capacity of soy flour without affecting its proximate composition. Irradiation improved the functional properties like solubility, emulsification activity and foam stability of soybean protein isolate. The value addition effect of radiation processing has been discussed for the products (soy milk, tofu and tofu fortified patties) prepared from soybean.
Radiation processing and functional properties of soybean ( Glycine max)
Pednekar, Mrinal; Das, Amit K.; Rajalakshmi, V.; Sharma, Arun
2010-04-01
Effect of radiation processing (10, 20 and 30 kGy) on soybean for better utilization was studied. Radiation processing reduced the cooking time of soybean and increased the oil absorption capacity of soy flour without affecting its proximate composition. Irradiation improved the functional properties like solubility, emulsification activity and foam stability of soybean protein isolate. The value addition effect of radiation processing has been discussed for the products (soy milk, tofu and tofu fortified patties) prepared from soybean.
Long fiber polymer composite property calculation in injection molding simulation
Jin, Xiaoshi; Wang, Jin; Han, Sejin
2013-05-01
Long fiber filled polymer composite materials have attracted a great attention and usage in recent years. However, the injection and compression molded long fiber composite materials possess complex microstructures that include spatial variations in fiber orientation and length. This paper presents the recent implemented anisotropic rotary diffusion - reduced strain closure (ARD-RSC) model for predicting fiber orientation distribution[1] and a newly developed fiber breakage model[2] for predicting fiber length distribution in injection and compression molding simulation, and Eshelby-Mori-Tanaka model[3,4] with fiber-matrix de-bonding model[5] have been implemented to calculate the long fiber composite property distribution with predicted fiber orientation and fiber length distributions. A validation study on fiber orientation, fiber breakage and mechanical property distributions are given with injection molding process simulation.
Investigating Radiation Shielding Properties of Different Mineral Origin Heavyweight Concretes
Basyigit, Celalettin; Uysal, Volkan; Kilinçarslan, Şemsettin; Mavi, Betül; Günoǧlu, Kadir; Akkurt, Iskender; Akkaş, Ayşe
2011-12-01
The radiation although has hazardous effects for human health, developing technologies bring lots of usage fields to radiation like in medicine and nuclear power station buildings. In this case protecting from undesirable radiation is a necessity for human health. Heavyweight concrete is one of the most important materials used in where radiation should be shielded, like those areas. In this study, used heavyweight aggregates of different mineral origin (Limonite, Siderite), in order to prepare different series in concrete mixtures and investigated radiation shielding properties. The experimental results on measuring the radiation shielding, the heavyweight concrete prepared with heavyweight aggregates of different mineral origin show that, are useful radiation absorbents when they used in concrete mixtures.
Calculation of the extreme ultraviolet radiation of the earth’s plasmasphere
Institute of Scientific and Technical Information of China (English)
FOK; Mei-Ching
2010-01-01
The dynamic global core plasma model(DGCPM) is used in this paper to calculate the He+ density distribution of the Earth’s plasmasphere and to investigate the configurations and 30.4 nm radiation properties of the plasmasphere.Validation comparisons between the simulation results and IMAGE mission observations show:That the equatorial structure of the plasmapause is mainly located near 5.5 RE and the typical scale of plasmasphere shrinking or expansion within 10 min is approximately 0.1 RE;that the plasmaspheric shoulders are formed and rotate noon-ward from the dawn sector under the conditions of strong southward turning of the interplanetary magnetic field(IMF);that the plasmaspheric plumes will rotate dawn-ward from the night sector and become narrow for the southward turning of the IMF.The simulated images from the lunar orbit show that the plasmasphere locating within the geocentric distance of 5.5 RE corresponds to field of view(FOV) of 10.7°×10.7° for the moon-based EUV imager,and that the 30.4 nm radiation intensity of the plasmasphere is 0.1-11.4 R.The plasmaspheric shoulders and plumes locating toward the moon-side are for the first time simulated with typical scale level of 0.1 RE from the side view of the moon.These simulated results provide an important theoretical basis for the lunar-based EUV camera design.
Energy Technology Data Exchange (ETDEWEB)
Sin, M. W.; Kim, M. H. [Kyunghee Univ., Yongin (Korea, Republic of)
2002-10-01
To calculate total dose effect on semi-conductor devices in satellite for a period of space mission effectively, two approximate calculation models for a comic radiation shielding were proposed. They are a sectoring method and a chord-length distribution method. When an approximate method was applied in this study, complex structure of satellite was described into multiple 1-dimensional slabs, structural materials were converted to reference material(aluminum), and the pre-calculated dose-depth conversion function was introduced to simplify the calculation process. Verification calculation was performed for orbit location and structure geometry of KITSAT-1 and compared with detailed 3-dimensional calculation results and experimental values. The calculation results from approximate method were estimated conservatively with acceptable error. However, results for satellite mission simulation were underestimated in total dose rate compared with experimental values.
Energy Technology Data Exchange (ETDEWEB)
Valero, Francisco P. J. [Atmospheric Research Laboratory, Center for Atmospheric Sciences, Scripps Institution of Oceanography, University of California, San Diego, California (United States); Bush, Brett C. [Atmospheric Research Laboratory, Center for Atmospheric Sciences, Scripps Institution of Oceanography, University of California, San Diego, California (United States)
1999-11-27
Modeled and measured surface insolations are compared with the purpose of evaluating the ability of a radiative transfer model to predict the amount of solar radiation reaching the surface under clear-sky conditions. Model uncertainties are estimated by performing sensitivity studies for variations in aerosol optical depth, aerosol optical properties, water vapor profiles, ozone content, solar irradiance at the top of the atmosphere, and surface albedo. In this fashion, a range of possible calculated values is determined and compared to observations. Experimental errors are evaluated by comparison with independent, simultaneous measurements performed using two World Radiation Reference instrument arrays that were operational for a limited period during SUCCESS. Assuming a mineral aerosol, it is found that there is agreement between calculated and measured fluxes, with differences approximately equal to and within one standard deviation. Such agreement improves further if a layer containing a small amount of carbonaceous aerosol is added. The presence of carbonaceous aerosols is likely because occasional biomass burning activities took place during SUCCESS in the area around the experimental site (the clouds and radiation test bed operated by the Department of Energy in Oklahoma). (c) 2000 American Geophysical Union.
Quantum calculation of the Vavilov-Cherenkov radiation by twisted electrons
Ivanov, I. P.; Serbo, V. G.; Zaytsev, V. A.
2016-05-01
We present a detailed quantum electrodynamical description of Vavilov-Cherenkov radiation emitted by a relativistic twisted electron in the transparent medium. Simple expressions for the spectral and spectral-angular distributions as well as for the polarization properties of the emitted radiation are obtained. Unlike the plane-wave case, the twisted electron produces radiation within the annular angular region, with enhancement towards its boundaries. Additionally, the emitted photons can have linear polarization not only in the scattering plane but also in the orthogonal direction. We find that the Vavilov-Cherenkov radiation emitted by an electron in a superposition of two vortex states exhibits a strong azimuthal asymmetry. Thus, the Vavilov-Cherenkov radiation offers itself as a convenient diagnostic tool of such electrons and complements the traditional microscopic imaging.
Quantum calculation of the Vavilov-Cherenkov radiation by twisted electrons
Ivanov, I P; Zaytsev, V A
2016-01-01
We present the detailed quantum electrodynamical description of Vavilov-Cherenkov radiation emitted by a relativistic twisted electron in the transparent medium. Simple expressions for the spectral and spectral-angular distributions as well as for the polarization properties of the emitted radiation are obtained. Unlike the plane-wave case, the twisted electron produces radiation within the annular angular region, with enhancement towards its boundaries. Additionally, the emitted photons can have linear polarization not only in the scattering plane but also in the orthogonal direction. We find that the Vavilov-Cherenkov radiation emitted by an electron in a superposition of two vortex states exhibits a strong azimuthal asymmetry. Thus, the Vavilov-Cherenkov radiation offers itself as a convenient diagnostic tool of such electrons and complements the traditional microscopic imaging.
Radiation therapy calculations using an on-demand virtual cluster via cloud computing
Keyes, Roy W; Arnold, Dorian; Luan, Shuang
2010-01-01
Computer hardware costs are the limiting factor in producing highly accurate radiation dose calculations on convenient time scales. Because of this, large-scale, full Monte Carlo simulations and other resource intensive algorithms are often considered infeasible for clinical settings. The emerging cloud computing paradigm promises to fundamentally alter the economics of such calculations by providing relatively cheap, on-demand, pay-as-you-go computing resources over the Internet. We believe that cloud computing will usher in a new era, in which very large scale calculations will be routinely performed by clinics and researchers using cloud-based resources. In this research, several proof-of-concept radiation therapy calculations were successfully performed on a cloud-based virtual Monte Carlo cluster. Performance evaluations were made of a distributed processing framework developed specifically for this project. The expected 1/n performance was observed with some caveats. The economics of cloud-based virtual...
Calculation of Radiative Corrections to E1 matrix elements in the Neutral Alkalis
Energy Technology Data Exchange (ETDEWEB)
Sapirstein, J; Cheng, K T
2004-09-28
Radiative corrections to E1 matrix elements for ns-np transitions in the alkali metal atoms lithium through francium are evaluated. They are found to be small for the lighter alkalis but significantly larger for the heavier alkalis, and in the case of cesium much larger than the experimental accuracy. The relation of the matrix element calculation to a recent decay rate calculation for hydrogenic ions is discussed, and application of the method to parity nonconservation in cesium is described.
Monte Carlo calculations of the properties of solid nitromethane
Rice, Betsy M.; Trevino, Samuel F.
1991-09-01
Pairwise additive potential energy functions for H-O, H-H, and O-O intermolecular interactions are presented; methods by which these functions were developed are discussed, and preliminary Monte Carlo calculations of the crystal lattice parameters using these functions are presented. The results indicate that these potential energy functions correctly reproduce the lattice parameters measured by neutron diffraction at 4.2 K, ambient pressure, and at pressures below 1.0 GPa, room temperature. It is our intention in this and future work to obtain sufficient information concerning the intermolecular interactions between molecules of nitromethane (CH3NO2) in order to produce, via computer simulation, a reliable equation of state and other related properties in the condensed phase. For this purpose, substantial experimental investigations have been performed in the past on several properties of the crystal. For the present study, the most important of these are the determination of the crystal structure at ambient pressure, from 4.2 K to 228 K (Trevino, Prince, and Hubbard 1980) and neutron spectroscopic determination of the rotational properties of the methyl group (Trevino and Rymes 1980; Alefeld et al. 1982; Cavagnat et al. 1985).
Numerical calculation of the plume infrared radiation of a long-endurance UAV
Huang, Zhang-bin; Li, Xiao-xia; Feng, Yun-song
2016-11-01
Plume is the main infrared source of a long-endurance UAV, and its infrared radiation numerical calculation is very important for calculating the infrared characteristcs of the whole UAV. This paper built the geometrical model of the flow field structure of UAV plume by analyzing the characteristcs of the flow structure. And, The temperaturre field distribution of the UAV plume was calculated based on the eddy current propagation theory. And then, spectral infrared radiation characteristics of the UAV plume at 2-5μm were obtained by the single band C-G approximation method. The results show that the temperature in the core area of the UAV plume is higher , and the infared radiation characteristics are stable and obvious. The infrared radiation energy of the plume mainly ditributed at the infrared wavelength of 2.7μm and 4.5μm,which is in accordance with the actual situation. The results maybe contribute to the further study of the infrared radiation characteristics of the long-endurance UAV.
Thermodynamic properties of the blackbody radiation: A Kaniadakis approach
Lourek, Imene; Tribeche, Mouloud
2017-02-01
The thermodynamic properties of the blackbody radiation are revisited, for the first time, within the theoretical framework of the κ-statistics introduced by Kaniadakis. Using the κ-counterpart of the Bose-Einstein distribution, generalized expressions for the free energy, the entropy, the specific heat, and the pressure are obtained. All quantities are shown to recover their standard expressions in the limit κ → 0. The reexamination of the thermodynamic properties of the blackbody radiation shows that it emits more energy with an increase of the value of | κ | in comparison with the standard Planck radiation law. Moreover, the effects of the deformed Kaniadakis statistics are shown to be more appreciable for high temperatures. Our results could be used as a theoretical support for experimental studies implying blackbody radiation such as the study of microwave background radiation.
Model-Independent Calculation of Radiative Neutron Capture on Lithium-7
Rupak, Gautam; Higa, Renato
2011-01-01
The radiative neutron capture on lithium-7 is calculated model independently using a low-energy halo effective field theory. The cross section is expressed in terms of scattering parameters directly related to the S-matrix elements. It depends on the poorly known p-wave effective range parameter r(1
Numerical Tests and Properties of Waves in Radiating Fluids
Energy Technology Data Exchange (ETDEWEB)
Johnson, B M; Klein, R I
2009-09-03
We discuss the properties of an analytical solution for waves in radiating fluids, with a view towards its implementation as a quantitative test of radiation hydrodynamics codes. A homogeneous radiating fluid in local thermodynamic equilibrium is periodically driven at the boundary of a one-dimensional domain, and the solution describes the propagation of the waves thus excited. Two modes are excited for a given driving frequency, generally referred to as a radiative acoustic wave and a radiative diffusion wave. While the analytical solution is well known, several features are highlighted here that require care during its numerical implementation. We compare the solution in a wide range of parameter space to a numerical integration with a Lagrangian radiation hydrodynamics code. Our most significant observation is that flux-limited diffusion does not preserve causality for waves on a homogeneous background.
Calculation of nonlinear optical properties of molecular clusters
Energy Technology Data Exchange (ETDEWEB)
Yartsev, V. M.; Marcano O, A. [Instituto Venezolano de Investigaciones Cientificas, Caracas (Venezuela)
2001-03-01
Effects of electronic correlation and electron-intramolecular vibration coupling on the non-linear optical properties are studied. The Hubbard Hamiltonian is used for explicit treatment of electronic correlation in molecular dimmer. The static polarizability and the static second hyper polarizability {gamma} are calculated and their dependences on the model parameters are analyzed. The role of interaction between ion-radical complexes is considered within the model of two parallel dimers. [Spanish] Se estudian los efectos de correlacion y el acoplamiento del electron con las vibraciones moleculares sobre las propiedades opticas no lineales de agregados moleculares. Se utiliza un hamiltoniano de tipo Hubbard para el tratamiento explicito de la correlacion electronica en un dimero molecular. Se calculan la polarizabilidad estatica {alpha} y la hiperpolarizabilidad de segundo orden {gamma} al igual que se analizan sus dependencias de los parametros del modelo. Se estudia ademas el papel de la interaccion entre complejos ino-radical dentro del modelo de dos dimeros paralelos.
Modeling silica aerogel optical performance by determining its radiative properties
Directory of Open Access Journals (Sweden)
Lin Zhao
2016-02-01
Full Text Available Silica aerogel has been known as a promising candidate for high performance transparent insulation material (TIM. Optical transparency is a crucial metric for silica aerogels in many solar related applications. Both scattering and absorption can reduce the amount of light transmitted through an aerogel slab. Due to multiple scattering, the transmittance deviates from the Beer-Lambert law (exponential attenuation. To better understand its optical performance, we decoupled and quantified the extinction contributions of absorption and scattering separately by identifying two sets of radiative properties. The radiative properties are deduced from the measured total transmittance and reflectance spectra (from 250 nm to 2500 nm of synthesized aerogel samples by solving the inverse problem of the 1-D Radiative Transfer Equation (RTE. The obtained radiative properties are found to be independent of the sample geometry and can be considered intrinsic material properties, which originate from the aerogel’s microstructure. This finding allows for these properties to be directly compared between different samples. We also demonstrate that by using the obtained radiative properties, we can model the photon transport in aerogels of arbitrary shapes, where an analytical solution is difficult to obtain.
Chubar, Oleg; Chu, Yong S.; Kaznatcheev, Konstantine; Yan, Hanfei
2011-09-01
Ultra-low emittance third-generation synchrotron radiation (SR) sources, such as NSLS-II and MAX-IV, will offer excellent opportunities for further development of experimental techniques exploiting X-ray coherence. However, even in these new SR sources, the radiation produced by relativistic electrons (in undulators, wigglers and bending magnets) will remain only partially coherent in the X-ray spectral range. "Extraction" of "coherent portion" of the radiation flux and its transport to sample without loss of coherence must be performed by dedicated SR beamlines, optimized for particular types of experiments. Detailed quantitative prediction of partially coherent X-ray beam properties at propagation through optical elements, which is required for the optimization of such beamlines, can only be obtained from accurate and efficient physical-optics based numerical simulations. Examples of such simulations, made for NSLS-II beamlines, using "Synchrotron Radiation Workshop" (SRW) computer code, are presented. Special attention is paid to the numerical analysis of the basic properties of partially coherent undulator radiation beam and its distinctions from the Gaussian beam. Performance characteristics of importance for particular beamlines, such as radiation spot size and flux at sample vs size of secondary source aperture for high-resolution microscopy beamlines, are predicted by the simulations.
Ab initio calculations of yttrium nitride: structural and electronic properties
Energy Technology Data Exchange (ETDEWEB)
Zerroug, S.; Ali Sahraoui, F. [Universite Ferhat Abbas, Laboratoire d' Optoelectronique et Composants, Departement de Physique, Setif (Algeria); Bouarissa, N. [King Khalid University, Department of Physics, Faculty of Science, P.O. Box 9004, Abha (Saudi Arabia)
2009-11-15
Using first principles total energy calculations within the full-potential linearized augmented plane wave method, we have studied the structural and electronic properties of yttrium nitride (YN) in the three phases, namely wurtzite, caesium chloride and rocksalt structures. The calculations are performed at zero and under hydrostatic pressure. In agreement with previous findings, it is found that the favored phase for YN is the rocksalt-like structure. We predict that at zero pressure YN in the rocksalt structure is a semiconductor with an indirect bandgap of 0.8 eV. A phase transition from a rocksalt to a caesium chloride structure is found to occur at {proportional_to}134 GPa. Besides, a transition from an indirect ({gamma}-X) bandgap semiconductor to a direct (X-X) one is predicted at pressure of {proportional_to}84 GPa. For the electron effective mass of rocksalt YN, these are the first results, to our knowledge. The information derived from the present study may be useful for the use of YN as an active layer in electronic devices such as diodes and transistors. (orig.)
The optical properties of equatorial cirrus in the pilot radiation observation experiment
Energy Technology Data Exchange (ETDEWEB)
Platt, C.M.R.; Young, S.A.; Manson, P.; Patterson, G.R. [CSIRO, Victoria (Australia)] [and others
1996-04-01
The development of a sensitive filter radiometer for the Atmospheric Radiation Measurement (ARM) Program has been reported. The aim was to develop a reliable and fast instrument that could be used alongside a lidar to obtain near realtime optical properties of clouds, particularly high ice clouds, as they drifted over an ARM Cloud and Radiation Testbed (CART) site allowing calculation of the radiation divergence in the atmosphere over the site. Obtaining cloud optical properties by the lidar/radiometer, or LIRAD, method was described by Platt et al.; the latter paper also describes a year`s data on mid-latitude cirrus. The optical properties of equatorial cirrus (i.e., cirrus within a few degrees of the equator) have hardly been studied at all. The same is true of tropical cirrus, although a few observations have been reported by Davis and Platt et al.This paper describes obersvations performed on cirrus clouds, analysis methods used, and results.
Surface radiation properties of ThO/sub 2/ and other reactor materials
Energy Technology Data Exchange (ETDEWEB)
Chan, S.H.; Ma, H.H.
1979-12-01
This technical report summarizes the results obtained on surface radiation properties of ThO/sub 2/ and other related reactor materials. Specifically, the present study provides surface radiation properties of three nuclear reactor materials; thorium dioxide, sodium and steel (99 Fe + 1 C). First, based on transmission spectra and Kramers-Kronig analysis, the complex refractive index, which is fundamental to surface radiation property calculations, of ThO/sub 2/ is presented over a wide spectral range. Then depending on the contacting media, three types of the surface are considered. They are the interfaces between ThO/sub 2/ and Sodium, ThO/sub 2/ and Steel (99 Fe + 1 C) as well as ThO/sub 2/ and a gas. For each interface, the spectral interface reflectance from one side of the medium to the other side is evaluated for all wavelengths.
Spectral Radiative Properties of Two-Dimensional Rough Surfaces
Xuan, Yimin; Han, Yuge; Zhou, Yue
2012-12-01
Spectral radiative properties of two-dimensional rough surfaces are important for both academic research and practical applications. Besides material properties, surface structures have impact on the spectral radiative properties of rough surfaces. Based on the finite difference time domain algorithm, this paper studies the spectral energy propagation process on a two-dimensional rough surface and analyzes the effect of different factors such as the surface structure, angle, and polarization state of the incident wave on the spectral radiative properties of the two-dimensional rough surface. To quantitatively investigate the spatial distribution of energy reflected from the rough surface, the concept of the bidirectional reflectance distribution function is introduced. Correlation analysis between the reflectance and different impact factors is conducted to evaluate the influence degree. Comparison between the theoretical and experimental data is given to elucidate the accuracy of the computational code. This study is beneficial to optimizing the surface structures of optoelectronic devices such as solar cells.
A model to calculate solar radiation fluxes on the Martian surface
Directory of Open Access Journals (Sweden)
Vicente-Retortillo Álvaro
2015-01-01
Full Text Available We present a new comprehensive radiative transfer model to study the solar irradiance that reaches the surface of Mars in the spectral range covered by MetSIS, a sensor aboard the Mars MetNet mission that will measure solar irradiance in several bands from the ultraviolet (UV to the near infrared (NIR. The model includes up-to-date wavelength-dependent radiative properties of dust, water ice clouds, and gas molecules. It enables the characterization of the radiative environment in different spectral regions under different scenarios. Comparisons between the model results and MetSIS observations will allow for the characterization of the temporal variability of atmospheric optical depth and dust size distribution, enhancing the scientific return of the mission. The radiative environment at the Martian surface has important implications for the habitability of Mars as well as a strong impact on its atmospheric dynamics and climate.
Dyer, C. S.; Lei, F.; Clucas, S. N.; Smart, D. F.; Shea, M. A.
Solar particle events can give greatly enhanced radiation at aircraft altitudes, but are both difficult to predict and to calculate retrospectively. This enhanced radiation can give significant dose to aircrew and greatly increase the rate of single event effects in avionics. Validation of calculations is required but only very few events have been measured in flight. The CREAM detector on Concorde detected the event of 29 September 1989 and also four periods of enhancement during the events of 19-24 October 1989. Instantaneous rates were enhanced by up to a factor ten compared with quiet-time cosmic rays, while flight-averages were enhanced by up to a factor six. Calculations are described for increases in radiation at aircraft altitudes using solar particle spectra in conjunction with Monte Carlo radiation transport codes. In order to obtain solar particle spectra with sufficient accuracy over the required energy range it is necessary to combine space data with measurements from a wide range of geomagnetically dispersed, ground-level neutron monitors. Such spectra have been obtained for 29 September 1989 and 24 October 1989 and these are used to calculate enhancements that are compared with the data from CREAM on Concorde. The effect of cut-off rigidity suppression by geomagnetic activity is shown to be significant. For the largest event on record on 23 February 1956, there are no space data but there are data from a number of ground-level cosmic-ray detectors. Predictions for all events show very steep dependencies on both latitude and altitude. At high latitude and altitude (17 km) calculated increases with respect to cosmic rays are a factor 70 and 500 respectively for 29 September 1989 and 23 February 1956. The levels of radiation for high latitude, subsonic routes are calculated, using London to Los Angeles as an example, and can exceed 1 mSv, which is significantly higher than for Concorde routes from Europe to New York. The sensitivity of the calculations
Akataş, Nilcan; Yeşilköy, Serhan; Şaylan, Levent
2016-04-01
Determination of surface energy balance over agricultural lands plays a crucial role to better investigation of sustainable agriculture and food security which are related to evapotranspiration. Surface energy balance components that include net shortwave and longwave radiation depend on surface conditions like surface albedo and climate of a region. Surface albedo is ratio between reflected longwave radiation and incoming shortwave radiation. There are many different crops in agriculture ecosystem. Thus, surface energy balance components vary by vegetation surfaces. Net radiation is most important component of surface energy balance which is difference between net shortwave and longwave radiation. These are calculated by commonly used equations and applied to the FAO Penman& Monteith equation using meteorological stations' data located in cities. However, there are differences between urban areas and agricultural ecosystems. This situation causes to the calculation errors. In this research, it is aimed to investigate the changes between estimated and measured surface energy balance components which are estimated by meteorological stations' data in the urban area and measurements from an rural area over winter wheat surface 2014-2015 growing season in Thrace Region located in the Northwestern part of Turkey, Kırklareli city. Keywords: Surface energy balance, winter wheat, FAO Penman-Monteith, Kırklareli/Turkey
Properties of the Third Harmonic of the SASE FEL Radiation
Saldin, E L; Schneidmiller, E
2005-01-01
Recent theoretical and experimental studies have shown that SASE FEL with a planar undulator holds a potential for generation of relatively strong coherent radiation at the third harmonic of the fundamental frequency. Here we present detailed study of the nonlinear harmonic generation in SASE FEL obtained with time-dependent FEL simulation code FAST. Using similarity techniques we present universal dependencies for temporal, spectral, and statistical properties of the third harmonic radiation from SASE FEL.
Energetics and Radiative Properties of Excimer Lasers
1981-01-01
the Asymmetric Stretch Mode of Carbon Dioxide by Hydrogen," Chemical Physics Letters. Vol. 10, p. 498, 1971. Michels, H. H. and H. P. Broida...Letters, 39A, 349 (1972), 21. R. S. Carbone and M. M. Litvak, J. Applied Physics, 39, 2413 (1968). 22. R. S. Mulliken, Journal of Chemical Physics, 52...per- tinent potential energy curves and calculated spectroscopic constants. Further papers in this series deal with photodissociation and
Takahashi, F; Endo, A
2007-01-01
A system utilising radiation transport codes has been developed to derive accurate dose distributions in a human body for radiological accidents. A suitable model is quite essential for a numerical analysis. Therefore, two tools were developed to setup a 'problem-dependent' input file, defining a radiation source and an exposed person to simulate the radiation transport in an accident with the Monte Carlo calculation codes-MCNP and MCNPX. Necessary resources are defined by a dialogue method with a generally used personal computer for both the tools. The tools prepare human body and source models described in the input file format of the employed Monte Carlo codes. The tools were validated for dose assessment in comparison with a past criticality accident and a hypothesized exposure.
A short history of nomograms and tables used for thermal radiation calculations
Stewart, Seán. M.; Johnson, R. Barry
2016-09-01
The theoretical concept of a perfect thermal radiator, the blackbody, was first introduced by the German physicist Gustav Robert Kirchhoff in 1860. By the latter half of the nineteenth century it had become the object of intense theoretical and experimental investigation. While an attempt at trying to theoretically understand the behavior of radiation emitted from a blackbody was undertaken by many eminent physicists of the day, its solution was not found until 1900 when Max Planck put forward his now famous law for thermal radiation. Today, of course, understanding blackbody behavior is vitally important to many fields including infrared systems, illumination, pyrometry, spectroscopy, astronomy, thermal engineering, cryogenics, and meteorology. Mathematically, the form Planck's law takes is rather cumbersome meaning calculations made with it before the advent of modern computers were rather tedious, dramatically slowing the process of computation. Fortunately, during those early days of the twentieth century researchers quickly realized Planck's equation, and the various functions closely related to it, readily lend themselves to being given a graphical, mechanical, or numerically tabulated form for their evaluation. The first of these computational aids to appear were tables. These arose shortly after Planck introduced his equation, were produced in the greatest number, and remained unsurpassed in their level of accuracy compared to all other aids made. It was also not long before nomograms designed to aid thermal radiation calculations appeared. Essentially a printed chart and requiring nothing more than a straightedge to use, nomograms were cheap and extremely easy to use. Facilitating instant answers to a range of quantities relating to thermal radiation, a number were produced and the inventiveness displayed in some was quite remarkable. In this paper we consider the historical development of many of the nomograms and tables developed and used by generations
2015-01-01
An Algorithm to Calculate Phase-Center Offset of Aperture Antennas when Measuring 2-Dimensional Radiation Patterns by Patrick Debroux...Offset of Aperture Antennas when Measuring 2-Dimensional Radiation Patterns Patrick Debroux and Berenice Verdin Survivability/Lethality Analysis... Antennas when Measuring 2-Dimensional Radiation Patterns 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S
Feng, Chi; Li, Dong; Gao, Shan; Daniel, Ketui
2016-11-01
This paper presents a CFD (Computation Fluid Dynamic) simulation and experimental results for the reflected radiation error from turbine vanes when measuring turbine blade's temperature using a pyrometer. In the paper, an accurate reflection model based on discrete irregular surfaces is established. Double contour integral method is used to calculate view factor between the irregular surfaces. Calculated reflected radiation error was found to change with relative position between blades and vanes as temperature distribution of vanes and blades was simulated using CFD. Simulation results indicated that when the vanes suction surface temperature ranged from 860 K to 1060 K and the blades pressure surface average temperature is 805 K, pyrometer measurement error can reach up to 6.35%. Experimental results show that the maximum pyrometer absolute error of three different targets on the blade decreases from 6.52%, 4.15% and 1.35% to 0.89%, 0.82% and 0.69% respectively after error correction.
[Calculation of radiation loads in a space station compartment with a secondary shielding].
Kartashov, D A; Tolochek, R V; Shurshakov, V A; Yarmanova, E N
2013-01-01
Doses from space ionizing radiation were estimated using a model of ISS cosmonaut's quarters (CQ) outfitted with secondary shielding ("Protective shutter" (PS) as part of experiment MATRYOSHKA-R). Protective shutter is a "blanket" of water-containing material with mass thickness of - 6 g/cm2 covering the CQ exterior wall. Calculation was performed specifically for locations of experimental dosimetry assemblies. Agreement of calculations and experimental data reaching accuracy - 15% proves model applicability to estimating protective effectiveness of secondary shielding in the present-day and future space vehicles. This shielding may reduce radiation loading onto crewmembers as an equivalent dose by more than 40% within a broad range of orbit altitudes equally during the solar minimum and maximum.
Bakshi, A K; Chatterjee, S; Palani Selvam, T; Dhabekar, B S
2010-07-01
In the present study, the energy dependence of response of some popular thermoluminescent dosemeters (TLDs) have been investigated such as LiF:Mg,Ti, LiF:Mg,Cu,P and CaSO(4):Dy to synchrotron radiation in the energy range of 10-34 keV. The study utilised experimental, Monte Carlo and analytical methods. The Monte Carlo calculations were based on the EGSnrc and FLUKA codes. The calculated energy response of all the TLDs using the EGSnrc and FLUKA codes shows excellent agreement with each other. The analytically calculated response shows good agreement with the Monte Carlo calculated response in the low-energy region. In the case of CaSO(4):Dy, the Monte Carlo-calculated energy response is smaller by a factor of 3 at all energies in comparison with the experimental response when polytetrafluoroethylene (PTFE) (75 % by wt) is included in the Monte Carlo calculations. When PTFE is ignored in the Monte Carlo calculations, the difference between the calculated and experimental response decreases (both responses are comparable >25 keV). For the LiF-based TLDs, the Monte Carlo-based response shows reasonable agreement with the experimental response.
Applying graphics processor units to Monte Carlo dose calculation in radiation therapy
Directory of Open Access Journals (Sweden)
Bakhtiari M
2010-01-01
Full Text Available We investigate the potential in using of using a graphics processor unit (GPU for Monte-Carlo (MC-based radiation dose calculations. The percent depth dose (PDD of photons in a medium with known absorption and scattering coefficients is computed using a MC simulation running on both a standard CPU and a GPU. We demonstrate that the GPU′s capability for massive parallel processing provides a significant acceleration in the MC calculation, and offers a significant advantage for distributed stochastic simulations on a single computer. Harnessing this potential of GPUs will help in the early adoption of MC for routine planning in a clinical environment.
Independent verification of monitor unit calculation for radiation treatment planning system.
Chen, Li; Chen, Li-Xin; Huang, Shao-Min; Sun, Wen-Zhao; Sun, Hong-Qiang; Deng, Xiao-Wu
2010-02-01
To ensure the accuracy of dose calculation for radiation treatment plans is an important part of quality assurance (QA) procedures for radiotherapy. This study evaluated the Monitor Units (MU) calculation accuracy of a third-party QA software and a 3-dimensional treatment planning system (3D TPS), to investigate the feasibility and reliability of independent verification for radiation treatment planning. Test plans in a homogenous phantom were designed with 3-D TPS, according to the International Atomic Energy Agency (IAEA) Technical Report No. 430, including open, blocked, wedge, and multileaf collimator (MLC) fields. Test plans were delivered and measured in the phantom. The delivered doses were input to the QA software and the independent calculated MUs were compared with delivery. All test plans were verified with independent calculation and phantom measurements separately, and the differences of the two kinds of verification were then compared. The deviation of the independent calculation to the measurements was (0.1 +/- 0.9)%, the biggest difference fell onto the plans that used block and wedge fields (2.0%). The mean MU difference between the TPS and the QA software was (0.6 +/- 1.0)%, ranging from -0.8% to 2.8%. The deviation in dose of the TPS calculation compared to the measurements was (-0.2 +/- 1.7)%, ranging from -3.9% to 2.9%. MU accuracy of the third-party QA software is clinically acceptable. Similar results were achieved with the independent calculations and the phantom measurements for all test plans. The tested independent calculation software can be used as an efficient tool for TPS plan verification.
The Effects of Line-Wing Cutoff in LBL Integration on Radiation Calculations
Institute of Scientific and Technical Information of China (English)
ZHANG Hua; SHI Guangyu; LIU Yi
2008-01-01
There are three basic methods in radiative transfer calculations, i.e., line-by-line (LBL) integration, correlated k-distribution method, and band model. The LBL integration is the most accurate of all, in which, there are two quadrature algorithms named in this paper as integration by lines and by sampling "points when calculating atmospheric transmittance in the considered wavenumber region. Because the LBL integration is the most expensive of all, it is necessary and important to save calculation time but increase calculation speed when it is put into use in the daily operation in atmospheric remote sensing and atmospheric sounding. A simplified LBL method is given in this paper on the basis of integration by lines, which increases computational speed greatly with keeping the same accuracy. Then, we discuss the effects of different cutoff schemes on atmospheric absorption coefficient, transmittance, and cooling rate under both of accurate and simplified LBL methods in detail. There are four cutoff schemes described in this paper, i.e., CUTOFFs 1, 2, 3, and 4. It is shown by this numerical study that the way to cut off spectral line-wing has a great effect on the accuracy and speed of radiative calculations. The relative errors of the calculated absorption coefficients for CUTOFF 2 are the largest under different pressures, while for CUTOFF 1, they are less than 2% at most of sampling points and for CUTOFFs 3 or 4, they are ahnost less than 5% in the calculated spectral region, however, the calculation time is reduced greatly. We find in this study that the transmittance in the lower atmosphere is not sensitive to different LBL methods and different cutoff schemes. Whereas for the higher atmosphere, the differences of transmittance results between CUTOFF 2 and each of other three cutoff schemes are the biggest of all no matter for the accurate LBL or for the simplified LBL integrations. By comparison, the best and optimized cutoff scheme is given in this paper
Institute of Scientific and Technical Information of China (English)
ZHANG Wanxi; SUN Jiazhen
1987-01-01
In this paper, calculating the molecular internal rotating steric factor of polymers by the radiation crosslinking method is studied and a relationship between the molecular internal rotating steric factor (σ) and crosslinking parameter β is established[1] by taking account of the effect of polymer chain flexibility on β value. σ value of polymer obtained by this method is in agreement with that given with other method.
Spataru, Catalin D.; Ismail-Beigi, Sohrab; Capaz, Rodrigo B.; Louie, Steven G.
2005-01-01
We present theoretical analysis and first-principles calculation of the radiative lifetime of excitons in semiconducting carbon nanotubes. An intrinsic lifetime of the order of 10 ps is computed for the lowest optically active bright excitons. The intrinsic lifetime is however a rapid increasing function of the exciton momentum. Moreover, the electronic structure of the nanotubes dictates the existence of dark excitons nearby in energy to each bright exciton. Both effects strongly influence m...
FlexyDos3D: a deformable anthropomorphic 3D radiation dosimeter: radiation properties
DEFF Research Database (Denmark)
De Deene, Yves; Skyt, Peter Sandegaard; Hill, Robin
2015-01-01
Three dimensional radiation dosimetry has received growing interest with the implementation of highly conformal radiotherapy treatments. The radiotherapy community faces new challenges with the commissioning of image guided and image gated radiotherapy treatments (IGRT) and deformable image...... and oxygen concentration has also been investigated. The radiophysical properties of this new dosimeter are discussed including stability, spatial integrity, temperature dependence of the dosimeter during radiation, readout and storage, dose rate dependence and tissue equivalence....
Radiation Transfer Calculations and Assessment of Global Warming by CO2
Directory of Open Access Journals (Sweden)
Hermann Harde
2017-01-01
Full Text Available We present detailed line-by-line radiation transfer calculations, which were performed under different atmospheric conditions for the most important greenhouse gases water vapor, carbon dioxide, methane, and ozone. Particularly cloud effects, surface temperature variations, and humidity changes as well as molecular lineshape effects are investigated to examine their specific influence on some basic climatologic parameters like the radiative forcing, the long wave absorptivity, and back-radiation as a function of an increasing CO2 concentration in the atmosphere. These calculations are used to assess the CO2 global warming by means of an advanced two-layer climate model and to disclose some larger discrepancies in calculating the climate sensitivity. Including solar and cloud effects as well as all relevant feedback processes our simulations give an equilibrium climate sensitivity of CS = 0.7°C (temperature increase at doubled CO2 and a solar sensitivity of SS = 0.17°C (at 0.1% increase of the total solar irradiance. Then CO2 contributes 40% and the Sun 60% to global warming over the last century.
Voxel2MCNP: software for handling voxel models for Monte Carlo radiation transport calculations.
Hegenbart, Lars; Pölz, Stefan; Benzler, Andreas; Urban, Manfred
2012-02-01
Voxel2MCNP is a program that sets up radiation protection scenarios with voxel models and generates corresponding input files for the Monte Carlo code MCNPX. Its technology is based on object-oriented programming, and the development is platform-independent. It has a user-friendly graphical interface including a two- and three-dimensional viewer. A row of equipment models is implemented in the program. Various voxel model file formats are supported. Applications include calculation of counting efficiency of in vivo measurement scenarios and calculation of dose coefficients for internal and external radiation scenarios. Moreover, anthropometric parameters of voxel models, for instance chest wall thickness, can be determined. Voxel2MCNP offers several methods for voxel model manipulations including image registration techniques. The authors demonstrate the validity of the program results and provide references for previous successful implementations. The authors illustrate the reliability of calculated dose conversion factors and specific absorbed fractions. Voxel2MCNP is used on a regular basis to generate virtual radiation protection scenarios at Karlsruhe Institute of Technology while further improvements and developments are ongoing.
Theory and measurement of emittance properties for radiation thermometry applications.
Dewitt, D. P.; Hernicz, R. S.
1972-01-01
Some basic concepts of radiation physics are briefly reviewed to provide an introduction to the radiative properties - including emittance, reflectance, absorptance, and transmittance - their definitions, interrelations, theory and methods of measurement. Analyzed data showing typical characteristics of temperature and wavelength dependence, surface effects and environmental influences on the radiation properties of selected classes of materials are presented. Emphasis is placed on those emittance properties of particular interest to conventional radiation thermometry applications, but sufficient generality on all properties is presented to be useful for new or unusual techniques where a more detailed understanding of the behavior of materials is desirable. Data sources are identified to assist the reader in locating property information. It is the intention of the paper to give the reader a background to become more fully aware of the pitfalls, limitations, but of course, advantages in the use of data from the literature. The paper is written in the form of an abbreviated review fully documenting the more important topics and concepts which can only be treated briefly.
Impact of morphology on the radiative properties of fractal soot aggregates
Doner, Nimeti; Liu, Fengshan
2017-01-01
The impact of morphology on the radiative properties of fractal soot aggregates was investigated using the discrete dipole approximation (DDA). The optical properties of four different types of aggregates of freshly emitted soot with a fractal dimension Df=1.65 and a fractal pre-factor kf=1.76 were calculated. The four types of aggregates investigated are formed by uniform primary particles in point-touch, by uniform but overlapping primary particles, by uniform but enlarged primary particles in point-touch, and formed by point-touch and polydisperse primary particles. The radiative properties of aggregates consisting of N=20, 56 and 103 primary particles were numerically evaluated for a given refractive index at 0.532 and 1.064 μm. The radiative properties of soot aggregates vary strongly with the volume equivalent radius aeff and wavelength. The accuracy of DDA was evaluated in the first and fourth cases against the generalized multi-sphere Mie (GMM) solution in terms of the vertical-vertical differential scattering cross section (Cvv). The model predicted the average relative deviations from the base case to be within 15-25% for Cvv, depending on the number of particles for the aggregate. The scattering cross sections are only slightly affected by the overlapping but more significantly influenced by primary particle polydispersity. It was also found that the enlargement of primary particles by 20% has a strong effect on soot aggregate radiative properties.
Energy Technology Data Exchange (ETDEWEB)
Serikov, A.; Fischer, U.; Grosse, D.; Leichtle, D.; Majerle, M., E-mail: arkady.serikov@kit.edu [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany)
2011-07-01
The Monte Carlo (MC) method is the most suitable computational technique of radiation transport for shielding applications in fusion neutronics. This paper is intended for sharing the results of long term experience of the fusion neutronics group at Karlsruhe Institute of Technology (KIT) in radiation shielding calculations with the MCNP5 code for the ITER fusion reactor with emphasizing on the use of several ITER project-driven computer programs developed at KIT. Two of them, McCad and R2S, seem to be the most useful in radiation shielding analyses. The McCad computer graphical tool allows to perform automatic conversion of the MCNP models from the underlying CAD (CATIA) data files, while the R2S activation interface couples the MCNP radiation transport with the FISPACT activation allowing to estimate nuclear responses such as dose rate and nuclear heating after the ITER reactor shutdown. The cell-based R2S scheme was applied in shutdown photon dose analysis for the designing of the In-Vessel Viewing System (IVVS) and the Glow Discharge Cleaning (GDC) unit in ITER. Newly developed at KIT mesh-based R2S feature was successfully tested on the shutdown dose rate calculations for the upper port in the Neutral Beam (NB) cell of ITER. The merits of McCad graphical program were broadly acknowledged by the neutronic analysts and its continuous improvement at KIT has introduced its stable and more convenient run with its Graphical User Interface. Detailed 3D ITER neutronic modeling with the MCNP Monte Carlo method requires a lot of computation resources, inevitably leading to parallel calculations on clusters. Performance assessments of the MCNP5 parallel runs on the JUROPA/HPC-FF supercomputer cluster permitted to find the optimal number of processors for ITER-type runs. (author)
Monte Carlo calculation model for heat radiation of inclined cylindrical flames and its application
Chang, Zhangyu; Ji, Jingwei; Huang, Yuankai; Wang, Zhiyi; Li, Qingjie
2017-02-01
Based on Monte Carlo method, a calculation model and its C++ calculating program for radiant heat transfer from an inclined cylindrical flame are proposed. In this model, the total radiation energy of the inclined cylindrical flame is distributed equally among a certain number of energy beams, which are emitted randomly from the flame surface. The incident heat flux on a surface is calculated by counting the number of energy beams which could reach the surface. The paper mainly studies the geometrical evaluation criterion for validity of energy beams emitted by inclined cylindrical flames and received by other surfaces. Compared to Mudan's formula results for a straight cylinder or a cylinder with 30° tilt angle, the calculated view factors range from 0.0043 to 0.2742 and the predicted view factors agree well with Mudan's results. The changing trend and values of incident heat fluxes computed by the model is consistent with experimental data measured by Rangwala et al. As a case study, incident heat fluxes on a gasoline tank, both the side and the top surface are calculated by the model. The heat radiation is from an inclined cylindrical flame generated by another 1000 m3 gasoline tank 4.6 m away from it. The cone angle of the flame to the adjacent oil tank is 45° and the polar angle is 0°. The top surface and the side surface of the tank are divided into 960 and 5760 grids during the calculation, respectively. The maximum incident heat flux on the side surface is 39.64 and 51.31 kW/m2 on the top surface. Distributions of the incident heat flux on the surface of the oil tank and on the ground around the fire tank are obtained, too.
Calculation of residence times and radiation doses using the standard PC software Excel.
Herzog, H; Zilken, H; Niederbremer, A; Friedrich, W; Müller-Gärtner, H W
1997-12-01
We developed a program which aims to facilitate the calculation of radiation doses to single organs and the whole body. IMEDOSE uses Excel to include calculations, graphical displays, and interactions with the user in a single general-purpose PC software tool. To start the procedure the input data are copied into a spreadsheet. They must represent percentage uptake values of several organs derived from measurements in animals or humans. To extrapolate these data up to seven half-lives of the radionuclide, fitting to one or two exponentional functions is included and can be checked by the user. By means of the approximate time-activity information the cumulated activity or residence times are calculated. Finally these data are combined with the absorbed fraction doses (S-values) given by MIRD pamphlet No. 11 to yield radiation doses, the effective dose equivalent and the effective dose. These results are presented in a final table. Interactions are realized with push-buttons and drop-down menus. Calculations use the Visual Basic tool of Excel. In order to test our program, biodistribution data of fluorine-18 fluorodeoxyglucose were taken from the literature (Meija et al., J Nucl Med 1991; 32:699-706). For a 70-kg adult the resulting radiation doses of all target organs listed in MIRD 11 were different from the ICRP 53 values by 1%+/-18% on the average. When the residence times were introduced into MIRDOSE3 (Stabin, J Nucl Med 1996; 37:538-546) the mean difference between our results and those of MIRDOSE3 was -3%+/-6%. Both outcomes indicate the validity of the present approach.
Plante, I.; Cucinotta, F. A.
2010-01-01
INTRODUCTION: The radiation track structure is of crucial importance to understand radiation damage to molecules and subsequent biological effects. Of a particular importance in radiobiology is the induction of double-strand breaks (DSBs) by ionizing radiation, which are caused by clusters of lesions in DNA, and oxidative damage to cellular constituents leading to aberrant signaling cascades. DSB can be visualized within cell nuclei with gamma-H2AX experiments. MATERIAL AND METHODS: In DSB induction models, the DSB probability is usually calculated by the local dose obtained from a radial dose profile of HZE tracks. In this work, the local dose imparted by HZE ions is calculated directly from the 3D Monte-Carlo simulation code RITRACKS. A cubic volume of 5 micron edge (Figure 1) is irradiated by a (Fe26+)-56 ion of 1 GeV/amu (LET approx.150 keV/micron) and by a fluence of 450 H+ ions, 300 MeV/amu (LET approx. 0.3 keV/micron). In both cases, the dose deposited in the volume is approx.1 Gy. The dose is then calculated into each 3D pixels (voxels) of 20 nm edge and visualized in 3D. RESULTS AND DISCUSSION: The dose is deposited uniformly in the volume by the H+ ions. The voxels which receive a high dose (orange) corresponds to electron track ends. The dose is deposited differently by the 56Fe26+ ion. Very high dose (red) is deposited in voxels with direct ion traversal. Voxels with electron track ends (orange) are also found distributed around the path of the track. In both cases, the appearance of the dose distribution looks very similar to DSBs seen in gammaH2AX experiments, particularly when the visualization threshold is applied. CONCLUSION: The refinement of the dose calculation to the nanometer scale has revealed important differences in the energy deposition between high- and low-LET ions. Voxels of very high dose are only found in the path of high-LET ions. Interestingly, experiments have shown that DSB induced by high-LET radiation are more difficult to
Engel-Vosko GGA calculations of the structural, electronic and optical properties of LiYO2
Muhammad, Nisar; Khan, Afzal; Haidar Khan, Shah; Sajjaj Siraj, Muhammad; Shah, Syed Sarmad Ali; Murtaza, Ghulam
2017-09-01
Structural, electronic and optical properties of lithium yttrium oxide (LiYO2) are investigated using density functional theory (DFT). These calculations are based on full potential linearized augmented plane wave (FP-LAPW) method implemented by WIEN2k. The generalized gradient approximation (GGA) is used as an exchange correlation potential with Perdew-Burk-Ernzerhof (PBE) and Engel-Vosko (EV) as exchange correlation functional. The structural properties are calculated with PBE-GGA as it gives the equilibrium lattice constants very close to the experimental values. While, the band structure and optical properties are calculated with EV-GGA obtain much closer results to their experimental values. Our calculations confirm LiYO2 as large indirect band gap semiconductor having band gap of 5.23 eV exhibiting the characteristics of ultrawide band gap materials showing the properties like higher critical breakdown field, higher temperature operation and higher radiation tolerance. In this article, we report the density of states (DOS) in terms of contribution from s, p, and d-states of the constituent atoms, the band structure, the electronic structure, and the frequency-dependent optical properties of LiYO2. The optical properties presented in this article reveal LiYO2 a suitable candidate for the field of optoelectronic and optical devices.
Radiation Damage Study on the Electrical Properties of Si Diodes
Pascoalino, Kelly C. S.; Gonçalves, Josemary A. C.; Tobias, Carmen C. B.
2011-08-01
The aim of this work was to study the radiation damage effects on the electrical properties of Float Zone (FZ) and Magnetic Czochralski (MCz) diodes. The effects were evaluated by measuring the reverse current and capacitance of these devices as a function of the reverse voltage. The irradiation was performed in the Radiation Technology Center (CTR) at IPEN-CNEN/SP using a 60Co irradiator (Gammacell 220-Nordion) with a dose rate of about 2 kGy/h. Samples were irradiated at room temperature in five steps up to an accumulated dose of 603 kGy.
Kartashov, D A; Shurshakov, V A
2012-01-01
The article presents a new procedure of calculating the shielding functions for irregular objects formed from a set of nonintersecting (adjacent) triangles covering completely the surface of each object. Calculated and experimentally derived distributions of space ionizing radiation doses in the spherical tissue-equivalent phantom (experiment MATRYOSHKA-R) inside the International space station were in good agreement in the mass of phantom depths with allowance for measurement error (-10%). The procedure can be applied in modeling radiation loads on cosmonauts, calculating effectiveness of secondary protection in spacecraft, and design review of radiation protection for future space exploration missions.
Relativistic Band Calculation and the Optical Properties of Gold
DEFF Research Database (Denmark)
Christensen, N Egede; Seraphin, B. O.
1971-01-01
The energy band structure of gold is calculated by the relativistic augmented-plane-wave (RAPW) method. A nonrelativistic calculation is also presented, and a comparison between this and the RAPW results demonstrates that the shifts and splittings due to relativistic effects are of the same order....... It is shown that the photoemission results are extremely well described in terms of a model assuming all transitions to be direct whereas a nondirect model fails. The ε2 profile calculated in a crude model assuming constant matrix elements matches well the corresponding experimental results. The calculated...... and comparison to the observed temperature shifts of the elements of structure in the experimental ε2 function. Such structure may originate in extended rather than localized regions of k→ space. In contrast, critical-point transitions show up clearly in modulated reflectance spectra, and all elements...
Robertson, Scott
2014-11-01
Analog gravity experiments make feasible the realization of black hole space-times in a laboratory setting and the observational verification of Hawking radiation. Since such analog systems are typically dominated by dispersion, efficient techniques for calculating the predicted Hawking spectrum in the presence of strong dispersion are required. In the preceding paper, an integral method in Fourier space is proposed for stationary 1+1-dimensional backgrounds which are asymptotically symmetric. Here, this method is generalized to backgrounds which are different in the asymptotic regions to the left and right of the scattering region.
Robertson, Scott; Leonhardt, Ulf
2014-11-01
Hawking radiation has become experimentally testable thanks to the many analog systems which mimic the effects of the event horizon on wave propagation. These systems are typically dominated by dispersion and give rise to a numerically soluble and stable ordinary differential equation only if the rest-frame dispersion relation Ω^{2}(k) is a polynomial of relatively low degree. Here we present a new method for the calculation of wave scattering in a one-dimensional medium of arbitrary dispersion. It views the wave equation as an integral equation in Fourier space, which can be solved using standard and efficient numerical techniques.
1983-07-08
CALCULATE Sinii.ItrmEMISSION AND TRANSMISSION OF INFRARED Sinii.Itrm RADIATION THROUGH NON-EQUILIBRIUM G. PERFORMING O1G. REPORT NUMBER ATMOSPHERES ERP ...8217 669.726-3 .9144J.1. *S4!468E+14 .S6d36E*14 .99414E414 *669.7265 .695eOE.1. .921910E+14 .94616E+14 .97342E414 ’ Saa hit.tZi!tt f.73 1Eti- .IMU1 -4 SIACIF+±4
Li, Changping
2014-11-10
In this report, we propose a fast numerical solution for the steady state radiative transfer equation in order to calculate the path loss due to light absorption and scattering in various type of underwater channels. In the proposed scheme, we apply a direct non-uniform method to discretize the angular space and an upwind type finite difference method to discretize the spatial space. A Gauss-Seidel iterative method is then applied to solve the fully discretized system of linear equations. The accuracy and efficiency of the proposed scheme is validated by Monte Carlo simulations.
Radiative properties of magnetic neutron stars with metallic surfaces and thin atmospheres
Potekhin, A Y; van Adelsberg, M; Werner, K
2012-01-01
The goal of this work is to develop a simple analytic description of the emission properties (spectrum and polarization) of the condensed, strongly magnetized surface of neutron stars. We have improved the method of van Adelsberg et al. (2005) (arXiv:astro-ph/0406001) for calculating the spectral properties of condensed magnetized surfaces. Using the improved method, we calculate the reflectivity of an iron surface at magnetic field strengths B \\sim (10^{12} - 10^{14}) G, with various inclinations of the magnetic field lines and radiation beam with respect to the surface and each other. We construct analytic expressions for the emissivity of this surface as functions of the photon energy, magnetic field strength, and the three angles that determine the geometry of the local problem. Using these expressions, we calculate X-ray spectra for neutron stars with condensed iron surfaces covered by thin partially ionized hydrogen atmospheres. We develop simple analytic descriptions of the intensity and polarization o...
Radiation properties of the SASE3 afterburner for European XFEL
Wei, Tao; Li, Peng; Li, Yuhui; Pflueger, Joachim
2017-05-01
At present the SASE3 undulator beamline of the European XFEL includes 21 planar undulators which generate horizontally polarized radiation in the soft X-ray region between 0.4 and 5.0nm. In order to satisfy the demand to full polarization control it is planned to install four helical undulator segments at the end of the planar SASE3 undulator system. The helical undulator segments will be used as an afterburner, i.e. they will use the micro-bunched electron beam and produce enhanced coherent radiation at a power level comparable to the linear system but with full polarization control. In this contribution the properties of the emitted radiation will be investigated.
Application of GEANT4 radiation transport toolkit to dose calculations in anthropomorphic phantoms
Rodrigues, P; Peralta, L; Alves, C; Chaves, A; Lopes, M C
2003-01-01
In this paper we present the implementation of a dose calculation application, based on the GEANT4 Monte Carlo toolkit. Validation studies were performed with an homogeneous water phantom and an Alderson--Rando anthropomorphic phantom both irradiated with high--energy photon beams produced by a clinical linear accelerator. As input, this tool requires computer tomography images for automatic codification of voxel based geometries and phase space distributions to characterize the incident radiation field. Simulation results were compared with ionization chamber, thermoluminescent dosimetry data and commercial treatment planning system calculations. In homogeneous water phantom, overall agreement with measurements were within 1--2%. For anthropomorphic simulated setups (thorax and head irradiation) mean differences between GEANT4 and TLD measurements were less than 2%. Significant differences between GEANT4 and a semi--analytical algorithm implemented in the treatment planning system, were found in low density ...
FOOD: an interactive code to calculate internal radiation doses from contaminated food products
Energy Technology Data Exchange (ETDEWEB)
Baker, D.A.; Hoenes, G.R.; Soldat, J.K.
1976-01-01
An interactive code, FOOD, has been written in BASIC for the UNIVAC 1108 to facilitate calculation of internal radiation doses to man from radionuclides in food products. In the dose model, vegetation may be contaminated by either air or irrigation water containing radionuclides. The model considers two mechanisms for radionuclide contamination of vegetation: direct deposition on leaves and uptake from soil through the root system. The user may select up to 14 food categories with corresponding consumption rates, growing periods and either irrigation rates or atmospheric deposition rates. These foods include various kinds of produce, grains and animal products. At present, doses may be calculated for the skin, total body and five internal organs from 190 radionuclides. Dose summaries can be displayed at the local terminal. Further details on percent contribution to dose by nuclide and by food type are available from an auxiliary high-speed printer. This output also includes estimated radionuclide concentrations in soil, plants and animal products.
Effect of the improvement of the HITRAN database on the radiative transfer calculation
Energy Technology Data Exchange (ETDEWEB)
Feng Xuan [National Satellite Meteorological Center, Beijing 100081 (China); Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China)], E-mail: fengfeng7918@hotmail.com; Zhao Fengsheng [National Satellite Meteorological Center, Beijing 100081 (China); Gao Wenhua [National Satellite Meteorological Center, Beijing 100081 (China); Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China)
2007-11-15
The line parameters of the HITRAN 2004 have been updated, as compared with the older editions (the 2000 edition and the 1996 edition). In order to know the effect of the modifications on radiative transfer calculation with high spectral resolution, comparison in optical depth and radiance spectrum have been given between different editions. Four infrared spectral regions are selected, and they cover the three bands of atmospheric infrared sounder (AIRS) and one of geosynchronous imaging fourier transform spectrometer (GIFTS). The comparison has shown that the relative difference between HITRAN 2000 and 2004 and that between HITRAN 1996 and 2004 is decreasing. But the maximal discrepancy between the latest two editions in some spectral intervals is over 1%. It is important to estimate the error of calculation with the line parameters correctly or one has to use the new edition of HITRAN.
X-ray spectra of high temperature tungsten plasma calculated with collisional radiative model
Institute of Scientific and Technical Information of China (English)
Wang Jun; Zhang Hong; Cheng Xin-Lu
2013-01-01
Tungsten is regarded as an important candidate of plasma facing material in international thermonuclear experimental reactor (ITER),so the determination and modeling of spectra of tungsten plasma,especially the spectra at high temperature were intensely focused on recently.In this work,using the atomic structure code of Cowan,a collisional radiative model (CRM) based on the spin-orbit-split-arrays is developed.Based on this model,the charge state distribution of tungsten ions is determined and the soft X-ray spectra from high charged ions of tungsten at different temperatures are calculated.The results show that both the average ionization charge and line positions are well agreed with others calculations and measurements with discrepancies of less than 0.63％ and 1.26％,respectively.The spectra at higher temperatures are also reported and the relationship between ion abundance and temperature is predicted in this work.
A model of the circulating blood for use in radiation dose calculations
Energy Technology Data Exchange (ETDEWEB)
Hui, T.E.; Poston, J.W. Sr.
1987-01-01
Over the last few years there has been a significant increase in the use of radionuclides in leukocyte, platelet, and erythrocyte imaging procedures. Radiopharmaceutical used in these procedures are confined primarily to the blood, have short half-lives, and irradiate the body as they move through the circulatory system. There is a need for a model, to describe the circulatory system in an adult human, which can be used to provide radiation absorbed dose estimates for these procedures. A simplified model has been designed assuming a static circulatory system and including major organs of the body. The model has been incorporated into the MIRD phantom and calculations have been completed for a number of exposure situations and radionuclides of clinical importance. The model will be discussed in detail and results of calculations using this model will be presented.
A model of the circulating blood for use in radiation dose calculations
Energy Technology Data Exchange (ETDEWEB)
Hui, T.E.; Poston, J.W. Sr.
1987-12-31
Over the last few years there has been a significant increase in the use of radionuclides in leukocyte, platelet, and erythrocyte imaging procedures. Radiopharmaceutical used in these procedures are confined primarily to the blood, have short half-lives, and irradiate the body as they move through the circulatory system. There is a need for a model, to describe the circulatory system in an adult human, which can be used to provide radiation absorbed dose estimates for these procedures. A simplified model has been designed assuming a static circulatory system and including major organs of the body. The model has been incorporated into the MIRD phantom and calculations have been completed for a number of exposure situations and radionuclides of clinical importance. The model will be discussed in detail and results of calculations using this model will be presented.
Achakovskiy, Oleg; Tselyaev, Victor; Shitov, Mikhail
2015-01-01
The neutron capture cross sections and average radiative widths of neutron resonances for two double-magic nuclei 132Sn and 208Pb have been calculated using the microscopic photon strength functions, which were obtained within the microscopic self-consistent version of the extended theory of finite Fermi systems in the time blocking approximation. For the first time, the microscopic PSFs have been obtained within the fully self-consistent approach with exact accounting for the single particle continuum (for 208Pb). The approach includes phonon coupling effects in addition to the standard RPA approach. The known Skyrme force has been used. The calculations of nuclear reaction characteristics have been performed with the EMPIRE 3.1 nuclear reaction code. Here, three nuclear level density (NLD) models have been used: the so-called phenomenological GSM, the EMPIRE specific (or Enhanced GSM) and the microscopical combinatorial HFB NLD models. For both considered characteristics we found a significant disagreement ...
The enhanced volume source boundary point method for the calculation of acoustic radiation problem
Institute of Scientific and Technical Information of China (English)
WANG Xiufeng; CHEN Xinzhao; WANG Youcheng
2003-01-01
The Volume Source Boundary Point Method (VSBPM) is greatly improved so that it will speed up the VSBPM's solution of the acoustic radiation problem caused by the vibrating body. The fundamental solution provided by Helmholtz equation is enforced in a weighted residual sense over a tetrahedron located on the normal line of the boundary node to replace the coefficient matrices of the system equation. Through the enhanced volume source boundary point analysis of various examples and the sound field of a vibrating rectangular box in a semi-anechoic chamber, it has revealed that the calculating speed of the EVSBPM is more than 10 times faster than that of the VSBPM while it works on the aspects of its calculating precision and stability, adaptation to geometric shape of vibrating body as well as its ability to overcome the non-uniqueness problem.
Energy Technology Data Exchange (ETDEWEB)
Medeiros, Marcos P.C.; Rebello, Wilson F.; Andrade, Edson R., E-mail: rebello@ime.eb.br, E-mail: daltongirao@yahoo.com.br [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Secao de Engenharia Nuclear; Silva, Ademir X., E-mail: ademir@nuclear.ufrj.br [Corrdenacao dos Programas de Pos-Graduacao em Egenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear
2015-07-01
Nuclear explosions are usually described in terms of its total yield and associated shock wave, thermal radiation and nuclear radiation effects. The nuclear radiation produced in such events has several components, consisting mainly of alpha and beta particles, neutrinos, X-rays, neutrons and gamma rays. For practical purposes, the radiation from a nuclear explosion is divided into {sup i}nitial nuclear radiation{sup ,} referring to what is issued within one minute after the detonation, and 'residual nuclear radiation' covering everything else. The initial nuclear radiation can also be split between 'instantaneous or 'prompt' radiation, which involves neutrons and gamma rays from fission and from interactions between neutrons and nuclei of surrounding materials, and 'delayed' radiation, comprising emissions from the decay of fission products and from interactions of neutrons with nuclei of the air. This work aims at presenting isodose curves calculations at ground level by Monte Carlo simulation, allowing risk assessment and consequences modeling in radiation protection context. The isodose curves are related to neutrons produced by the prompt nuclear radiation from a hypothetical nuclear explosion with a total yield of 20 KT. Neutron fluency and emission spectrum were based on data available in the literature. Doses were calculated in the form of ambient dose equivalent due to neutrons H*(10){sub n}{sup -}. (author)
Properties of radiation-synthesized polyvinylpyrrolidone/chitosan hydrogel blends
Mahmud, Maznah; Daik, Rusli; Adam, Zainah
2015-09-01
Poly(vinylpyrrolidone) (PVP)-crosslinked chitosan hydrogels were prepared by gamma radiation at various doses; 1, 3 5, 7, 10, 15, 20, 25 and 30kGy. Gamma radiation was used as a crosslinking tool which requires no chemical initiator, no heating process and need no purification step on the end products obtained. The hydrogel formulations were composed of 6% chitosan with average molecular weight (Mw) = 48 800 g/mol and 14% PVP with Mw = 10 000 g/mol in 2% lactic acid. Physical properties of hydrogels such as gel fraction and swelling property at pH 5.5 and pH 7.0 as well as syneresis activity were determined. It was found that different radiation dose induces different effect on hydrogels' network formed. Morphological study of hydrogels has been carried out by scanning electron microscope (SEM). From these preliminary evaluations, it can be concluded that gamma radiation is an effective tool for network development of hydrogels and it also induces enhancement on characteristics of hydrogels synthesized.
Properties of radiation-synthesized polyvinylpyrrolidone/chitosan hydrogel blends
Energy Technology Data Exchange (ETDEWEB)
Mahmud, Maznah [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia 43600 Bangi, Selangor (Malaysia); Radiation Processing Technology Division, Malaysian Nuclear Agency, 43000 Kajang, Selangor (Malaysia); Daik, Rusli [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia 43600 Bangi, Selangor (Malaysia); Adam, Zainah [Radiation Processing Technology Division, Malaysian Nuclear Agency, 43000 Kajang, Selangor (Malaysia)
2015-09-25
Poly(vinylpyrrolidone) (PVP)-crosslinked chitosan hydrogels were prepared by gamma radiation at various doses; 1, 3 5, 7, 10, 15, 20, 25 and 30kGy. Gamma radiation was used as a crosslinking tool which requires no chemical initiator, no heating process and need no purification step on the end products obtained. The hydrogel formulations were composed of 6% chitosan with average molecular weight (Mw) = 48 800 g/mol and 14% PVP with Mw = 10 000 g/mol in 2% lactic acid. Physical properties of hydrogels such as gel fraction and swelling property at pH 5.5 and pH 7.0 as well as syneresis activity were determined. It was found that different radiation dose induces different effect on hydrogels’ network formed. Morphological study of hydrogels has been carried out by scanning electron microscope (SEM). From these preliminary evaluations, it can be concluded that gamma radiation is an effective tool for network development of hydrogels and it also induces enhancement on characteristics of hydrogels synthesized.
Improved aerosol radiative properties as a foundation for solar geoengineering risk assessment
Dykema, J. A.; Keith, D. W.; Keutsch, F. N.
2016-07-01
Side effects resulting from the deliberate injection of sulfate aerosols intended to partially offset climate change have motivated the investigation of alternatives, including solid aerosol materials. Sulfate aerosols warm the tropical tropopause layer, increasing the flux of water vapor into the stratosphere, accelerating ozone loss, and increasing radiative forcing. The high refractive index of some solid materials may lead to reduction in these risks. We present a new analysis of the scattering efficiency and absorption of a range of candidate solid aerosols. We utilize a comprehensive radiative transfer model driven by updated, physically consistent estimates of optical properties. We compute the potential increase in stratospheric water vapor and associated longwave radiative forcing. We find that the stratospheric heating calculated in this analysis indicates some materials to be substantially riskier than previous work. We also find that there are Earth-abundant materials that may reduce some principal known risks relative to sulfate aerosols.
Configuration space Faddeev calculations. I. Triton ground state properties
Payne, G. L.; Friar, J. L.; Gibson, B. F.; Afnan, I. R.
1980-08-01
The formulation of Faddeev-type equations in configuration space is discussed. Numerical solutions are obtained using splines and the method of orthogonal collocation. Triton observables and wave-function probabilities are calculated for s-wave NN interaction models of Malfliet and Tjon and the tensor force model of Reid. Comparison with previously published triton results is made; our full five-channel results for the Reid soft-core potential are in excellent agreement with those obtained by Afnan and Birrell using separable expansion methods. NUCLEAR STRUCTURE 3H, Faddeev calculations configuration space.
Energy Technology Data Exchange (ETDEWEB)
Vrigneaud, J.M. [CHU Bichat, nuclear medicine department, 75 - Paris (France); Carlier, T. [CHU Hotel Dieu, nuclear medicine department, 44 - Nantes (France)
2006-07-01
Comparison of the two spreadsheets did not show any significant differences provided that proper biological models were used to follow 131 iodine clearance. This means that even simple assumptions can be used to give reasonable radiation safety recommendations. Nevertheless, a complete understanding of the formalism is required to use correctly these spreadsheets. Initial parameters must be chosen carefully and validation of the computed results must be done. Published guidelines are found to be in accordance with those issued from these spreadsheets. Furthermore, both programs make it possible to collect biological data from each patient and use it as input to calculate individual tailored radiation safety advices. Also, measured exposure rate may be entered into the spreadsheets to calculate patient-specific close contact delays required to reduce the dose to specified limits. These spreadsheets may be used to compute restriction times for any given radiopharmaceutical, provided that input parameters are chosen correctly. They can be of great help to physicians to provide patients with guidance on how to maintain doses to other individuals as low as reasonably achievable. (authors)
Structural and electronic properties of perylene from first principles calculations.
Fedorov, I A; Zhuravlev, Y N; Berveno, V P
2013-03-07
The electronic structure of crystalline perylene has been investigated within the framework of density functional theory including van der Waals interactions. The computations of the lattice parameters and cohesive energy have good agreement with experimental values. We have also calculated the binding distance and energy of perylene dimers, using different schemes, which include van der Waals interactions.
Phase errors and their effect on undulator radiation properties
Directory of Open Access Journals (Sweden)
Richard P. Walker
2013-01-01
Full Text Available A detailed analysis is carried out of the various types of phase errors present in real undulator devices, and their statistical properties. The influence of phase errors on the radiation properties is also examined, distinguishing the effects on peak brightness and integrated flux, and including the effects of electron beam emittance and energy spread. The limitation of the usual expression for the reduction in intensity due to phase errors, based on the rms phase error, is explored, and a new parameter is introduced which correlates better with the reduction in integrated flux. The implications for operation of undulators in future lower emittance storage rings is also discussed.
Infrared radiative properties of alumina up to the melting point: A first-principles study
Yang, J. Y.; Xu, M.; Liu, L. H.
2016-11-01
The high thermal emission of alumina dominates the radiative heat transfer of rocket exhaust plume. Yet numerous experimental measurements on radiative properties of alumina at high temperatures vary considerably from each other and cannot provide physical insight into the underlying mechanism. In this work, the ab initio molecular dynamics (AIMD) method and ab initio parameterized Drude model are combined to predict the radiative properties of alumina for temperatures up to 2327 K (the melting point) in the spectral range 1-12 μm. Contributed by different microscopic processes, the optical absorption of alumina in the spectral range 1-4 and 4-12 μm is described by two distinct methods. In the spectral range 4-12 μm, the multi-phonon process mainly contributes to optical absorption and can be simulated by the AIMD method based on the linear response theory. While in the spectral range 1-4 μm, the optical absorption is mainly caused by intrinsic carriers and can be effectively described by the ab initio parameterized Drude model. The first-principles calculations can successfully predict the infrared radiative properties of alumina at high temperatures and well reproduce the literature experiments. Moreover, the theoretical simulations verify that alumina can retain its semiconducting character even in the liquid phase and there emerges sharp increase in the near-infrared optical absorption of alumina upon melting.
Energy Technology Data Exchange (ETDEWEB)
Mehlhorn, Thomas Alan; Kurecka, Christopher J. (University of Michigan, Ann Arbor, MI); McClarren, Ryan (University of Michigan, Ann Arbor, MI); Brunner, Thomas A.; Holloway, James Paul (University of Michigan, Ann Arbor, MI)
2005-11-01
The original LDRD proposal was to use a nonlinear diffusion solver to compute estimates for the material temperature that could then be used in a Implicit Monte Carlo (IMC) calculation. At the end of the first year of the project, it was determined that this was not going to be effective, partially due to the concept, and partially due to the fact that the radiation diffusion package was not as efficient as it could be. The second, and final year, of the project focused on improving the robustness and computational efficiency of the radiation diffusion package in ALEGRA. To this end, several new multigroup diffusion methods have been developed and implemented in ALEGRA. While these methods have been implemented, their effectiveness of reducing overall simulation run time has not been fully tested. Additionally a comprehensive suite of verification problems has been developed for the diffusion package to ensure that it has been implemented correctly. This process took considerable time, but exposed significant bugs in both the previous and new diffusion packages, the linear solve packages, and even the NEVADA Framework's parser. In order to manage this large suite of problem, a new tool called Tampa has been developed. It is a general tool for automating the process of running and analyzing many simulations. Ryan McClarren, at the University of Michigan has been developing a Spherical Harmonics capability for unstructured meshes. While still in the early phases of development, this promises to bridge the gap in accuracy between a full transport solution using IMC and the diffusion approximation.
Energy Technology Data Exchange (ETDEWEB)
Mehlhorn, Thomas Alan; Kurecka, Christopher J. (University of Michigan, Ann Arbor, MI); McClarren, Ryan (University of Michigan, Ann Arbor, MI); Brunner, Thomas A.; Holloway, James Paul (University of Michigan, Ann Arbor, MI)
2005-11-01
The original LDRD proposal was to use a nonlinear diffusion solver to compute estimates for the material temperature that could then be used in a Implicit Monte Carlo (IMC) calculation. At the end of the first year of the project, it was determined that this was not going to be effective, partially due to the concept, and partially due to the fact that the radiation diffusion package was not as efficient as it could be. The second, and final year, of the project focused on improving the robustness and computational efficiency of the radiation diffusion package in ALEGRA. To this end, several new multigroup diffusion methods have been developed and implemented in ALEGRA. While these methods have been implemented, their effectiveness of reducing overall simulation run time has not been fully tested. Additionally a comprehensive suite of verification problems has been developed for the diffusion package to ensure that it has been implemented correctly. This process took considerable time, but exposed significant bugs in both the previous and new diffusion packages, the linear solve packages, and even the NEVADA Framework's parser. In order to manage this large suite of problem, a new tool called Tampa has been developed. It is a general tool for automating the process of running and analyzing many simulations. Ryan McClarren, at the University of Michigan has been developing a Spherical Harmonics capability for unstructured meshes. While still in the early phases of development, this promises to bridge the gap in accuracy between a full transport solution using IMC and the diffusion approximation.
Xu, Kuan-Man
2005-04-01
This study examines the sensitivity of diagnosed radiative fluxes and heating rates to different treatments of cloud microphysics among cloud-resolving models (CRMs). The domain-averaged CRM outputs are used in this calculation. The impacts of the cloud overlap and uniform hydrometeor assumptions are examined using outputs having spatially varying cloud fields from a single CRM. It is found that the cloud overlap assumption impacts the diagnosis more significantly than the uniform hydrometeor assumption for all radiative fluxes. This is also the case for the longwave radiative cooling rate except for a layer above 7 km where it is more significantly impacted by the uniform hydrometeor assumption. The radiative cooling above upper-tropospheric anvils and the warming below these clouds are overestimated by about 0.5 K day-1 using the domain-averaged outputs. These results are used to further quantify intermodel differences in radiative properties due to different treatments of cloud microphysics among 10 CRMs. The magnitudes of the intermodel differences, as measured by the deviations from the consensus of 10 CRMs, are found to be smaller than those due to the cloud overlap assumption and comparable to those due to the uniform hydrometeor assumption for most shortwave radiative fluxes and the net radiative fluxes at the top of the atmosphere (TOA) and at the surface. For all longwave radiative fluxes, they are smaller than those due to cloud overlap and uniform hydrometeor assumptions. The consensus of all diagnosed radiative fluxes except for the surface downward shortwave flux agrees with observations to a degree that is close to the uncertainties of satellite- and ground-based measurements.
Toxic properties of specific radiation determinant molecules, derived from radiated species
Popov, Dmitri; Maliev, Vecheslav; Kedar, Prasad; Casey, Rachael; Jones, Jeffrey
Introduction: High doses of radiation induce the formation of radiation toxins in the organs of irradiated mammals. After whole body irradiation, cellular macromolecules and cell walls are damaged as a result of long-lived radiation-induced free radicals, reactive oxygen species, and fast, charged particles of radiation. High doses of radiation induce breaks in the chemical bonds of macromolecules and cross-linking reactions via chemically active processes. These processes result in the creation of novel modified macromolecules that possess specific toxic and antigenic properties defined by the type and dose of irradiation by which they are generated. Radiation toxins isolated from the lymph of irradiated animals are classified as hematotoxic, neurotoxic, and enteric non-bacterial (GI) radiation toxins, and they play an important role in the development of hematopoietic, cerebrovascular, and gastrointestinal acute radiation syndromes (ARS). Seven distinct toxins derived from post-irradiated animals have been designated as Specific Radiation Determinants (SRD): SRD-1 (neurotoxic radiation toxin generated by the cerebrovascular form of ARS), SRD-3 (enteric non-bacterial radiation toxins generated by the gastrointestinal form of ARS), and SRD-4 (hematotoxic radiation toxins generated by the hematological, bone marrow form of ARS). SRD-4 is further subdivided into four groups depending on the severity of the ARS induced: SRD-4/1, mild ARS; SRD-4/2, moderate ARS; SRD-4/3, severe ARS; and SRD-4/4, extremely severe ARS. The seventh SRD, SRD-2 is a toxic extract derived from animals suffering from a fourth form of ARS, as described in European literature and produces toxicity primarily in the autonimic nervous system. These radiation toxins have been shown to be responsible for the induction of important pathophysiological, immunological, and biochemical reactions in ARS. Materials and Methods: These studies incorporated the use of statistically significant numbers of a
Radiation toxins: molecular mechanisms of action and radiomimetic properties .
Popov, Dmitri; Maliev, Vecheslav
. Injection of SRD-3 in toxic doses to experimen-tal animals. The clinical symptoms were: increased peristalsis, vomiting, diarrhea with blood. Postmortem section demonstrated multiple petechiae on the cell walls and serous membranes of the abdomen. Experiment N4. Injection of SRD-4 to experimental animals resulted in develop-ment lymphocytopenia, leukocytopenia, trombocytopenia. Autopsy of those animals that died showed changes that are specific a Hematopoietic form of the ARS with development of marked hemorrhagias into tissues of internal organs. Conclusion: 1. Administration of radiation toxins of SRD group to radiation naive animals in toxic doses 0.1 mg/kg; 0,5 mg/kg; 1 mg/kg; 2 mg/kg;3 mg/kg up to 30 mg/kg and more initiates development of specific toxic reactions with symptoms of the ARS. 2.Biological molecules of the Radiation Toxins SRD-group possess both toxic and antigenic properties.
Classic Calculations of Static Properties of the Nucleons revisited
Nasrallah, N F
2016-01-01
Classic calculations of the magnetic moments mu_p and mu_n of the nucleons using the traditional exponential kernel show instability with respect to variations of the Borel mass as well as arbitrariness with respect to the choice of the onset of perturbative QCD. The use of a polynomial kernel, the coefficients of which are determined by the masses of the nucleon resonances stabilizes the calculation and provides much better damping of the unknown contribution of the nucleon continuum. The method is also applied to the evaluation of the coupling gA of proton to the axial current and to the strong part of the neutron-proton mass difference Delta M_np. All these quantities depend sensitively on the value of the 4-quark condensate and the value ~ 1.5^2 reproduces the experimental results.
Computer program for calculating thermodynamic and transport properties of fluids
Hendricks, R. C.; Braon, A. K.; Peller, I. C.
1975-01-01
Computer code has been developed to provide thermodynamic and transport properties of liquid argon, carbon dioxide, carbon monoxide, fluorine, helium, methane, neon, nitrogen, oxygen, and parahydrogen. Equation of state and transport coefficients are updated and other fluids added as new material becomes available.
Accelerating molecular property calculations with nonorthonormal Krylov space methods
Furche, Filipp; Krull, Brandon T.; Nguyen, Brian D.; Kwon, Jake
2016-05-01
We formulate Krylov space methods for large eigenvalue problems and linear equation systems that take advantage of decreasing residual norms to reduce the cost of matrix-vector multiplication. The residuals are used as subspace basis without prior orthonormalization, which leads to generalized eigenvalue problems or linear equation systems on the Krylov space. These nonorthonormal Krylov space (nKs) algorithms are favorable for large matrices with irregular sparsity patterns whose elements are computed on the fly, because fewer operations are necessary as the residual norm decreases as compared to the conventional method, while errors in the desired eigenpairs and solution vectors remain small. We consider real symmetric and symplectic eigenvalue problems as well as linear equation systems and Sylvester equations as they appear in configuration interaction and response theory. The nKs method can be implemented in existing electronic structure codes with minor modifications and yields speed-ups of 1.2-1.8 in typical time-dependent Hartree-Fock and density functional applications without accuracy loss. The algorithm can compute entire linear subspaces simultaneously which benefits electronic spectra and force constant calculations requiring many eigenpairs or solution vectors. The nKs approach is related to difference density methods in electronic ground state calculations and particularly efficient for integral direct computations of exchange-type contractions. By combination with resolution-of-the-identity methods for Coulomb contractions, three- to fivefold speed-ups of hybrid time-dependent density functional excited state and response calculations are achieved.
Shevenell, Lisa
1999-03-01
Values of evapotranspiration are required for a variety of water planning activities in arid and semi-arid climates, yet data requirements are often large, and it is costly to obtain this information. This work presents a method where a few, readily available data (temperature, elevation) are required to estimate potential evapotranspiration (PET). A method using measured temperature and the calculated ratio of total to vertical radiation (after the work of Behnke and Maxey, 1969) to estimate monthly PET was applied for the months of April-October and compared with pan evaporation measurements. The test area used in this work was in Nevada, which has 124 weather stations that record sufficient amounts of temperature data. The calculated PET values were found to be well correlated (R2=0·940-0·983, slopes near 1·0) with mean monthly pan evaporation measurements at eight weather stations.In order to extrapolate these calculated PET values to areas without temperature measurements and to sites at differing elevations, the state was divided into five regions based on latitude, and linear regressions of PET versus elevation were calculated for each of these regions. These extrapolated PET values generally compare well with the pan evaporation measurements (R2=0·926-0·988, slopes near 1·0). The estimated values are generally somewhat lower than the pan measurements, in part because the effects of wind are not explicitly considered in the calculations, and near-freezing temperatures result in a calculated PET of zero at higher elevations in the spring months. The calculated PET values for April-October are 84-100% of the measured pan evaporation values. Using digital elevation models in a geographical information system, calculated values were adjusted for slope and aspect, and the data were used to construct a series of maps of monthly PET. The resultant maps show a realistic distribution of regional variations in PET throughout Nevada which inversely mimics
Cooling load calculation by the radiant time series method - effect of solar radiation models
Energy Technology Data Exchange (ETDEWEB)
Costa, Alexandre M.S. [Universidade Estadual de Maringa (UEM), PR (Brazil)], E-mail: amscosta@uem.br
2010-07-01
In this work was analyzed numerically the effect of three different models for solar radiation on the cooling load calculated by the radiant time series' method. The solar radiation models implemented were clear sky, isotropic sky and anisotropic sky. The radiant time series' method (RTS) was proposed by ASHRAE (2001) for replacing the classical methods of cooling load calculation, such as TETD/TA. The method is based on computing the effect of space thermal energy storage on the instantaneous cooling load. The computing is carried out by splitting the heat gain components in convective and radiant parts. Following the radiant part is transformed using time series, which coefficients are a function of the construction type and heat gain (solar or non-solar). The transformed result is added to the convective part, giving the instantaneous cooling load. The method was applied for investigate the influence for an example room. The location used was - 23 degree S and 51 degree W and the day was 21 of January, a typical summer day in the southern hemisphere. The room was composed of two vertical walls with windows exposed to outdoors with azimuth angles equals to west and east directions. The output of the different models of solar radiation for the two walls in terms of direct and diffuse components as well heat gains were investigated. It was verified that the clear sky exhibited the less conservative (higher values) for the direct component of solar radiation, with the opposite trend for the diffuse component. For the heat gain, the clear sky gives the higher values, three times higher for the peek hours than the other models. Both isotropic and anisotropic models predicted similar magnitude for the heat gain. The same behavior was also verified for the cooling load. The effect of room thermal inertia was decreasing the cooling load during the peak hours. On the other hand the higher thermal inertia values are the greater for the non peak hours. The effect
Transport properties of boron nanotubes investigated by ab initio calculation
Institute of Scientific and Technical Information of China (English)
Guo Wei; Hu Yi-Bin; Zhang Yu-Yang; Du Shi-Xuan; Gao Hong-Jun
2009-01-01
We investigate atomic and electronic structures of boron nanotubes (BNTs) by using the density functional theory(DFT). The transport properties of BNTs with different diameters and chiralities are studied by the Keldysh nonequi-librium Green function (NEGF) method. It is found that the cohesive energies and conductances of BNTs decrease as their diameters decrease. It is more difficult to form (N, 0) tubes than (M, M) tubes when the diameters of the two kinds of tubes are comparable. However, the (N, 0) tubes have a higher conductance than the (M, M) tubes. When the BNTs are connected to gold electrodes, the coupling between the BNTs and the electrodes will affect the transport properties of tubes significantly.
Calculations of the thermodynamic properties of metallurgical solutions
Blander, Milton
Predictive theories for metallurgical solutions are important precursors for computer software in chemical and extractive metallurgy. A limited selection of concepts useful for slags and other ionic systems will be discussed, and include the quasichemical theory, the conformal ionic solution theory, and polymer theory. We emphasize theories which usefully predict solution properties of multicomponent ionic systems, such as silicates and molten salts, to illustrate the range of possible uses.
Parameterization of sea-salt optical properties and physics of the associated radiative forcing
Li, J.; Ma, X.; von Salzen, K.; Dobbie, S.
2008-08-01
The optical properties of sea-salt aerosol have been parameterized at shortwave and longwave wavelengths. The optical properties were parameterized in a simple functional form in terms of the ambient relative humidity based on Mie optical property calculations. The proposed parameterization is tested relative to Mie calculations and is found to be accurate to within a few percent. In the parameterization, the effects of the size distribution on the optical properties are accounted for in terms of effective radius of the sea-salt size distribution. This parameterization differs from previous works by being formulated directly with the wet sea-salt size distribution and, to our knowledge, this is the first published sea-salt parameterization to provide a parameterization for both shortwave and longwave wavelengths. We have used this parameterization in a set of idealized 1-D radiative transfer calculations to investigate the sensitivity of various attributes of sea-salt forcing, including the dependency on sea-salt column loading, effective variance, solar angle, and surface albedo. From these sensitivity tests, it is found that sea-salt forcings for both shortwave and longwave spectra are linearly related to the sea-salt loading for realistic values of loadings. The radiative forcing results illustrate that the shortwave forcing is an order of magnitude greater than the longwave forcing results and opposite in sign, for various loadings. Forcing sensitivity studies show that the influence of effective variance for sea-salt is minor; therefore, only one value of effective variance is used in the parameterization. The dependence of sea-salt forcing with solar zenith angle illustrates an interesting result that sea-salt can generate a positive top-of-the-atmosphere result (i.e. warming) when the solar zenith angle is relatively small (i.e. <30°). Finally, it is found that the surface albedo significantly affects the shortwave radiative forcing, with the forcing
Configuration space Faddeev calculations. I. Triton ground-state properties
Energy Technology Data Exchange (ETDEWEB)
Payne, G.L.; Friar, J.L.; Gibson, B.F.; Afnan, I.R.
1980-08-01
The formulation of Faddeev-type equations in configuration space is discussed. Numerical solutions are obtained using splines and the method of orthogonal collocation. Triton observables and wave-function probabilities are calculated for s-wave NN interaction models of Malfliet and Tjon and the tensor force model of Reid. Comparison with previously published triton results is made; our full five-channel results for the Reid soft-core potential are in excellent agreement with those obtained by Afnan and Birrell using separable expansion methods.
Properties of BGO thin films under the influence of gamma radiation
Energy Technology Data Exchange (ETDEWEB)
Arshak, K. [Electronic and Computer Engineering Department, University of Limerick, Limerick (Ireland)], E-mail: khalil.arshak@ul.ie; Korostynska, O.; Harris, J. [Electronic and Computer Engineering Department, University of Limerick, Limerick (Ireland); Morris, D.; Arshak, A. [Physics Department, University of Limerick, Limerick (Ireland); Jafer, E. [Electronic and Computer Engineering Department, University of Limerick, Limerick (Ireland)
2008-02-15
It is important to know the behaviour of materials under the influence of radiation for the effective design of novel sensor systems. Optical properties of bismuth germinate (Bi{sub 4}Ge{sub 3}O{sub 12}-BGO) thin films were investigated in terms of their perception to gamma radiation exposure. An Edwards E306A vacuum thermal coating system was used for thin films deposition. BGO films with a thickness of 200 nm were exposed to a disk-type {sup 137}Cs gamma radiation source with an activity of 370 kBq. Optical properties of the films were investigated using CARY IE UV-Visible Spectrophotometer. Calculated optical band gap for as-deposited BGO thin film was 1.95 eV. Gamma radiation induced changes in the optical properties of thin films, which could be explained by the variation in the degree of disorder. From the density-of-state model, it is known that optical band gap decreases with an increasing degree of disorder of the amorphous phase. Electrical properties of BGO thin films were recorded in real time using a low power capacitive interface system with a high resolution, which is based on Delta-sigma modulator. At doses from 0 to 1.5 mGy little if any changes in the capacitance were measured. This could be explained by co-existence of two processes, namely creation and annihilation of defects under the influence of radiation. After a threshold dose of 1.5 mGy creation of defects becomes more prevailing and the BGO film capacitance has gradually increased in value from 2.97 pF to 7.09 pF after irradiation with a 2.44 mGy dose.
Matthiä, Daniel; Berger, Thomas
2017-08-01
Galactic cosmic radiation and secondary particles produced in the interaction with the atmosphere lead to a complex radiation field on the Martian surface. A workshop (;1st Mars Space Radiation Modeling Workshop;) organized by the MSL-RAD science team was held in June 2016 in Boulder with the goal to compare models capable to predict this radiation field with each other and measurements from the RAD instrument onboard the curiosity rover taken between November 15, 2015 and January 15, 2016. In this work the results of PLANETOCOSMICS/GEANT4 contributed to the workshop are presented. Calculated secondary particle spectra on the Martian surface are investigated and the radiation field's directionality of the different particles in dependence on the energy is discussed. Omnidirectional particle fluxes are used in combination with fluence to dose conversion factors to calculate absorbed dose rates and dose equivalent rates in a slab of tissue.
Molecular Structure, Theoretical Calculation and Thermodynamic Properties of Tebuconazole
Institute of Scientific and Technical Information of China (English)
MA Haixia; SONG Jirong; HUANG Ting; LU Xingqiang; XU Kangzhen; SUN Xiaohong
2009-01-01
Single crystals of 5-(4-chlorophenyl)-2,2-dimethyl-3-(1,2,4-triazol-1-ylmethyl)-pentom-3-ol (tebuconazole) were obtained in toluene. The single-crystal X-ray diffraction studies showed that it crystallized in the monoclinic system, with space group P2(1)/c and crystal parameters of a= 1.1645(1) nm, b= 1.6768(2) nm, c= 1.7478(2) nm,β=92.055(2)°, Dc= 1.199 g/cm3, Z=4 and F(000)= 1312. Density functional theory (DFT) B3LYP was employed to optimize the structure and calculate the frequencies of tebuconazole. The calculated geometrical parameters are close to the corresponding experimental ones. The specific heat capacity of the title compound was determined with continuous Cp mode of a mircocalorimeter. In the determining temperature range from 283 to 353 K, the special heat capacity of the title compound presents good linear relation with temperature. Using the determined relation-ship of Cp with temperature T, thermodynamic functions (enthalpy, entropy and Gibbs free energy) of the title compound between 283 and 353 K, relative to the standard temperature 298.15 K, were derived through thermody-namic relationship.
Kartashov, D A; Shurshakov, V A
2015-01-01
The paper presents the results of calculating doses from space ionizing radiation for a modeled orbital station cabin outfitted with an additional shield aimed to reduce radiation loads on cosmonaut. The shield is a layer with the mass thickness of -6 g/cm2 (mean density = 0.62 g/cm3) that covers the outer cabin wall and consists of wet tissues and towels used by cosmonauts for hygienic purposes. A tissue-equivalent anthropomorphic phantom imitates human body. Doses were calculated for the standard orbit of the International space station (ISS) with consideration of the longitudinal and transverse phantom orientation relative to the wall with or without the additional shield. Calculation of dose distribution in the human body improves prediction of radiation loads. The additional shield reduces radiation exposure of human critical organs by -20% depending on their depth and body spatial orientation in the ISS compartment.
EFFECTS OF GAMMA RADIATION ON ELECTROCHEMICAL PROPERTIES OF IONIC LIQUIDS
Energy Technology Data Exchange (ETDEWEB)
Visser, A; Nicholas Bridges, N; Thad Adams, T; John Mickalonis, J; Mark02 Williamson, M
2009-04-21
The electrochemical properties of ionic liquids (ILs) make them attractive for possible replacement of inorganic salts in high temperature molten salt electrochemical processing of nuclear fuel. To be a feasible replacement solvent, ILs need to be stable in moderate and high doses of radiation without adverse chemical and physical effects. Here, we exposed seven different ILs to a 1.2 MGy dose of gamma radiation to investigate their physical and chemical properties as they related to radiological stability. The azolium-based ILs experienced the greatest change in appearance, but these ILs were chemically more stable to gamma radiation than some of the other classes of ILs tested, due to the presence of aromatic electrons in the azolium ring. All the ILs exhibited a decrease in their conductivity and electrochemical window (at least 1.1 V), both of which could affect the utility of ILs in electrochemical processing. The concentration of the irradiation decomposition products was less than 3 mole %, with no impurities detectable using NMR techniques.
Svehla, R. A.; Mcbride, B. J.
1973-01-01
A FORTRAN IV computer program for the calculation of the thermodynamic and transport properties of complex mixtures is described. The program has the capability of performing calculations such as:(1) chemical equilibrium for assigned thermodynamic states, (2) theoretical rocket performance for both equilibrium and frozen compositions during expansion, (3) incident and reflected shock properties, and (4) Chapman-Jouguet detonation properties. Condensed species, as well as gaseous species, are considered in the thermodynamic calculation; but only the gaseous species are considered in the transport calculations.
Monte Carlo Calculations for Neutron and Gamma Radiation Fields on a Fast Neutron Irradiation Device
Vieira, A.; Ramalho, A.; Gonçalves, I. C.; Fernandes, A.; Barradas, N.; Marques, J. G.; Prata, J.; Chaussy, Ch.
We used the Monte Carlo program MCNP to calculate the neutron and gamma fluxes on a fast neutron irradiation facility being installed on the Portuguese Research Reactor (RPI). The purpose of this facility is to provide a fast neutron beam for irradiation of electronic circuits. The gamma dose should be minimized. This is achieved by placing a lead shield preceded by a thin layer of boral. A fast neutron flux of the order of 109 n/cm2s is expected at the exit of the tube, while the gamma radiation is kept below 20 Gy/h. We will present results of the neutron and gamma doses for several locations along the tube and different thickness of the lead shield. We found that the neutron beam is very collimated at the end of the tube with a dominant component on the fast region.
Institute of Scientific and Technical Information of China (English)
ZHAO Xinyu; GANG Tie; ZHANG Bixing
2009-01-01
A nonparaxial multi-Gaussian beam model based on the rectangular aperture is proposed in order to overcome the hmitation of paraxial Gaussian beam model which losing accuracy in off-axis beam fields. With the method, acoustical field generated by an ultra-sonic linear phased array transducer is calculated and compared with the corresponding field obtained by Rayleigh-Sommerfeld integral, paraxial multi-Gaussian beam model, and Fraunhof-fer approximation method. Simulation examples show that nonparaxial multi-Gaussian beam model is not limited by the paraxial approximation condition and can predict efficiently and accurately the acoustical field radiated by a linear phased array transducer over a wide range of steering angles.
Calculation of coherent synchrotron radiation impedance using the mode expansion method
Directory of Open Access Journals (Sweden)
G. V. Stupakov
2009-10-01
Full Text Available We study an impedance due to coherent synchrotron radiation (CSR generated by a short bunch of charged particles passing through a dipole magnet of finite length in a vacuum chamber of a given cross section. In our method we decompose the electromagnetic field of the beam over the eigenmodes of the toroidal chamber and derive a system of equations for the expansion coefficients in the series. The general method is further specialized for a toroidal vacuum chamber of a rectangular cross section where the eigenmodes can be computed analytically. We also develop a computer code that calculates the CSR impedance for a toroid of rectangular cross section. Numerical results obtained with the code are presented in the paper.
Ab initio Calculations of Optical Properties of Clusters
Shinde, Ravindra
2016-01-01
We have performed systematic large-scale all-electron correlated calculations on boron Bn, aluminum Aln and magnesium Mgn clusters (n=2--5), to study their linear optical absorption spectra. Several possible isomers of each cluster were considered, and their geometries were optimized at the coupled-cluster singles doubles (CCSD) level of theory. Using the optimized ground-state geometries, excited states of different clusters were computed using the multi-reference singles-doubles configuration interaction (MRSDCI) approach, which includes electron correlation effects at a sophisticated level. These CI wavefunctions were used to compute the transition dipole matrix elements connecting the ground and various excited states of different clusters, eventually leading to their linear absorption spectra. The convergence of our results with respect to the basis sets, and the size of the CI expansion was carefully examined. Isomers of a given cluster show a distinct signature spectrum, indicating a strong structure p...
Institute of Scientific and Technical Information of China (English)
MA, Xiu-Fang; XIAO, Ji-Jun; HUANG, Hui; JU, Xue-Hai; LI, Jin-Shan; XIAO, He-Ming
2006-01-01
Molecular dynamics (MD) method was used to simulate 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) coated with fluorine containing polymers. The mechanical properties and binding energies of PBXs were obtained. It was found that when the number of chain monomers of fluorine containing polymers was the same, the elasticity of TATB/F2314 was increased more greatly than others and the binding energy of TATB/F2311 was the largest among four PBXs. Detonation heat and velocity of such four PBXs were calculated according to theoretical and empirical formulas. The results show that the order of detonation heat is TATB＞TATB/PVDF＞TATB/F2311 ＞TATB/F2314＞TATB/PCTFE while the order of detonation velocity is TATB/PVDF＜TATB/F2311 ＜TATB/F2314＜TATB/PCTFE＜TATB.
Energy Technology Data Exchange (ETDEWEB)
Lenormand, R.; Thiele, M.R. [Institut Francais du Petrole, Rueil Malmaison (France)
1997-08-01
The paper describes the method and presents preliminary results for the calculation of homogenized relative permeabilities
Dynamic simulation of flash drums using rigorous physical property calculations
Directory of Open Access Journals (Sweden)
F. M. Gonçalves
2007-06-01
Full Text Available The dynamics of flash drums is simulated using a formulation adequate for phase modeling with equations of state (EOS. The energy and mass balances are written as differential equations for the internal energy and the number of moles of each species. The algebraic equations of the model, solved at each time step, are those of a flash with specified internal energy, volume and mole numbers (UVN flash. A new aspect of our dynamic simulations is the use of direct iterations in phase volumes (instead of pressure for solving the algebraic equations. It was also found that an iterative procedure previously suggested in the literature for UVN flashes becomes unreliable close to phase boundaries and a new alternative is proposed. Another unusual aspect of this work is that the model expressions, including the physical properties and their analytical derivatives, were quickly implemented using computer algebra.
Structure and Infrared Radiation Properties of Substituted Cordierites
Institute of Scientific and Technical Information of China (English)
XU Qing; SONG Chaowen; CHEN Wen; LIU Xiaofang; ZHANG Feng
2006-01-01
Zn2+ - or Ti4+ -substituted cordierites with the nominal compositions of Mg1.6 Zn0.4 Al4 Si5 O18 and Mg1.8 Ti0.2 Al4.4 Si4.6 O18 respectively, were prepared by a conventional solid state reaction method. The structure of the substituted cordierites was characterized by X- ray diffraction (XRD), infrared ( IR ) spectroscopy and 29 Si magic angle spinning ( MAS ) nuclear magnetic resonance ( NMR ). The infrared radiation properties were investigated in the bands within 2.5-25 μm. Compared with the un-substituted cordierite composition ( Mg2 Al4 Si5 O18 ), Zn2+ - or Ti4+ -substituted cordierites show superior infrared properties . XRD and IR results confirm the formation of hexagonal α-cordierite as the main crystal phase for the substituted cordierites. 29 Si MAS NMR result indicates that Zn2+ or Ti4+ substitutions for partial Mg2+ of a- cordierite promoted the ordering of the distribution of Al and Si atoms in T1 ( tetrahedra connecting six-membered rings together with [ MgO6 ] octahedra ) and T2 ( tetraheda forming six- membered rings ) tetrahedral sites. This resulted in a lattice deformation and increased the anharmonicity of polarization vibration, which is responsible for the improvement of infrared radiation properties of the substituted cordierites.
Energy Technology Data Exchange (ETDEWEB)
Olsson, Paer
2004-04-01
The efficiency of fast neutron reactors, such as for fusion, breeding and transmutation, depend strongly on the neutron radiation resistance of the materials used in the reactors. The binary Fe-Cr alloy, which has many attractive properties in this regard, is the base for the best steels of today which are, however, still not up to the required standards. Therefore, substantial effort has been devoted to finding new materials that can cope with the demands better. Experimental studies must be complemented with extensive theoretical modelling in order to understand the effects that different alloying elements has on the resistance properties of materials. To this end, the first steps of multi-scale modelling has been taken, starting out with ab initio calculations of the electronic structure of the complete concentration range range of the disordered binary Fe-C alloy. The mixing enthalpy of Fe-Cr has been quantitatively predicted and has, together with data from literature, been used in order to fit two sets of interatomic potentials for the purpose of simulating defect evolution with molecular dynamics and kinetic Monte-Carlo codes. These dedicated Fe-Cr alloy potentials are new and represent important additions to the pure element potentials that can be found in literature.
Calculation of radiation reaction effect on orbital parameters in Kerr spacetime
Sago, Norichika
2015-01-01
We calculate the secular changes of the orbital parameters of a point particle orbiting a Kerr black hole, due to the gravitational radiation reaction. For this purpose, we use the post-Newtonian (PN) approximation in the first order black hole perturbation theory, with the expansion with respect to the orbital eccentricity. In this work, the calculation is done up to the fourth post-Newtonian (4PN) order and to the sixth order of the eccentricity, including the effect of the absorption of gravitational waves by the black hole. We confirm that, in the Kerr case, the effect of the absorption appears at the 2.5PN order beyond the leading order in the secular change of the particle's energy and may induce a superradiance, as known previously for circular orbits. In addition, we find that the superradiance may be suppressed when the orbital plane inclines with respect to the equatorial plane of the central black hole. We also investigate the accuracy of the 4PN formulae by comparing to numerical results. If we re...
Exo-Transmit: Radiative transfer code for calculating exoplanet transmission spectra
Kempton, Eliza M.-R.; Lupu, Roxana E.; Owusu-Asare, Albert; Slough, Patrick; Cale, Bryson
2016-11-01
Exo-Transmit calculates the transmission spectrum of an exoplanet atmosphere given specified input information about the planetary and stellar radii, the planet's surface gravity, the atmospheric temperature-pressure (T-P) profile, the location (in terms of pressure) of any cloud layers, the composition of the atmosphere, and opacity data for the atoms and molecules that make up the atmosphere. The code solves the equation of radiative transfer for absorption of starlight passing through the planet's atmosphere as it transits, accounting for the oblique path of light through the planetary atmosphere along an Earth-bound observer's line of sight. The fraction of light absorbed (or blocked) by the planet plus its atmosphere is calculated as a function of wavelength to produce the wavelength-dependent transmission spectrum. Functionality is provided to simulate the presence of atmospheric aerosols in two ways: an optically thick (gray) cloud deck can be generated at a user-specified height in the atmosphere, and the nominal Rayleigh scattering can be increased by a specified factor.
Calculation of coherent synchrotron radiation in toroidal waveguides by paraxial wave equation
Directory of Open Access Journals (Sweden)
D. R. Gillingham
2007-05-01
Full Text Available A new technique for the simulation of coherent synchrotron radiation (CSR and space-charge fields from a single electron bunch in straight or toroidal rectangular waveguide sections has been developed. It is based on the integration of the paraxial approximation to the wave equations, using the perturbation technique where the bending radius is large compared to the dimension of the waveguide. We have implemented an unconditionally stable integration method in the time domain with transparent boundary conditions that allows the use of a minimally sized computational domain about the bunch. This technique explicitly enforces the causality condition so that no portion of the fields can propagate faster than the speed of light, can be used with arbitrary three-dimensional charge distributions, and contains corrections for finite energy. We have also developed a method for the calculation of the transverse forces within the bunch including space-charge. This method has been developed for incorporation with a particle-in-cell code so that we may self-consistently model CSR and space-charge in combinations of bending sections with a fully dynamic electron bunch in an efficient manner. In this paper we describe the model and methods for calculation of the fields in detail and compare results to theory wherever possible.
Coupling hydrodynamics and radiation calculations for star-jet interactions in AGN
de la Cita, Víctor M; Paredes-Fortuny, Xavier; Khangulyan, Dmitry; Perucho, Manel
2016-01-01
Stars and their winds can contribute to the non-thermal (NT) emission in extragalactic jets. Given the complexity of jet-star interactions, the properties of the resulting emission are strongly linked to those of the emitting flows. We simulate the interaction between a stellar wind and a relativistic extragalactic jet and use the hydrodynamic results to compute the NT emission under different conditions. We perform relativistic axisymmetric hydrodynamical simulations of a relativistic jet interacting with a supersonic, non-relativistic stellar wind. We compute the corresponding streamlines out of the simulation results, and calculate the injection, evolution, and emission of NT particles accelerated in the jet shock, focusing on electrons or $e^\\pm$-pairs. Several cases are explored, considering different jet-star interaction locations, magnetic fields and observer lines of sight. The jet luminosity and star properties are fixed, but the results are easily scalable under changes of these parameters. Individu...
Espinosa, G.; Rodríguez, R.; Gil, J. M.; Suzuki-Vidal, F.; Lebedev, S. V.; Ciardi, A.; Rubiano, J. G.; Martel, P.
2017-03-01
Numerical simulations of laboratory astrophysics experiments on plasma flows require plasma microscopic properties that are obtained by means of an atomic kinetic model. This fact implies a careful choice of the most suitable model for the experiment under analysis. Otherwise, the calculations could lead to inaccurate results and inappropriate conclusions. First, a study of the validity of the local thermodynamic equilibrium in the calculation of the average ionization, mean radiative properties, and cooling times of argon plasmas in a range of plasma conditions of interest in laboratory astrophysics experiments on radiative shocks is performed in this work. In the second part, we have made an analysis of the influence of the atomic kinetic model used to calculate plasma microscopic properties of experiments carried out on magpie on radiative bow shocks propagating in argon. The models considered were developed assuming both local and nonlocal thermodynamic equilibrium and, for the latter situation, we have considered in the kinetic model different effects such as external radiation field and plasma mixture. The microscopic properties studied were the average ionization, the charge state distributions, the monochromatic opacities and emissivities, the Planck mean opacity, and the radiative power loss. The microscopic study was made as a postprocess of a radiative-hydrodynamic simulation of the experiment. We have also performed a theoretical analysis of the influence of these atomic kinetic models in the criteria for the onset possibility of thermal instabilities due to radiative cooling in those experiments in which small structures were experimentally observed in the bow shock that could be due to this kind of instability.
Svehla, R. A.; Mcbride, B. J.
1973-01-01
Program performs calculations such as chemical equilibrium for assigned thermodynamic states, theoretical rocket performance for both equilibrium and frozen compositions during expansion, incident and reflected shock properties, and Chapman-Jouget detonation properties. Features include simplicity of input and storage of all thermodynamic and transport property data on master tape.
Monte Carlo-based treatment planning system calculation engine for microbeam radiation therapy
Energy Technology Data Exchange (ETDEWEB)
Martinez-Rovira, I.; Sempau, J.; Prezado, Y. [Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya, Diagonal 647, Barcelona E-08028 (Spain) and ID17 Biomedical Beamline, European Synchrotron Radiation Facility (ESRF), 6 rue Jules Horowitz B.P. 220, F-38043 Grenoble Cedex (France); Institut de Tecniques Energetiques, Universitat Politecnica de Catalunya, Diagonal 647, Barcelona E-08028 (Spain); Laboratoire Imagerie et modelisation en neurobiologie et cancerologie, UMR8165, Centre National de la Recherche Scientifique (CNRS), Universites Paris 7 et Paris 11, Bat 440., 15 rue Georges Clemenceau, F-91406 Orsay Cedex (France)
2012-05-15
Purpose: Microbeam radiation therapy (MRT) is a synchrotron radiotherapy technique that explores the limits of the dose-volume effect. Preclinical studies have shown that MRT irradiations (arrays of 25-75-{mu}m-wide microbeams spaced by 200-400 {mu}m) are able to eradicate highly aggressive animal tumor models while healthy tissue is preserved. These promising results have provided the basis for the forthcoming clinical trials at the ID17 Biomedical Beamline of the European Synchrotron Radiation Facility (ESRF). The first step includes irradiation of pets (cats and dogs) as a milestone before treatment of human patients. Within this context, accurate dose calculations are required. The distinct features of both beam generation and irradiation geometry in MRT with respect to conventional techniques require the development of a specific MRT treatment planning system (TPS). In particular, a Monte Carlo (MC)-based calculation engine for the MRT TPS has been developed in this work. Experimental verification in heterogeneous phantoms and optimization of the computation time have also been performed. Methods: The penelope/penEasy MC code was used to compute dose distributions from a realistic beam source model. Experimental verification was carried out by means of radiochromic films placed within heterogeneous slab-phantoms. Once validation was completed, dose computations in a virtual model of a patient, reconstructed from computed tomography (CT) images, were performed. To this end, decoupling of the CT image voxel grid (a few cubic millimeter volume) to the dose bin grid, which has micrometer dimensions in the transversal direction of the microbeams, was performed. Optimization of the simulation parameters, the use of variance-reduction (VR) techniques, and other methods, such as the parallelization of the simulations, were applied in order to speed up the dose computation. Results: Good agreement between MC simulations and experimental results was achieved, even at
A general model for stray dose calculation of static and intensity-modulated photon radiation
Energy Technology Data Exchange (ETDEWEB)
Hauri, Pascal, E-mail: pascal.hauri2@uzh.ch; Schneider, Uwe [Faculty of Science, University of Zurich, Zurich 8057, Switzerland and Radiotherapy Hirslanden, Hirslanden Medical Center, Aarau 5000 (Switzerland); Hälg, Roger A.; Besserer, Jürgen [Radiotherapy Hirslanden, Hirslanden Medical Center, Aarau 5000 (Switzerland)
2016-04-15
Purpose: There is an increasing number of cancer survivors who are at risk of developing late effects caused by ionizing radiation such as induction of second tumors. Hence, the determination of out-of-field dose for a particular treatment plan in the patient’s anatomy is of great importance. The purpose of this study was to analytically model the stray dose according to its three major components. Methods: For patient scatter, a mechanistic model was developed. For collimator scatter and head leakage, an empirical approach was used. The models utilize a nominal beam energy of 6 MeV to describe two linear accelerator types of a single vendor. The parameters of the models were adjusted using ionization chamber measurements registering total absorbed dose in simple geometries. Whole-body dose measurements using thermoluminescent dosimeters in an anthropomorphic phantom for static and intensity-modulated treatment plans were compared to the 3D out-of-field dose distributions calculated by a combined model. Results: The absolute mean difference between the whole-body predicted and the measured out-of-field dose of four different plans was 11% with a maximum difference below 44%. Computation time of 36 000 dose points for one field was around 30 s. By combining the model-calculated stray dose with the treatment planning system dose, the whole-body dose distribution can be viewed in the treatment planning system. Conclusions: The results suggest that the model is accurate, fast and can be used for a wide range of treatment modalities to calculate the whole-body dose distribution for clinical analysis. For similar energy spectra, the mechanistic patient scatter model can be used independently of treatment machine or beam orientation.
Directory of Open Access Journals (Sweden)
Polednik Martin
2006-11-01
Full Text Available Abstract Background The aim of this study was to compare and to validate different dose calculation algorithms for the use in radiation therapy of small lung lesions and to optimize the treatment planning using accurate dose calculation algorithms. Methods A 9-field conformal treatment plan was generated on an inhomogeneous phantom with lung mimics and a soft tissue equivalent insert, mimicking a lung tumor. The dose distribution was calculated with the Pencil Beam and Collapsed Cone algorithms implemented in Masterplan (Nucletron and the Monte Carlo system XVMC and validated using Gafchromic EBT films. Differences in dose distribution were evaluated. The plans were then optimized by adding segments to the outer shell of the target in order to increase the dose near the interface to the lung. Results The Pencil Beam algorithm overestimated the dose by up to 15% compared to the measurements. Collapsed Cone and Monte Carlo predicted the dose more accurately with a maximum difference of -8% and -3% respectively compared to the film. Plan optimization by adding small segments to the peripheral parts of the target, creating a 2-step fluence modulation, allowed to increase target coverage and homogeneity as compared to the uncorrected 9 field plan. Conclusion The use of forward 2-step fluence modulation in radiotherapy of small lung lesions allows the improvement of tumor coverage and dose homogeneity as compared to non-modulated treatment plans and may thus help to increase the local tumor control probability. While the Collapsed Cone algorithm is closer to measurements than the Pencil Beam algorithm, both algorithms are limited at tissue/lung interfaces, leaving Monte-Carlo the most accurate algorithm for dose prediction.
Chemical Property Calculation through JavaScript and Applications in QSAR
Directory of Open Access Journals (Sweden)
Hanqing Wu
1999-02-01
Full Text Available The inorganic property (I and organic property (O values of general organic groups are re-proposed here. Both I and O values of drug and biological molecules or groups can be calculated based on their common group values. The calculation can be performed easily on-line through JavaScript. Similar calculation can be done for the drug and biological molecular group electronegativity (X according to the author's published paper. The calculation of lipophilicity (ÃÂ€ or logP parameter of (macromolecules (like proteins can also be performed on-line through JavaScript. Two equations expressed with I and O are provided here to define the hydrophobicity of each amino acid. The correlations of inorganic property and organic property values with other parameters are also discussed. These calculated parameters combined with other parameters can be used for QSAR studies in some drug molecules.
Energy Technology Data Exchange (ETDEWEB)
Seguchi, T.; Arakawa, K.; Ito, M.; Hayakawa, N.; Machi, S. (Japan Atomic Energy Research Inst., Takasaki, Gunma. Takasaki Radiation Chemistry Research Establishment)
1983-01-01
The changes of mechanical properties of various kinds of polyethylene (PE) and ethylene-propylene copolymer (EPR) with the irradiation in air, in oxygen of 10 atm, and under vacuum were investigated. The decrease in the elongation (Esub(b)) and the tensile strength (Tsub(b)) of PE by the irradiation in oxygen is larger than under vacuum. The changes of Esub(b) well reflect the degradation of PE. In case of EPR, the Tsub(b) decreases sharply with dose in any environments, and the Esub(b) decreases under vacuum to a larger extent than in oxygen. The modulus at 200% elongation of EPR increases with dose under vacuum, but decreases in oxygen. When the samples were irradiated in air, the changes of the mechanical properties were the intermediate between oxygen and vacuum and dependent on the ratio of oxidation and non-oxidation layers in the film. The antioxidant (Irganox 1010 or DPPD) mixed in polymers was found to retard effectively the polymer degradation by the irradiation in oxygen.
Radiative and combustion properties of nanoparticle-laden liquids
Tyagi, Himanshu
Key processes in energy conversion systems are radiative transport and combustion. The general objective of this dissertation is to improve energy conversion efficiency by a fundamental investigation of how nanoparticle-laden liquid suspensions, generally termed nanofluids, can be used to either enhance radiative absorption in solar thermal energy systems, or to improve the combustion properties of liquid fuels. The present study theoretically investigates the feasibility of using a non-concentrating direct absorption solar collector (DAC) and compares its performance with that of a typical flat-plate collector. Here a nanofluid - a mixture of water and aluminum nanoparticles - is used as the absorbing medium. It was observed that the presence of nanoparticles increases the absorption of incident radiation by more than 9 times over that of pure water. Under similar operating conditions, the efficiency of a DAC using nanofluid as the working fluid is found to be up to 10 percent higher (on an absolute basis) than that of a flat-plate collector. This study also attempts to improve the ignition properties of diesel fuel by investigating the influence of adding aluminum and aluminum-oxide nanoparticles to diesel. As part of this study, droplet ignition experiments were carried out atop a heated hot plate over the range of 688 to 768 degrees centigrade. Different types of fuel mixtures were used; both particle size (15 nm and 50 nm) as well as the volume fraction (0, 0.1 and 0.5 percent) of nanoparticles added to diesel were varied. It was observed that the ignition probability for the fuel mixtures which contained nanoparticles was significantly higher than that of pure diesel. Finally, the concept of using solar energy for converting biomass into useful product-gases was explored. A molten salt mixture (containing nanoparticles) was used to absorb and transfer solar energy to the biomass. Under the highest amount of solar radiation (60 times the normal solar radiation
DEFF Research Database (Denmark)
Lynggaard Riis, Hans; Moltke, Lars N; Zimmermann, S. J.
2016-01-01
prior to treatment. Linac manufacturers offer tools for MV radiation isocentre localization. As a user, there is no access to the documentation for the underlying method and calculation algorithm used in the commercial software. The idea of this work was to evaluate the accuracy of the software tool......Accurate determination of the megavoltage (MV) radiation isocentre of a linear accelerator (linac) is an important task in radiotherapy. The localization of the MV radiation isocentre is crucial for correct calibration of the in-room lasers and the cone-beam CT scanner used for patient positioning...... for MV radiation isocentre calculation as delivered by Elekta using independent software. The image acquisition was based on the scheme designed by the manufacturer. Eight MV images were acquired in each series of a ball-bearing (BB) phantom attached to the treatment couch. The images were recorded...
Radiation damage in silicon. Defect analysis and detector properties
Energy Technology Data Exchange (ETDEWEB)
Hoenniger, F.
2008-01-15
acceptor, a model has been introduced to describe the radiation induced changes in macrsocopic detector properties as affected by the microscopic defect generation. Finally charge collection measurements have been performed at high radiation doses. (orig.)
Institute of Scientific and Technical Information of China (English)
WANGXiufeng; CHENXinzhao; LIUZhao
2003-01-01
The statistical distributed source boundary point method (SDSBPM) put forward is applied to calculate the acoustic radiation from the random vibrating body. A detailed description of this method is presented. A test for the SDSBPM is carried out through the random vibrating sphere and the random vibrating cuboid. An experiment on the exterior acoustic radiation of a random vibrating simulation axial box of the lathe tool is performed in a semi-anechoic chamber.
Recent progress in lattice calculations of properties of open-charm mesons
Mohler, Daniel
2015-01-01
Recent progress in lattice calculations of properties of open-charm mesons, both regular and exotic, is reviewed, with an emphasis on spectroscopy. After reviewing recent calculations of excited state energy levels I will discuss progress in extracting hadronic masses and widths of charmed states from Lattice QCD simulations including low-lying scattering channels directly, to determine phase shift data and bound state/ resonance properties. With regard to other properties results from recent calculations of the $DD^*\\pi$ and $DD\\rho$, $D^*D^*\\rho$ couplings are presented. Beyond regular mesons, searches for explicitly exotic (tetraquark) states are also reviewed.
Ergün, A Sanlı
2011-10-01
Focused ultrasound therapy relies on acoustic power absorption by tissue. The stronger the absorption the higher the temperature increase is. However, strong acoustic absorption also means faster attenuation and limited penetration depth. Hence, there is a trade-off between heat generation efficacy and penetration depth. In this paper, we formulated the acoustic power absorption as a function of frequency and attenuation coefficient, and defined two figures of merit to measure the power absorption: spatial peak of the acoustic power absorption density, and the acoustic power absorbed within the focal area. Then, we derived "rule of thumb" expressions for the optimum frequencies that maximized these figures of merit given the target depth and homogeneous tissue type. We also formulated a method to calculate the optimum frequency for inhomogeneous tissue given the tissue composition for situations where the tissue structure can be assumed to be made of parallel layers of homogeneous tissue. We checked the validity of the rules using linear acoustic field simulations. For a one-dimensional array of 4cm acoustic aperture, and for a two-dimensional array of 4×4cm(2) acoustic aperture, we found that the power absorbed within the focal area is maximized at 0.86MHz, and 0.79MHz, respectively, when the target depth is 4cm in muscle tissue. The rules on the other hand predicted the optimum frequencies for acoustic power absorption as 0.9MHz and 0.86MHz, respectively for the 1D and 2D array case, which are within 6% and 9% of the field simulation results. Because radiation force generated by an acoustic wave in a lossy propagation medium is approximately proportional to the acoustic power absorption, these rules can be used to maximize acoustic radiation force generated in tissue as well.
Poliukhov, Aleksei; Chubarova, Natalia; Kinne, Stephan; Rivin, Gdaliy; Shatunova, Marina; Tarasova, Tatiana
2017-02-01
The radiation block of the COSMO non-hydrostatic mesoscale model of the atmosphere and soil active layer was tested against a relatively new effective CLIRAD(FC05)-SW radiation model and radiative measurements at the Moscow State University Meteorological Observatory (MSU MO, 55.7N, 37.5E) using different aerosol datasets in cloudless conditions. We used the data of shortwave radiation components from the Kipp&Zonen net radiometer CNR4. The model simulations were performed with the application of various aerosol climatologies including the new MACv2 climatology and the aerosol and water vapor dataset from CIMEL (AERONET) sun photometer measurements. The application of the new MACv2 climatology in the CLIRAD(FC05)-SW radiation model provides the annual average relative error of the total global radiation of -3% varying from 0.5% in May to -7.7% in December. The uncertainty of radiative calculations in the COSMO model according to preliminary estimates changes from 1.4% to 8.4%. against CLIRAD(FC05)-SW radiation model with the same parameters. We showed that in clear sky conditions the sensitivity of air temperature at 2 meters to shortwave net radiation changes is about 0.7-0.9°C per100 W/m2 due to the application of aerosol climatologies over Moscow.
Ohga, Yukiharu; Fukuda, Mitsuko; Shibata, Kiyotaka; Kawakami, Takashi; Matsuzaki, Tomokazu
2005-01-01
A system has been developed to improve the efficiency of maintenance work while decreasing the radiation exposure of maintenance personnel in nuclear power plants. The input data for dose rate calculation are automatically generated by using computer-aided design data. Changes for the input data corresponding to the progress of maintenance work, such as installation of a radiation shield and removal of a component, are easily input interactively on a graphical user interface (GUI). A new method was proposed which searches the sets of source and detector points between which gamma-ray attenuation is changed by the component movement. The calculation is performed only for the changed sets, so that the change of the three-dimensional dose rate distribution is calculated rapidly according to the work progress. The dose rate distribution and the radiation exposure of maintenance personnel are displayed three-dimensionally in colour with plant components and pipes on the GUI.
Energy Technology Data Exchange (ETDEWEB)
Kim, Hyoung Tae; Park, Joo Hwan; Rhee, Bo Wook
2006-07-15
To justify the use of a commercial Computational Fluid Dynamics (CFD) code for a CANDU fuel channel analysis, especially for the radiation heat transfer dominant conditions, the CFX-10 code is tested against three benchmark problems which were used for the validation of a radiation heat transfer in the CANDU analysis code, a CATHENA. These three benchmark problems are representative of the CANDU fuel channel configurations from a simple geometry to whole fuel channel geometry. With assumptions of a non-participating medium completely enclosed with the diffuse, gray and opaque surfaces, the solutions of the benchmark problems are obtained by the concept of surface resistance to radiation accounting for the view factors and the emissivities. The view factors are calculated by the program MATRIX version 1.0 avoiding the difficulty of hand calculation for the complex geometries. For the solutions of the benchmark problems, the temperature or the net radiation heat flux boundary conditions are prescribed for each radiating surface to determine the radiation heat transfer rate or the surface temperature, respectively by using the network method. The Discrete Transfer Model (DTM) is used for the CFX-10 radiation model and its calculation results are compared with the solutions of the benchmark problems. The CFX-10 results for the three benchmark problems are in close agreement with these solutions, so it is concluded that the CFX-10 with a DTM radiation model can be applied to the CANDU fuel channel analysis where a surface radiation heat transfer is a dominant mode of the heat transfer.
DEFF Research Database (Denmark)
Xie, Tianwu; Kuster, Niels; Zaidi, Habib
2017-01-01
Computational phantoms are commonly used in internal radiation dosimetry to assess the amount and distribution pattern of energy deposited in various parts of the human body from different internal radiation sources. Radiation dose assessments are commonly performed on predetermined reference...... computational phantoms while the argument for individualized patient-specific radiation dosimetry exists. This study aims to evaluate the influence of body habitus on internal dosimetry and to quantify the uncertainties in dose estimation correlated with the use of fixed reference models. The 5-year-old IT...... absolute effective dose differences between phantoms of different habitus and fixed reference models are 11.4%, 11.3%, 10.8%, 13.3% and 11.4%, respectively. Total body weight, standing height and sitting height have considerable effects on human internal dosimetry. Radiation dose calculations...
Mazonakis, Michalis; Berris, Theocharris; Lyraraki, Efrossyni; Damilakis, John
2015-03-01
This study was conducted to calculate the peripheral dose to critical structures and assess the radiation risks from modern radiotherapy for stage IIA/IIB testicular seminoma. A Monte Carlo code was used for treatment simulation on a computational phantom representing an average adult. The initial treatment phase involved anteroposterior and posteroanaterior modified dog-leg fields exposing para-aortic and ipsilateral iliac lymph nodes followed by a cone-down phase for nodal mass irradiation. Peripheral doses were calculated using different modified dog-leg field dimensions and an extended conventional dog-leg portal. The risk models of the BEIR-VII report and ICRP-103 were combined with dosimetric calculations to estimate the probability of developing stochastic effects. Radiotherapy for stage IIA seminoma with a target dose of 30 Gy resulted in a range of 23.0-603.7 mGy to non-targeted peripheral tissues and organs. The corresponding range for treatment of stage IIB disease to a cumulative dose of 36 Gy was 24.2-633.9 mGy. A dose variation of less than 13% was found by altering the field dimensions. Radiotherapy with the conventional instead of the modern modified dog-leg field increased the peripheral dose up to 8.2 times. The calculated heart doses of 589.0-632.9 mGy may increase the risk for developing cardiovascular diseases whereas the testicular dose of more than 231.9 mGy may lead to a temporary infertility. The probability of birth abnormalities in the offspring of cancer survivors was below 0.13% which is much lower than the spontaneous mutation rate. Abdominoplevic irradiation may increase the lifetime intrinsic risk for the induction of secondary malignancies by 0.6-3.9% depending upon the site of interest, patient’s age and tumor dose. Radiotherapy for stage IIA/IIB seminoma with restricted fields and low doses is associated with an increased morbidity. These data may allow the definition of a risk-adapted follow-up scheme for long
The full spectral radiative properties of Proxima Centauri
Ribas, Ignasi; Gregg, Michael D.; Boyajian, Tabetha S.; Bolmont, Emeline
2017-07-01
Context. The discovery of Proxima b, a terrestrial temperate planet, presents the opportunity of studying a potentially habitable world in optimal conditions. A key aspect in the modeling of its habitability is to understand the radiation environment of the planet in the full spectral domain. Aims: We aim to characterize the X-rays to mid-IR radiative properties of Proxima with the goal of providing the top-of-atmosphere fluxes on the planet. We also aim at constraining the fundamental properties of the star, namely its mass, radius, effective temperature and luminosity. Methods: We have employed observations from a large number of facilities and made use of different methodologies to piece together the full spectral energy distribution of Proxima. In the high-energy domain, we payed particular attention to the contributions of rotational modulation, activity cycle, and flares so that the data provided are representative of the overall radiation dose received by the atmosphere of the planet. Results: We present the full spectrum of Proxima covering 0.7 to 30 000 nm. The integration of the data shows that the top-of-atmosphere average XUV irradiance on Proxima b is 0.293 W m-2, that is, nearly 60 times higher than Earth, and that the total irradiance is 877 ± 44 W m-2, or 64 ± 3% of the solar constant but with a significantly redder spectrum. We also provide laws for the XUV evolution of Proxima corresponding to two scenarios, one with a constant XUV-to-bolometric luminosity value throughout its history and another one in which Proxima left the saturation phase at an age of about 1.6 Gyr and is now in a power-law regime. Regarding the fundamental properties of Proxima, we find M = 0.120 ± 0.003 M⊙, R = 0.146 ± 0.007 R⊙, Teff = 2980 ± 80 K, and L = 0.00151 ± 0.00008 L⊙. In addition, our analysis reveals a 20% excess in the 3-30 μm flux of the star that is best interpreted as arising from warm dust in the system. Conclusions: The data provided here should
Kokhanovsky, Alexander A
2014-01-01
This book describes modern advances in radiative transfer and light scattering. Coverage includes fast radiative transfer techniques, use of polarization in remote sensing and recent developments in remote sensing of snow properties from space observations.
A note on Feynmanʼs calculation of reflection amplitudes for radiation striking a glass surface
Reali, Giancarlo
2014-07-01
In this paper we present a detailed calculation of reflection amplitudes for s- and p-polarized radiation striking a glass surface, closely following the derivation found in the Feynman Lectures on Physics, vol I. The basic idea underlying Feynman's exposition is the extinction theorem, which is used here in a very unique, Feynmanesque way. The calculation is carried out both for the case of radiation coming from the air and from the glass. We also show that the same reasonings are useful to discuss the internal Brewster's law.
Energy Technology Data Exchange (ETDEWEB)
Bordy, J.M.; Kodeli, I.; Menard, St.; Bouchet, J.L.; Renard, F.; Martin, E.; Blazy, L.; Voros, S.; Bochud, F.; Laedermann, J.P.; Beaugelin, K.; Makovicka, L.; Quiot, A.; Vermeersch, F.; Roche, H.; Perrin, M.C.; Laye, F.; Bardies, M.; Struelens, L.; Vanhavere, F.; Gschwind, R.; Fernandez, F.; Quesne, B.; Fritsch, P.; Lamart, St.; Crovisier, Ph.; Leservot, A.; Antoni, R.; Huet, Ch.; Thiam, Ch.; Donadille, L.; Monfort, M.; Diop, Ch.; Ricard, M
2006-07-01
The purpose of this conference was to describe the present state of computer codes dedicated to radiation transport or radiation source assessment or dosimetry. The presentations have been parted into 2 sessions: 1) methodology and 2) uses in industrial or medical or research domains. It appears that 2 different calculation strategies are prevailing, both are based on preliminary Monte-Carlo calculations with data storage. First, quick simulations made from a database of particle histories built though a previous Monte-Carlo simulation and secondly, a neuronal approach involving a learning platform generated through a previous Monte-Carlo simulation. This document gathers the slides of the presentations.
Radiative properties of argon-helium-nitrogen-carbon-cobalt-nickel plasmas used in CNT synthesis
Salem, D.; Hannachi, R.; Cressault, Y.; Teulet, Ph; Béji, L.
2015-02-01
This work presents the radiative properties of argon-helium-nitrogen-carbon-nickel-cobalt thermal plasmas by the computation of net emission coefficients (NECs) under the assumption of a local thermodynamic equilibrium and at temperature range 1000-20 000 K. These mixtures were often used in the study of carbon nanotubes (CNTs) synthesis with arc plasma which becomes one of the most useful techniques in terms of flexibility of carbon nanostructures produced with fewer defects. The values of NEC allow estimation of total radiation losses in plasmas, by taking into account the emission radiation resulting from the atomic continuum, the molecular continuum, the atomic lines and some molecular bands. Free-free transitions (Bremsstrahlung) and free-bound (electron-ion recombination), have been considered for the calculation of atomic continuum. For bound-bound transitions, natural, resonance, Van der Waals, Stark and Doppler effects have been taken into account in the calculation of the lines broadenings while the self-absorption of the resonance lines has been treated using their escape factors. Molecular continuum has been only considered for N2, C2 and CN molecules whereas we have only taken into account diatomic systems N2, \\text{N}2+ , CN and C2 for the emission of the molecular bands. The results obtained show that even for low concentrations of Ni and Co in the plasma, the NECs are modified and considerably increase only at a low temperature (T < 8000 K) and the major contribution in the total radiation arises from the lines emission. However, the effect of the thickness of the plasma on plasma radiation has been analysed based on the self absorption phenomenon of resonance lines.
Bogdanov, O V; Lazarenko, G Yu
2016-01-01
The properties of radiation created by a classical ultrarelativistic scalar charged particle in a constant homogeneous crossed electromagnetic field are described both analytically and numerically with radiation reaction taken into account in the form of the Landau-Lifshitz equation. The total radiation naturally falls into two parts: the radiation formed at the entrance point of a particle into the crossed field (the synchrotron entrance radiation), and the radiation coming from the late-time asymptotics of a particle motion (the de-excited radiation). The synchrotron entrance radiation resembles, although does not coincide with, the ultrarelativistic limit of the synchrotron radiation: its distribution over energies and angles possesses almost the same properties. The de-excited radiation is soft, not concentrated in the plane of motion of a charged particle, and almost completely circularly polarized. The photon energy delivering the maximum to its spectral angular distribution decreases with increasing th...
National Research Council Canada - National Science Library
Ding, Yi; Wang, Yanli
2015-01-01
Using first-principles calculations, we investigate the geometric structures and electronic properties of porous silicene and germanene nanosheets, which are the Si and Ge analogues of α−graphyne...
Fisenko, Anatoliy I.; Lemberg, Vladimir F.
2016-09-01
The knowledge of thermal radiative and thermodynamic properties of uranium and plutonium carbides under extreme conditions is essential for designing a new metallic fuel materials for next generation of a nuclear reactor. The present work is devoted to the study of the thermal radiative and thermodynamic properties of liquid and solid uranium and plutonium carbides at their melting/freezing temperatures. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and normal total emissivity are calculated using experimental data for the frequency dependence of the normal spectral emissivity of liquid and solid uranium and plutonium carbides in the visible-near infrared range. It is shown that the thermal radiative and thermodynamic functions of uranium carbide have a slight difference during liquid-to-solid transition. Unlike UC, such a difference between these functions have not been established for plutonium carbide. The calculated values for the normal total emissivity of uranium and plutonium carbides at their melting temperatures is in good agreement with experimental data. The obtained results allow to calculate the thermal radiative and thermodynamic properties of liquid and solid uranium and plutonium carbides for any size of samples. Based on the model of Hagen-Rubens and the Wiedemann-Franz law, a new method to determine the thermal conductivity of metals and carbides at the melting points is proposed.
Aerosol properties and associated radiative effects over Cairo (Egypt)
El-Metwally, M.; Alfaro, S. C.; Wahab, M. M. Abdel; Favez, O.; Mohamed, Z.; Chatenet, B.
2011-02-01
Cairo is one of the largest megacities in the World and the particle load of its atmosphere is known to be particularly important. In this work we aim at assessing the temporal variability of the aerosol's characteristics and the magnitude of its impacts on the transfer of solar radiation. For this we use the level 2 quality assured products obtained by inversion of the instantaneous AERONET sunphotometer measurements performed in Cairo during the Cairo Aerosol CHaracterization Experiment (CACHE), which lasted from the end of October 2004 to the end of March 2006. The analysis of the temporal variation of the aerosol's optical depth (AOD) and spectral dependence suggests that the aerosol is generally a mixture of at least 3 main components differing in composition and size. This is confirmed by the detailed analysis of the monthly-averaged size distributions and associated optical properties (single scattering albedo and asymmetry parameter). The components of the aerosol are found to be 1) a highly absorbing background aerosol produced by daily activities (traffic, industry), 2) an additional, 'pollution' component produced by the burning of agricultural wastes in the Nile delta, and 3) a coarse desert dust component. In July, an enhancement of the accumulation mode is observed due to the atmospheric stability favoring its building up and possibly to secondary aerosols being produced by active photochemistry. More generally, the time variability of the aerosol's characteristics is due to the combined effects of meteorological factors and seasonal production processes. Because of the large values of the AOD achieved during the desert dust and biomass burning episodes, the instantaneous aerosol radiative forcing (RF) at both the top (TOA) and bottom (BOA) of the atmosphere is maximal during these events. For instance, during the desert dust storm of April 8, 2005 RF BOA, RF TOA, and the corresponding atmospheric heating rate peaked at - 161.7 W/m 2, - 65.8 W/m 2
Energy Technology Data Exchange (ETDEWEB)
Camplin, W C; Brownless, G P; Round, G D; Winpenny, K; Hunt, G J [Centre for Environment, Fisheries and Aquaculture Science, CEFAS Laboratory, Lowestoft (United Kingdom)
2002-12-01
A new method for estimating radiation doses to UK critical groups is proposed for discussion. Amongst others, the Food Standards Agency (FSA) and the Scottish Environment Protection Agency (SEPA) undertake surveillance of UK food and the environment as a check on the effect of discharges of radioactive wastes. Discharges in gaseous and liquid form are made under authorisation by the Environment Agency and SEPA under powers in the Radioactive Substance Act. Results of surveillance by the FSA and SEPA are published in the Radioactivity in Food and the Environment (RIFE) report series. In these reports, doses to critical groups are normally estimated separately for gaseous and liquid discharge pathways. Simple summation of these doses would tend to overestimate doses actually received. Three different methods of combining the effects of both types of discharge in an integrated assessment are considered and ranked according to their ease of application, transparency, scientific rigour and presentational issues. A single integrated assessment method is then chosen for further study. Doses are calculated for surveillance data for the calendar year 2000 and compared with those from the existing RIFE method.
HELIOS-K: An Ultrafast, Open-source Opacity Calculator for Radiative Transfer
Grimm, Simon L
2015-01-01
We present an ultrafast opacity calculator for application to exoplanetary atmospheres, which we name HELIOS-K. It takes a line list as an input, computes the shape of each spectral line (e.g., a Voigt profile) and provides an option for grouping an enormous number of lines into a manageable number of bins. We implement a combination of Algorithm 916 and Gauss-Hermite quadrature to compute the Voigt profile, write the code in CUDA and optimise the computation for graphics processing units (GPUs). We use the k-distribution method to reduce $\\sim 10^5$ to $10^8$ lines to $\\sim 10$ to $10^4$ wavenumber bins, which may then be used for radiative transfer, atmospheric retrieval and general circulation models. We demonstrate that the resampling of the k-distribution function, within each bin, is an insignificant source of error across a broad range of wavenumbers and column masses. By contrast, the choice of line-wing cutoff for the Voigt profile is a significant source of error and affects the value of the compute...
Balan, Etienne; Lazzeri, M.; Mauri, F.; Calas, G.
2007-01-01
We review here some recent applications of ab initio calculations to the modelling of spectroscopic and energetic properties of minerals, which are key components of lateritic soils or govern their geochemical properties. Quantum mechanical ab initio calculations are based on density functional theory and density functional perturbation theory. Among the minerals investigated, zircon is a typical resistant primary mineral. Its resistance to weathering is at the origin of the peculiar geochemi...
Development of paints with infrared radiation reflective properties
Directory of Open Access Journals (Sweden)
Eliane Coser
2015-06-01
Full Text Available AbstractLarge buildings situated in hot regions of the Globe need to be agreeable to their residents. Air conditioning is extensively used to make these buildings comfortable, with consequent energy consumption. Absorption of solar visible and infrared radiations are responsible for heating objects on the surface of the Earth, including houses and buildings. To avoid excessive energy consumption, it is possible to use coatings formulated with special pigments that are able to reflect the radiation in the near- infrared, NIR, spectrum. To evaluate this phenomenon an experimental study about the reflectivity of paints containing infrared-reflective pigments has been made. By irradiating with an IR source and by measuring the surface temperatures of the samples we evaluated: color according to ASTM D 2244-14, UV/VIS/NIR reflectance according to ASTM E 903-12 and thermal performance. Additionally, the spectral reflectance and the IR emittance were measured and the solar reflectance of the samples were calculated. The results showed that plates coated with paints containing IR-reflecting pigments displayed lower air temperature on the opposite side as compared to conventional coatings, indicating that they can be effective to reflect NIR and decrease the temperature of buildings when used in roofs and walls.
Dolinar, E. K.; Dong, X.; Xi, B.
2015-12-01
One-dimensional radiative transfer models (RTM) are a common tool used for calculating atmospheric heating rates and radiative fluxes. In the forward sense, RTMs use known (or observed) quantities of the atmospheric state and surface characteristics to determine the appropriate surface and top-of-atmosphere (TOA) radiative fluxes. The NASA CERES science team uses the modified Fu-Liou RTM to calculate atmospheric heating rates and surface and TOA fluxes using the CERES observed TOA shortwave (SW) and longwave (LW) fluxes as constraints to derive global surface and TOA radiation budgets using a reanalyzed atmospheric state (e.g. temperature and various greenhouse gases) from the newly developed MERRA-2. However, closure studies have shown that using the reanalyzed state as input to the RTM introduces some disparity between the RTM calculated fluxes and surface observed ones. The purpose of this study is to generate a database of observed atmospheric state profiles, from satellite and ground-based sources, at several permanent Atmospheric Radiation Measurement (ARM) Program sites, including the Southern Great Plains (SGP), Northern Slope of Alaska (NSA) and Tropical Western Pacific Nauru (TWP-C2), and Eastern North Atlantic (ENA) permanent facilities. Since clouds are a major modulator of radiative transfer within the Earth's atmosphere, we will focus on the clear-sky conditions in this study, which will set up the baseline for our cloudy studies in the future. Clear-sky flux profiles are calculated using the Edition 4 NASA LaRC modified Fu-Liou RTM. The aforementioned atmospheric profiles generated in-house are used as input into the RTM, as well as from reanalyses. The calculated surface and TOA fluxes are compared with ARM surface measured and CERES satellite observed SW and LW fluxes, respectively. Clear-sky cases are identified by the ARM radar-lidar observations, as well as satellite observations, at the select ARM sites.
First-principles calculations of the near-edge optical properties of β-Ga2O3
Mengle, Kelsey A.; Shi, Guangsha; Bayerl, Dylan; Kioupakis, Emmanouil
2016-11-01
We use first-principles calculations based on many-body perturbation theory to investigate the near-edge electronic and optical properties of β-Ga2O3. The fundamental band gap is indirect, but the minimum direct gap is only 29 meV higher in energy, which explains the strong near-edge absorption. Our calculations verify the anisotropy of the absorption onset and explain the range (4.4-5.0 eV) of experimentally reported band-gap values. Our results for the radiative recombination rate indicate that intrinsic light emission in the deep-ultra-violet (UV) range is possible in this indirect-gap semiconductor at high excitation. Our work demonstrates the applicability of β-Ga2O3 for deep-UV detection and emission.
First principles calculations of the structural and electronic properties of(CdSe)n clusters
Institute of Scientific and Technical Information of China (English)
WANG Xin-qiang; CHEN Yong
2004-01-01
The structural and electronic properties of (CdSe)n(1≤n≤5) clusters are calculated using density functional theory within the pseudopotential and generalized gradient approximations. The calculated binding energies and highest occupied molecular orbitallowest unoccupied molecular orbital gaps are compared with those obtained within local density approximation.
Energy Technology Data Exchange (ETDEWEB)
Deleuze, M.S.; Pickup, B.T.; Wilton, D.J.
2000-04-05
The authors present the theory of the electron propagator perturbed by an external electric field and show how it can be used to calculate a variety of one-electron linear response properties that are accurate through second order in electron correlation. Some illustrative calculations are discussed.
First-principle Calculation of the Properties of Ti3SiC2
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The electronic and structural properties for Ti3SiC2 were studied using the first-principle calculation method. By using the calculated band structure and density of states, the high electrical conductivity of Ti3SiC2 are explained.The bonding character of Ti3SiC2 is analyzed in the map of charge density distribution.
Ludwig, Wolfgang; Eggl, Siegfried; Neubauer, David; Leitner, Johannes; Firneis, Maria; Hitzenberger, Regina
2014-05-01
Recent fields of interest in exoplanetary research include studies of potentially habitable planets orbiting stars outside of our Solar System. Habitable Zones (HZs) are currently defined by calculating the inner and the outer limits of the mean distance between exoplanets and their central stars based on effective solar fluxes that allow for maintaining liquid water on the planet's surface. Kasting et al. (1993), Selsis et al. (2007), and recently Kopparapu et al. (2013) provided stellar flux limits for such scenarios. We compute effective solar fluxes for Earth-like planets using Earth-like and other atmospheric scenarios including atmospheres with high level and low level clouds. Furthermore we provide habitability limits for solvents other than water, i.e. limits for the so called Life Supporting Zone, introduced by Leitner et al. (2010). The Life Supporting Zone (LSZ) encompasses many habitable zones based on a variety of liquid solvents. Solvents like ammonia and sulfuric acid have been identified for instance by Leitner et al (2012) as possibly life supporting. Assuming planets on circular orbits, the extent of the individual HZ is then calculated via the following equation, d(i,o) = [L/Lsun*1/S(i,o)]**0.5 au, where L is the star's luminosity, and d(i,o) and S(i,o) are the distances to the central star for the inner and the outer edge and effective insolation for inner and the outer edge of the HZ, respectively. After generating S(i,o) values for a selection of solvents, we provide the means to determine LSZ boundaries for main sequence stars. Effective flux calculations are done using a one dimensional radiative convective model (Neubauer et al. 2011) based on a modified version of the open source radiative transfer software Streamer (Key and Schweiger, 1998). Modifications include convective adjustments, additional gases for absorption and the use of an offline cloud model, which allow us to observe the influence of clouds on effective stellar fluxes
Energy Technology Data Exchange (ETDEWEB)
Dai, Wei [Hubei Univ. of Education, Wuhan (China). Dept. of Physics and Electronics; Chinese Academy of Engineering Physics, Mianyang (China). Inst. of Fluid Physics; Song, Jin-Fan; Wang, Ping; Lu, Cheng; Lu, Zhi-Wen [Nanyang Normal Univ. (China). Dept. of Physics; Tan, Xiao-Ming [Ludong Univ., Yantai (China). Dept. of Physics
2011-10-15
A theoretical investigation on structural and elastic properties of zinc sulfide semiconductor under high pressure is performed by employing the first-principles method based on the density functional theory. The calculated results show that the transition pressure P{sub t} for the structural phase transition from the B3 structure to the B1 structure is 17.04 GPa. The calculated values are generally speaking in good agreement with experiments and with similar theoretical calculations. (orig.)
Calculation of the thermodynamic properties of liquid Ag–In–Sb alloys
Directory of Open Access Journals (Sweden)
DRAGANA ZIVKOVIC
2006-03-01
Full Text Available The results of calculations of the thermodynamic properties of liquid Ag–In–Sb alloys are presented in this paper. The Redlich–Kister–Muggianu model was used for the calculations. Based on known thermodynamic data for constitutive binary systems and available experimental data for the investigated ternary system, the ternary interaction parameter for the liquid phase in the temperature range 1000–1200 K was determined. Comparison between experimental and calculated results showed their good mutual agreement.
Directory of Open Access Journals (Sweden)
S.A. Rahimi
2005-01-01
Full Text Available Background and purpose : Instalation of protective barrier against diagnostic x-ray is generally done based on the recommendations of NCRP49. There are analytic methods for designing protective barriers howerer, they lack sufficient efficiency and considering the NCRP49 reports, designing mechanical protective barrier in order to protect the initial x-ray radiation and absorption of the ray quality of such radiation is different.Therefore, the protective barrier for each radiation is measured separately. In this study, a computer software was designed to calculate the needed barrier with high accuracy.Materials and methods: Calculation of required protective barrier particularly when two or more generators are in use at diagnostic x-ray units and or installed diagnostic equipments do not have proper room space and the limitations for other clanges in parameters which are time- consuming and impossible to be manually calculated. For proper determination of thichness of the protective barrier, relevant information about curves of radiation weakness, dose limit etc should be entered. This program was done in windows and designed in such a way that the operator works easily, flexibility of the program is acceptable and its accuracy and sensitivity is high.Results : Results of this program indicate that, in most cases, in x-ray units required protective barrier was not used. Meanwhile sometimes shielding is more than what required which lacks technical standards and cost effectiveness. When the application index is contrasting zero, thichness of NCRP49 calculation is about 20% less than the calculated rate done by the method of this study. When the applied index is equal to zero (that is the only situation where the second barrier is considered, thickness of requined barrier is about 15% less than the lead barrier and concrete barrier calculated in this project is 8% less than that calculated by McGuire method.Conclusion : In this study proper
Rodríguez, R; Espinosa, G; Gil, J M; Stehlé, C; Suzuki-Vidal, F; Rubiano, J G; Martel, P; Mínguez, E
2015-05-01
This work is divided into two parts. In the first one, a study of radiative properties (such as monochromatic and the Rosseland and Planck mean opacities, monochromatic emissivities, and radiative power loss) and of the average ionization and charge state distribution of xenon plasmas in a range of plasma conditions of interest in laboratory astrophysics and extreme ultraviolet lithography is performed. We have made a particular emphasis in the analysis of the validity of the assumption of local thermodynamic equilibrium and the influence of the atomic description in the calculation of the radiative properties. Using the results obtained in this study, in the second part of the work we have analyzed a radiative shock that propagated in xenon generated in an experiment carried out at the Prague Asterix Laser System. In particular, we have addressed the effect of plasma self-absorption in the radiative precursor, the influence of the radiation emitted from the shocked shell and the plasma self-emission in the radiative precursor, the cooling time in the cooling layer, and the possibility of thermal instabilities in the postshock region.
Wang, Xinxin; Shi, Deheng; Sun, Jinfeng; Zhu, Zunlue
2016-08-01
The potential energy curves were calculated for the 21 states (X2Π, A2Π, 32Π, 42Π, 52Π, 12Σ+, 22Σ+, 32Σ+, 12Σ-, 22Σ-, 32Σ-, 12Δ, 22Δ, 32Δ, 12Φ, 14Σ+, a4Σ-, 24Σ-, 14Π, 24Π and 14Δ), which originated from the two lowest dissociation channels of ClO radical. The calculations were done for internuclear separations approximately from 0.08 to 1.10 nm using the CASSCF method, which was followed by the icMRCI approach with the aug-cc-pV5Z basis set. Of these 21 states, the 14Π, 24Π, 32Δ, 42Π, 52Π, 12Φ, 32Σ+, 14Δ and 24Σ- states are repulsive. The 12Δ, 12Σ-, 14Σ+, 22Σ-, 12Σ+, 22Σ+, 22Δ and 32Σ- states are very weakly bound. Only the A2Π state has one barrier. The avoided crossing exists between the A2Π and the 32Π state. However, the avoided crossing does not generate any double wells. Core- valence correlation correction was accounted for at the level of an aug-cc-pCVQZ basis set. Scalar relativistic correction was included by the third-order Douglas-Kroll Hamiltonian approximation at the level of an aug-cc-pVQZ basis set. All the potential energy curves were extrapolated to the complete basis set limit. The spectroscopic parameters were determined. The 12Σ-, 22Σ-, 32Σ- and 14Σ+ states may be very difficult to be detected in an experiment, since each of these Λ-S states has only one or two vibrational states. The Franck-Condon factors and radiative lifetimes were calculated for several low vibrational levels of the A2Π - X2Π, 32Π - a4Σ-, 22Δ - a4Σ- and 32Σ- - 12Σ- transitions. The spin-orbit coupling effect on the spectroscopic parameters of the X2Π, A2Π, 32Π, a4Σ- and 22Σ+ states were discussed. The spectroscopic properties reported here can be expected to be reliably predicted ones.
Self-consistent calculations of optical properties of type I and type II quantum heterostructures
Shuvayev, Vladimir A.
In this Thesis the self-consistent computational methods are applied to the study of the optical properties of semiconductor nanostructures with one- and two-dimensional quantum confinements. At first, the self-consistent Schrodinger-Poisson system of equations is applied to the cylindrical core-shell structure with type II band alignment without direct Coulomb interaction between carriers. The electron and hole states and confining potential are obtained from a numerical solution of this system. The photoluminescence kinetics is theoretically analyzed, with the nanostructure size dispersion taken into account. The results are applied to the radiative recombination in the system of ZnTe/ZnSe stacked quantum dots. A good agreement with both continuous wave and time-resolved experimental observations is found. It is shown that size distribution results in the photoluminescence decay that has essentially non-exponential behavior even at the tail of the decay where the carrier lifetime is almost the same due to slowly changing overlap of the electron and hole wavefunctions. Also, a model situation applicable to colloidal core-shell nanowires is investigated and discussed. With respect to the excitons in type I quantum wells, a new computationally efficient and flexible approach of calculating the characteristics of excitons, based on a self-consistent variational treatment of the electron-hole Coulomb interaction, is developed. In this approach, a system of self-consistent equations describing the motion of an electron-hole pair is derived. The motion in the growth direction of the quantum well is separated from the in-plane motion, but each of them occurs in modified potentials found self-consistently. This approach is applied to a shallow quantum well with the delta-potential profile, for which analytical expressions for the exciton binding energy and the ground state eigenfunctions are obtained, and to the quantum well with the square potential profile with several
Parameterization of sea-salt optical properties and physics of the associated radiative forcing
Directory of Open Access Journals (Sweden)
J. Li
2008-03-01
Full Text Available The optical properties of sea-salt aerosol have been parameterized at solar and longwave wavelengths. The optical properties were parameterized in a simple functional form in terms of the ambient relative humidity based on Mie optical property calculations. The proposed parameterization is tested relative to Mie calculations and is found to be accurate to within a few percent. In the parameterization, the effects of the size distribution on the optical properties are accounted for in terms of effective radius of the sea-salt size distribution. This parameterization differs from previous works by being formulated directly with the wet sea-salt size distribution (and compared to AERONET results and, to our knowledge, this is the first published sea-salt parameterization to provide a parameterization for both solar and longwave wavelengths. We have used this parameterization in a set of idealized 1-D radiative transfer calculations to investigate the sensitivity of various attributes of sea-salt forcing, such as dependence with sea-salt column loading, effective variance, solar angle, and surface albedo. From these sensitivity tests, it is found that sea-salt forcings for both solar and longwave spectra are linearly related to the sea-salt loading for realistic values of loadings. The radiative forcing results illustrate that the shortwave forcing is an order of magnitude greater than the longwave forcing results and opposite in sign, for various loadings. Studies of the sensitivity of forcing results to variations in effective variance show there to be minimal variation; therefore, only one value of effective variance is used in the parameterization. The dependence of sea-salt forcing with solar angle illustrates an interesting result that sea-salt can generate a positive top-of-the-atmosphere result (i.ewarming when the solar zenith angle is relatively small 30° Finally, it is found that the surface albedo significantly affects the solar
A more accurate formula for calculating the net longwave radiation flux in the Baltic Sea
Directory of Open Access Journals (Sweden)
Tomasz Zapadka
2007-12-01
Full Text Available A new, more accurate formula for calculating the net longwave radiation fluxLW ↑↓ has been devised for the Baltic Sea region. To this end,the following sets of simultaneously measured data regarding the longwave radiation of the sea andthe atmosphere were used: the temperatures of the sea surface and its contiguous air layer,the water vapour pressure in the air above the water, and the cloud cover.These data were gathered during numerous research cruises in the Baltic in 2000-03 and were supplemented by satellitedata from Karlsson (2001 characterising the cloud cover over the whole Baltic. The formulaestablished for LW ↑↓ can be written in the form of three alternative equations,differing with respect to their cloud cover functions:LW ↑↓ =0.985σT4s - σT4a (0.685+0.00452e{(1 + d n2 average for all cloud types (Z1(1 + din2 separately for low-, mid- and high-level clouds (Z2(1 + dinϒi separately for low-, mid- and high-level clouds (Z3where σ - Stefan-Boltzmann constant; Ts - sea surface temperature [K]; Ta - air temperature [K]; e - water vapour pressure [mbar]; n - total cloud amount [0 - 1]; d - mean empirical dimensionless coefficient, determined for all cloud types or for particular months (see Tables 3 and 4; da - empirical coefficient determined for the quadratic function: d1 = 0.39 for low-level clouds, d2 = 0.305 for mid-level clouds, d3 = 0.22 for high-level clouds; di - empirical coefficient determined as follows: d1 = 0.39 for low-level clouds when γ1 = 1.3, d2 = 0.29 for mid-level clouds when γ2 = 1.1; d3 = 0.17 for high-level clouds when γ3 = 0.96. The improved accuracy of this formula (RMSE ≅ 10 W m-2 is due chiefly to the establishment of functions and coefficients characterising the cloud cover over the Baltic in particular months of the year and their incorporation into it.
Calculation of Tissue-Air Ratios(TAR) in Irregularly shaped Field for Co-60 Gamma Radiation
Energy Technology Data Exchange (ETDEWEB)
Ji, Young Hoon [Dept. of Therapetic Radiology, Kangnam General Hospital, Seoul (Korea, Republic of)
1989-05-15
In order to calculate the dose on each interest point in five types of irregularly shaped fields used commonly in radiotherapy, the tissue-air ratios (TAR) in these fields for Go-60 gamma radiation were calculated using the newly devised SAR-chart. The TARs calculated from newly method of using the SAR-chart, computer method and approximation method at the interest point were compared to the TARs obtained from measurement. The result are as follows; In case of the interest points on central axis the calculated TARs in irregularly shaped fields by the above mentioned methods were well agreed within the error of , whereas for the interest points on off-axis the calculated TARs were resulted in the maximum errors of and respectively. From these results, the accuracy of calculation method of using the SAR-chart was confirmed.
Energy Technology Data Exchange (ETDEWEB)
Soldat, J.K.
1989-10-01
This report compares the results of the calculation of potential radiation doses to the public by two different environmental dosimetric systems for the years 1983 through 1987. Both systems project the environmental movement of radionuclides released with effluents from Hanford operations; their concentrations in air, water, and foods; the intake of radionuclides by ingestion and inhalation; and, finally, the potential radiation doses from radionuclides deposited in the body and from external sources. The first system, in use for the past decade at Hanford, calculates radiation doses in terms of 50-year cumulative dose equivalents to body organs and to the whole body, based on the methodology defined in ICRP Publication 2. This system uses a suite of three computer codes: PABLM, DACRIN, and KRONIC. In the new system, 50-year committed doses are calculated in accordance with the recommendations of the ICRP Publications 26 and 30, which were adopted by the US Department of Energy (DOE) in 1985. This new system calculates dose equivalent (DE) to individual organs and effective dose equivalent (EDE). The EDE is a risk-weighted DE that is designed to be an indicator of the potential health effects arising from the radiation dose. 16 refs., 1 fig., 38 tabs.
Katz, D.; Cwik, T.; Sterling, T.
1998-01-01
This paper uses the parallel calculation of the radiation integral for examination of performance and compiler issues on a Beowulf-class computer. This type of computer, built from mass-market, commodity, off-the-shelf components, has limited communications performance and therefore also has a limited regime of codes for which it is suitable.
DEFF Research Database (Denmark)
Zimmermann, S. J.; Rowshanfarzad, P.; Ebert, M. A.
2015-01-01
radiation isocentre prior to routine use of the cone-beam CT system. The isocentre determination method used in the XVI software is not available to users. The aim of this work is to perform an independent evaluation of the Elekta XVI 4.5 software for isocentre verification with focus on the robustness......Purpose/Objective: Most modern radiotherapy treatments are based on cone-beam CT images to ensure precise positioning of the patient relative to the linac. This requires alignment of the cone-beam CT system to the linac MV radiation isocentre. Therefore, it is important to precisely localize the MV......) and the radiation field centre (RFC) is calculated. A software package was developed for accurate calculation of the linac isocentre position. This requires precise determination of the position of the ball bearing and the RFC. Results: Data were acquired for 6 MV, 18 MV and flattening filter free (FFF) 6 MV FFF...
Takahashi, F; Shigemori, Y; Seki, A
2009-01-01
A system has been developed to assess radiation dose distribution inside the body of exposed persons in a radiological accident by utilising radiation transport calculation codes-MCNP and MCNPX. The system consists mainly of two parts, pre-processor and post-processor of the radiation transport calculation. Programs for the pre-processor are used to set up a 'problem-dependent' input file, which defines the accident condition and dosimetric quantities to be estimated. The program developed for the post-processor part can effectively indicate dose information based upon the output file of the code. All of the programs in the dosimetry system can be executed with a generally used personal computer and accurately give the dose profile to an exposed person in a radiological accident without complicated procedures. An experiment using a physical phantom was carried out to verify the availability of the dosimetry system with the developed programs in a gamma ray irradiation field.
Exploring gamma radiation effect on exoelectron emission properties of bone
Energy Technology Data Exchange (ETDEWEB)
Zakaria, M.; Dekhtyar, Y.; Bogucharska, T.; Noskov, V. [Riga Technical Univ., Biomedical Engineering and Nanotechnology Institute (Latvia)
2006-07-01
Gamma radiation is used for radiation therapy to treat carcinogenic diseases including bone cancer. Ionising radiation kills carcinogenic calls. However, there are side effects of the gamma radiation on the bone surface electron structure. One of the effects is in the form of altering electron density of states of bone that, with time, influences biomedical reactions on bone life condition. (authors)
Chen, W.; Chou, C.; Lin, P.; Wang, S.
2011-12-01
The planetary boundary layer is the air layer near the ground directly affected by diurnal heat, moisture, aerosol, and cloud transfer to or from the surface. In the daytime solar radiation heats the surface, initiating thermal instability or convection. Whereas, the scattering and absorption of aerosols or clouds might decrease the surface radiation or heat atmosphere which induce feedbacks such as the enhanced stratification and change in relative humidity in the boundary layer. This study is aimed to understand the possible radiative effect of aerosols basing on ground based aerosol measurements and lidar installed in National Taiwan University in Taipei. The optical and radiative properties of aerosols are dominated by aerosol composition, particle size, hygroscopicity property, and shape. In this study, aerosol instruments including integrating nephelometer, open air nephelometer, aethalometer are applied to investigate the relationship between aerosol hygroscopicity properties and aerosol types. The aerosol hygroscopicity properties are further applied to investigate the effect of relative humidity on aerosol vertical profiles measured by a dual-wavelength and depolarization lidar. The possible radiative effect of aerosols are approached by vertical atmospheric extinction profiles measured by lidar. Calculated atmospheric and aerosol heating effects was compared with vertical meteorological parameters measured by radiosonde. The result shows light-absorbing aerosol has the potential to affect the stability of planetary boundary layer.
Numerical calculation of radiation protective clothing efficiency by using Monte Carlo method
Моргунов, Владимир Викторович; Диденко, Наталья Викторовна; Трищ, Роман Михайлович
2016-01-01
The article presents the results of numerical experiments on modeling of absorption of gamma-radiation with/without using the proposed radiation-protective suit and radiation-shielding material (lead glass in the form of microspheres). The proposed method numerical experiments leads to the reduction of human, time and financial resources. When conducting numerical experiments we used the software package GEANT4. When conducting numerical experiments, we used a phantom of the human body (total...
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
[Objective] The aim was to study the distribution characteristics of terrain reflected radiation in Fujian Province.[Method] Based on solar radiation data,digital elevation model (DEM) and surface meteorological observation data in Fujian Province,plus surface albedo obtained by using remote sensing inversion method,the distribution of terrain reflected radiation in Fujian Province from 1988 to 2007 was simulated,and then its temporal and spatial distribution characteristics was studied.[Result] The simulat...
Directory of Open Access Journals (Sweden)
Grigory E. Brill
2014-09-01
Full Text Available Purpose — to investigate the effects of low-intensity electromagnetic radiation on the process of dehydration selforganization of bacterial lipopolysaccharide (LPS. Material and Methods — The method of wedge dehydration has been used to study the structure formation of bacterial LPS. Image-phases analysis included their qualitative characteristics, as well as the calculation of quantitative indicators, followed by statistical analysis. Results — Low-intensity ultra high frequency (UHF radiation (1 GHz, 0.1 μW/cm2, 10 min has led to the changes in the suspension system of the LPS-saline reflected in the kinetics of structure formation. Conclusion — 1 GHz corresponds to the natural frequency of oscillation of water clusters and, presumably, the effect of UHF on structure of LPS mediates through the changes in water-salt environment. Under these conditions, properties of water molecules of hydration and possibly the properties of hydrophobic and hydrophilic regions in the molecule of LPS, which can affect the ability of toxin molecules to form aggregates change. Therefore the LPS structure modification may result in the change of its toxic properties.
Directory of Open Access Journals (Sweden)
Brill G.E.
2013-12-01
Full Text Available Purpose: to investigate the effects of low-intensity electromagnetic radiation on the process of dehydration self-organization of bacterial lipopolysaccharide. Materials and Methods. The method of wedge dehydration has been used to study the structure formation of bacterial lipopolysaccharide. Image-phases analysis included their qualitative characteristics, as well as the calculation of quantitative indicators, followed by statistical analysis. Results. UHF-Radiation (1GHz, 0,1 uW/cm2, 10 min has led to the changes in the suspension system of the LPS-saline reflected in the kinetics of structure formation. Conclusion. 1 GHz corresponds to the natural frequency of oscillation of water clusters and, presumably, the effect of UHF on structure of LPS mediates through the changes in water-salt environment. Under these conditions, properties of water molecules of hydration and possibly the properties of hydrophobic and hydrophilic regions in the molecule of LPS, which can affect the ability of toxin molecules to form aggregates change. Therefore the lipopolysaccharide structure modification may result in the change of its toxic properties.
Nilsson, C.-M.; Jones, C. J. C.; Thompson, D. J.; Ryue, J.
2009-04-01
Engineering methods for modelling the generation of railway rolling noise are well established. However, these necessarily involve some simplifying assumptions to calculate the sound powers radiated by the wheel and the track. For the rail, this involves using an average vibration together with a radiation efficiency determined for a two-dimensional (2D) problem. In this paper, the sound radiation from a rail is calculated using a method based on a combination of waveguide finite elements and wavenumber boundary elements. This new method allows a number of the simplifying assumptions in the established methods to be avoided. It takes advantage of the 2D geometry of a rail to provide an efficient numerical approach but nevertheless takes into account the three-dimensional nature of the vibration and sound field and the infinite extent of the rail. The approach is used to study a conventional 'open' rail as well as an embedded tram rail of the type used for street running. In the former case it is shown that the conventional approach gives correct results and the complexity of the new method is mostly not necessary. However, for the embedded rail it is found that it is important to take into account the radiation from several wave types in the rail and embedding material. The damping effect of the embedding material on the rail vibration is directly taken into account and, for the example shown, causes the embedded rail to radiate less sound than the open rail above about 600 Hz. The free surface of the embedding material amplifies the sound radiation at some frequencies, while at other frequencies it moves out of phase with the rail and reduces the radiation efficiency. At low frequencies the radiation from the embedded rail resembles a line monopole source which produces greater power than the 'open' rail which forms a line dipole.
Energy Technology Data Exchange (ETDEWEB)
Borodkin, P.G.; Borodkin, G.I.; Khrennikov, N.N. [Scientific and Engineering Centre for Nuclear and Radiation Safety SEC NRS, Building 5, Malaya Krasnoselskaya Street, 2/8, 107140 Moscow (Russian Federation)
2011-07-01
The approach of improved uncertainty-accounted conservative evaluation of vodo-vodyanoi energetichesky reactor (VVER) (reactor-) pressure-vessel (RPV) radiation loading parameters has been proposed. This approach is based on the calculational-experimental procedure, which takes into account C/E ratio, depending on over- or underestimation, and uncertainties of measured and calculated results. An application of elaborated approach to the full-scale ex-vessel neutron dosimetry experiments on Russian VVERs combined with neutron-transport calculations has been demonstrated in the paper. (authors)
Prediction of air-fuel and oxy-fuel combustion through a generic gas radiation property model
DEFF Research Database (Denmark)
Yin, Chungen
2017-01-01
Thermal radiation plays an important role in heat transfer in combustion furnaces. The weighted-sum-of-gray-gases model (WSGGM), representing a good compromise between computational efficiency and accuracy, is commonly used in computational fluid dynamics (CFD) modeling of combustion processes...... for evaluating gaseous radiative properties. However, the WSGGMs still have some limitations in practical use, e.g., unable to naturally accommodate different combustion environments, difficult to accurately address the variations in species concentrations in a flame, and inconvenient to account for the impacts...... of participating species other than H2O and CO2. As a result, WSGGMs with different coefficients have been published for specific applications. In this paper, a reliable generic model for gaseous radiation property calculation, which is a computationally efficient exponential wide band model (E-EWBM) applicable...
Fisenko, Anatoliy I
2016-01-01
The knowledge of thermal radiative and thermodynamic properties of uranium and plutonium carbides under extreme conditions is essential for designing a new metallic fuel materials for next generation of a nuclear reactor. The present work is devoted to the study of the thermal radiative and thermodynamic properties of liquid and solid uranium and plutonium carbides at their melting/freezing temperatures. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and normal total emissivity are calculated using experimental data for the frequency dependence of the normal spectral emissivity of liquid and solid uranium and plutonium carbides in the visible-near infrared range. It is shown that the thermal radiative and thermodynamic functions of uranium carbide have a slight difference during liquid-to-solid transition. Unlike UC, such a difference between these ...
Ferrare, Richard; Feingold, Graham; Ghan, Steven; Ogren, John; Schmid, Beat; Schwartz, Stephen E.; Sheridan, Pat
2006-01-01
Atmospheric aerosols influence climate by scattering and absorbing radiation in clear air (direct effects) and by serving as cloud condensation nuclei, modifying the microphysical properties of clouds, influencing radiation and precipitation development (indirect effects). Much of present uncertainty in forcing of climate change is due to uncertainty in the relations between aerosol microphysical and optical properties and their radiative influences (direct effects) and between microphysical properties and their ability to serve as cloud condensation nuclei at given supersaturations (indirect effects). This paper introduces a special section that reports on a field campaign conducted at the Department of Energy Atmospheric Radiation Measurement site in North Central Oklahoma in May, 2003, examining these relations using in situ airborne measurements and surface-, airborne-, and space-based remote sensing.
All-electron versus pseudopotential calculation of optical properties: the case of GaAs
Energy Technology Data Exchange (ETDEWEB)
Monachesi, P.; Marini, A.; Onida, G.; Palummo, M.; Sole, R. del [Tor Vergata Univ., Rome (Italy). Dipt. di Fisica
2001-03-16
The reliability of the widespread practice of calculating the optical properties of solids using pseudo wavefunctions instead of the true electron wavefunctions has been tested in the case of bulk GaAs. Pseudopotential calculations of the imaginary part of the dielectric function - where the matrix elements of the momentum operator are calculated between pseudo wavefunctions - have been compared with all-electron full-potential linear muffin-tin orbital calculations where the true wavefunctions are used. No evidence has been found of differences due to the different sets of wavefunctions employed in the two approaches. (orig.)
Optical, elastic and thermal properties of ZB-AlN semiconductor from first-principle calculations
Kumar, V.; Singh, Bhanu P.; Chandra, Satish
2016-12-01
The optical, elastic and thermal properties of zincblende aluminium nitride have been studied. The refractive index, absorption coefficient, reflectivity, dielectric constant, extinction coefficient, and energy-loss spectrum have been calculated using the pseudo-potential method under density functional theory at different pressures. The heat capacity, Debye temperature and phonon frequencies have been calculated using CASTEP code at 0 GPa. The elastic stiffness constants, bulk modulus, Young's modulus, shear modulus and pressure derivatives of elastic constants have also been calculated. The calculated results are compared with the available experimental and theoretical data. Reasonably good agreement has been found between them.
Density functional theory approach for calculation of dielectric properties of warm dense matter
Saitov, Ilnur
2015-06-01
The reflectivity of shocked xenon was measured in the experiments of Mintsev and Zaporoghets for wavelength 1064 nm. But there is no adequate theoretical explanation of these reflectivity results in the framework of the standard methods of nonideal plasma theory. The assumption of significant width to the shock front gives a good agreement with the experimental data. However, there are no evidences of this effect in the experiment. Reflectivity of shocked compressed xenon plasma is calculated in the framework of the density functional theory approach as in. Dependencies on the frequency of incident radiation and on the plasma density are analyzed. The Fresnel formula for the reflectivity is used. The longitudinal expression in the long wavelength limit is applied for the calculation of the imaginary part of the dielectric function. The real part of the dielectric function is calculated by means of the Kramers-Kronig transformation. The approach for the calculation of plasma frequency is developed.
LMP, Campos; Boaro, LC; LKG, Santos; Parra, DF; Lugão, AB
2015-10-01
Dental restorative composites are activated by visible light and the polymerization process, known as direct technique, is initiated by absorbing light in a specific wavelength range (450-500 nm). However this technique presented some disadvantages. If light is not inserted correctly, layers uncured can cause countless damage to restoration, especially with regard to mechanical properties. A clinical alternative used to reduce the shortcomings of direct application is the use of composite resins for indirect application. These composites are adaptations of resins prepared for direct use, with differences mainly in the healing process. Besides the traditional photoactivation, indirect application composites may be submitted to particular curing conditions, such as a slow curing rate, heating, vacuum, and inert-gas pressure leading to an oxygen-free environment. However few studies have been conducted on the process of post-curing by ionizing radiation at low doses. On this sense the purpose of this study was to evaluate possible interactions of ionizing radiation in the post-curing process of the experimental composites based on BisGMA/TEGDMA filled with silica Aerosil OX-50 silanized. Characterization of the experimental composites was performed by thermogravimetry analysis, infrared spectroscopy, elastic modulus and flexural strength. Statistical analysis of results was calculated by one-way ANOVA/Tukey's test. Cross-linking of the polymeric matrix caused by ionizing radiation, influenced the thermal stability of irradiated specimens. FTIR analysis showed that the ionizing radiation induced a post-cure reaction in the specimens. The irradiation dose influenced directly the mechanical properties that showed a strong positive correlation between flexural strength and irradiation and between modulus strength and irradiation.
Doiron, Charles; Hencken, Kai
2013-09-01
Computational fluid-dynamic simulations nowadays play a central role in the development of new gas circuit breakers. For these simulations to be reliable, a good knowledge of the pressure and temperature-dependence of the thermodynamic and transport properties of ionized gases is required. A key ingredient in the calculation of thermodynamic properties of thermal plasmas is the calculation of the chemical equilibrium composition of the gas. The general-purpose, open-source software toolkit Cantera provides most functionality required to carry out such thermodynamic calculations. In this contribution, we explain how we tailored Cantera specifically to calculate material properties of plasmas. The highly modular architecture of this framework made it possible to add support for Debye-Hückel non-ideality corrections in the calculation of the chemical equilibrium mixture, as well as to enable the calculation of the key transport parameters needed in CFD-based electric arc simulations: electrical and thermal conductivity, viscosity, and diffusion coefficients. As an example, we discuss the thermodynamic and transport properties of mixtures of carbon dioxide and copper vapor.
Directory of Open Access Journals (Sweden)
Elso Manuel Cruz Cruz
2010-11-01
Full Text Available Background: The side chains attached to the 7-amino cephalosporanic acid, the structural basis of cephalosporin, condition its molecular properties and cause differences in its pharmacological action. Molecular modeling contributes to further knowledge about this relationship. Objective: To calculate structural and electronic properties of five cephalosporins: cephradine, cephalexin, cefadroxil, cefprozil and ceftobiprole. Methods: A theoretical study using quantum mechanics methods to model the structure and electronic properties of the cephalosporins listed above was conducted. Molecular geometries were optimized with semi-empirical calculations, according to the parameterized number three model. The molecular properties were calculated following the density functional theory. The densities of atomic charges and the frontier orbitals were analyzed. Comparisons were established to measure the effect of substituents on the properties of the beta-lactam ring. All calculations were run on personal computers belonging to the Medical Sciences University of Las Tunas, from November 2009 to March 2010. Results: The structural parameters of the beta-lactam ring do not change as a result of changes in the side chains. The ring has a marked tendency to planarity. The ceftobiprole is different from the rest of the cephalosporins in the spatial disposition of the side chain, which facilitates access to the carbonyl carbon. There are no significant variations in the charge densities, especially in the positive charge of this carbon. Conclusions: The structure and electronic properties of the beta-lactam ring have no significant changes among modeled cephalosporins. The three dimensional structure of ceftobiprole favors a higher reactivity.
Fisenko, Anatoliy I
2014-01-01
Use formulas to describe the monopole and dipole spectra of the Cosmic Microwave Background (CMB) radiation, the exact expressions for the temperature dependences of the radiative and thermodynamic functions, such as the total radiation power per unit area, total energy density, number density of photons, Helmholtz free energy density, entropy density, heat capacity at constant volume, pressure, enthalpy density, and internal energy density in the finite range of frequencies are obtained. Since the dependence of temperature upon the redshift z is known, the obtained expressions can be simply presented in z representation. Utilizing experimental data for the monopole and dipole spectra measured by the COBE FIRAS instrument in the 60 - 600 GHz frequency interval at the temperature T = 2.728 K, the values of the radiative and thermodynamic functions, as well as the radiation density constant a and the Stefan-Boltzmann constant are calculated. In the case of the dipole spectrum, the constants a and the Stefan-Bol...
Kerns, James R; Stingo, Francesco; Followill, David S; Howell, Rebecca M; Melancon, Adam; Kry, Stephen F
2017-08-01
The anthropomorphic phantom program at the Houston branch of the Imaging and Radiation Oncology Core (IROC-Houston) is an end-to-end test that can be used to determine whether an institution can accurately model, calculate, and deliver an intensity modulated radiation therapy dose distribution. Currently, institutions that do not meet IROC-Houston's criteria have no specific information with which to identify and correct problems. In the present study, an independent recalculation system was developed to identify treatment planning system (TPS) calculation errors. A recalculation system was commissioned and customized using IROC-Houston measurement reference dosimetry data for common linear accelerator classes. Using this system, 259 head and neck phantom irradiations were recalculated. Both the recalculation and the institution's TPS calculation were compared with the delivered dose that was measured. In cases in which the recalculation was statistically more accurate by 2% on average or 3% at a single measurement location than was the institution's TPS, the irradiation was flagged as having a "considerable" institutional calculation error. The error rates were also examined according to the linear accelerator vendor and delivery technique. Surprisingly, on average, the reference recalculation system had better accuracy than the institution's TPS. Considerable TPS errors were found in 17% (n=45) of the head and neck irradiations. Also, 68% (n=13) of the irradiations that failed to meet the IROC-Houston criteria were found to have calculation errors. Nearly 1 in 5 institutions were found to have TPS errors in their intensity modulated radiation therapy calculations, highlighting the need for careful beam modeling and calculation in the TPS. An independent recalculation system can help identify the presence of TPS errors and pass on the knowledge to the institution. Copyright © 2017 Elsevier Inc. All rights reserved.
GLYCOLIC ACID PHYSICAL PROPERTIES, IMPURITIES, AND RADIATION EFFECTS ASSESSMENT
Energy Technology Data Exchange (ETDEWEB)
Lambert, D.; Pickenheim, B.; Hay, M.
2011-06-20
The Defense Waste Processing Facility (DWPF) is pursuing alternative reductants/flowsheets to increase attainment to meet closure commitment dates. In fiscal year 2009, SRNL evaluated several options and recommended the further assessment of the nitric/formic/glycolic acid flowsheet. SRNL is currently performing testing with this flowsheet to support the DWPF down-select of alternate reductants. As part of the evaluation, SRNL was requested to determine the physical properties of formic and glycolic acid blends. Blends of formic acid in glycolic acid were prepared and their physical properties tested. Increasing amounts of glycolic acid led to increases in blend density, viscosity and surface tension as compared to the 90 wt% formic acid that is currently used at DWPF. These increases are small, however, and are not expected to present any difficulties in terms of processing. The effect of sulfur impurities in technical grade glycolic acid was studied for its impact on DWPF glass quality. While the glycolic acid specification allows for more sulfate than the current formic acid specification, the ultimate impact is expected to be on the order of 0.03 wt% sulfur in glass. Note that lower sulfur content glycolic acid could likely be procured at some increased cost if deemed necessary. A paper study on the effects of radiation on glycolic acid was performed. The analysis indicates that substitution of glycolic acid for formic acid would not increase the radiolytic production rate of H{sub 2} and cause an adverse effect in the SRAT or SME process. It has been cited that glycolic acid solutions that are depleted of O{sub 2} when subjected to large radiation doses produced considerable quantities of a non-diffusive polymeric material. Considering a constant air purge is maintained in the SRAT and the solution is continuously mixed, oxygen depletion seems unlikely, however, if this polymer is formed in the SRAT solution, the rheology of the solution may be affected and
Simplifying the calculation of light scattering properties for black carbon fractal aggregates
Smith, A. J. A.; Grainger, R. G.
2014-02-01
Black carbon fractal aggregates have complicated shapes that make the calculation of their optical properties particularly computationally expensive. Here, a method is presented to estimate fractal aggregate light scattering properties by optimising simplified models to full light scattering calculations. It is found that there are no possible spherical models (at any size or refractive index) that well represent the light scattering in the visible, or near-thermal infrared. As such, parameterisations of the light scattering as a function of the number of aggregate particles is presented as the most pragmatic choice for modelling distributions of black carbon when the large computational overheads of rigorous scattering calculations cannot be justified. This parameterisation can be analytically integrated to provide light scattering properties for log-normal distributions of black carbon fractal aggregates and return extinction cross-sections with 0.1% accuracy for typical black carbon size distributions. Scattering cross-sections and the asymmetry parameter can be obtained to within 3%.
Simplifying the calculation of light scattering properties for black carbon fractal aggregates
Directory of Open Access Journals (Sweden)
A. J. A. Smith
2014-08-01
Full Text Available Black carbon fractal aggregates have complicated shapes that make the calculation of their optical properties particularly computationally expensive. Here, a method is presented to estimate fractal aggregate light scattering properties by optimising simplified models to full light scattering calculations. It is found that there are no possible spherical models (at any size or refractive index that well represent the light scattering in the visible or near-thermal infrared. As such, parameterisations of the light scattering as a function of the number of aggregate particles is presented as the most pragmatic choice for modelling distributions of black carbon when the large computational overheads of rigorous scattering calculations cannot be justified. This parameterisation can be analytically integrated to provide light scattering properties for lognormal distributions of black carbon fractal aggregates and return extinction cross sections with 0.1% accuracy for typical black carbon size distributions. Scattering cross sections and the asymmetry parameter can be obtained to within 3%.
Wentzcovitch, R. M.; Wu, Z.; Cococcioni, M.; Umemoto, K.
2012-12-01
First principles calculations in mineral physics have contributed decisively to understanding numerous mineral properties of interest in geophysics. Thermal elasticity is the essential property that allows for direct insights into the origin of seismic observables such as velocity discontinuities, gradients, anisotropies, and heterogeneities. Earth materials are challenging to calculations because they contain iron, a strongly correlated element that may undergo spin crossover under pressure, hydrogen, that even in very small amounts can produce can produce anelastic effects, and phases that are stabilized only by anharmonic fluctuations, e.g., CaSiO3-perovskite. I will describe recent progress in methodology that is enabling calculations of thermal elastic properties with unprecedented easiness. I will exemplify its power on iron bearing phases including some undergoing spin crossovers, and provide an updated view of lower mantle velocities.
Aarts, Ronald M; Janssen, Augustus J E M
2016-12-01
The Struve functions Hn(z), n=0, 1, ... are approximated in a simple, accurate form that is valid for all z≥0. The authors previously treated the case n = 1 that arises in impedance calculations for the rigid-piston circular radiator mounted in an infinite planar baffle [Aarts and Janssen, J. Acoust. Soc. Am. 113, 2635-2637 (2003)]. The more general Struve functions occur when other acoustical quantities and/or non-rigid pistons are considered. The key step in the paper just cited is to express H1(z) as (2/π)-J0(z)+(2/π) I(z), where J0 is the Bessel function of order zero and the first kind and I(z) is the Fourier cosine transform of [(1-t)/(1+t)](1/2), 0≤t≤1. The square-root function is optimally approximated by a linear function ĉt+d̂, 0≤t≤1, and the resulting approximated Fourier integral is readily computed explicitly in terms of sin z/z and (1-cos z)/z(2). The same approach has been used by Maurel, Pagneux, Barra, and Lund [Phys. Rev. B 75, 224112 (2007)] to approximate H0(z) for all z≥0. In the present paper, the square-root function is optimally approximated by a piecewise linear function consisting of two linear functions supported by [0,t̂0] and [t̂0,1] with t̂0 the optimal take-over point. It is shown that the optimal two-piece linear function is actually continuous at the take-over point, causing a reduction of the additional complexity in the resulting approximations of H0 and H1. Furthermore, this allows analytic computation of the optimal two-piece linear function. By using the two-piece instead of the one-piece linear approximation, the root mean square approximation error is reduced by roughly a factor of 3 while the maximum approximation error is reduced by a factor of 4.5 for H0 and of 2.6 for H1. Recursion relations satisfied by Struve functions, initialized with the approximations of H0 and H1, yield approximations for higher order Struve functions.
First-principles calculations on thermodynamic properties of BaTiO3 rhombohedral phase.
Bandura, Andrei V; Evarestov, Robert A
2012-07-05
The calculations based on the linear combination of atomic orbitals have been performed for the low-temperature phase of BaTiO(3) crystal. Structural and electronic properties, as well as phonon frequencies were obtained using hybrid PBE0 exchange-correlation functional. The calculated frequencies and total energies at different volumes have been used to determine the equation of state and thermal contribution to the Helmholtz free energy within the quasiharmonic approximation. For the first time, the bulk modulus, volume thermal expansion coefficient, heat capacity, and Grüneisen parameters in BaTiO(3) rhombohedral phase have been estimated at zero pressure and temperatures form 0 to 200 K, based on the results of first-principles calculations. Empirical equation has been proposed to reproduce the temperature dependence of the calculated quantities. The agreement between the theoretical and experimental thermodynamic properties was found to be satisfactory.
Jain, C.P.
2014-01-01
The effects of radiation on the structural and electrical properties of electronic devices are complex in nature and have changed much during decades of device evolution. These effects are mainly because of radiation induced charge build-up in oxide and interfacial regions. This paper presents a details of these radiation induced effects, their dependencies, and the change in structural properties and electrical characterises of different devices before and after irradiation are measured and ...
Directory of Open Access Journals (Sweden)
Hassan Maktuff Jaber Al-Ta'ii
2015-02-01
Full Text Available Many types of materials such as inorganic semiconductors have been employed as detectors for nuclear radiation, the importance of which has increased significantly due to recent nuclear catastrophes. Despite the many advantages of this type of materials, the ability to measure direct cellular or biological responses to radiation might improve detector sensitivity. In this context, semiconducting organic materials such as deoxyribonucleic acid or DNA have been studied in recent years. This was established by studying the varying electronic properties of DNA-metal or semiconductor junctions when exposed to radiation. In this work, we investigated the electronics of aluminium (Al/DNA/silicon (Si rectifying junctions using their current-voltage (I-V characteristics when exposed to alpha radiation. Diode parameters such as ideality factor, barrier height and series resistance were determined for different irradiation times. The observed results show significant changes with exposure time or total dosage received. An increased deviation from ideal diode conditions (7.2 to 18.0 was observed when they were bombarded with alpha particles for up to 40 min. Using the conventional technique, barrier height values were observed to generally increase after 2, 6, 10, 20 and 30 min of radiation. The same trend was seen in the values of the series resistance (0.5889–1.423 Ω for 2–8 min. These changes in the electronic properties of the DNA/Si junctions could therefore be utilized in the construction of sensitive alpha particle detectors.
A Simple Practical Method for Calculating the Calorimetric Properties of Combustion Gas
1980-01-01
The simplified formulae are proposed for the enthalpy and the entropy of combustion gas constituents, by treating each gas constituent as semi-ideal gas. Based on these formulae, there is shown the practical method for calculating directly the calorimetric properties of combustion gas and the adiabatic combustion temperature. This method allows one to analyse the heat processes of combustion gas within the error approvable for practical use and also with practical simplicity. Some calculated ...
Comptomization and radiation spectra of X-ray sources. Calculation of the Monte Carlo method
Pozdnyakov, L. A.; Sobol, I. M.; Sonyayev, R. A.
1980-01-01
The results of computations of the Comptomization of low frequency radiation in weakly relativistic plasma are presented. The influence of photoabsorption by iron ions on a hard X-ray spectrum is considered.
Battistel, O A
2001-01-01
We investigate the possibility of Lorentz and CPT violations in the photon sector, of the Chern-Simons form, be induced by radiative corrections arising from the Lorentz and CPT non-invariant fermionic sector of an extended version of QED. By analyzing the modified vacuum polarization tensor, three contributions are considered: two of them can be identified with well known amplitudes; the (identical) QED vacuum polarization tensor and the (closely related) $AVV$ triangular amplitude. These amplitudes are evaluated in their most general form (to include in our discussion automatically the question of ambiguities) on the point of view of a strategy to manipulate and calculate divergent amplitudes that can avoid the explicit calculation of divergent integrals. Rather than this only general properties are used in intermediary steps. With this treatment, the results obtained by others authors can be easily recovered and we show that, if we choose to impose U(1) gauge invariance maintenance in the pure QED calculat...
First-Principles Calculations for Thermodynamic Properties of Perovskite-Type Superconductor MgCNi
Institute of Scientific and Technical Information of China (English)
ZHANG Wei; LI Zhe; CHEN Xiang-Rong; CAI Ling-Cang; JING Fu-Qian
2008-01-01
The ground state properties and equation of state of the non-oxide perovskite-type superconductor MgCNi,3 are investigated by first-principles calculations based on the plane-wave basis set with the local density approximation (LDA) as well as the generalized gradient approximation (GGA) for exchange and correlation, which agree well with both theoretical calculations and experiments. Some thermodynamic properties including the heat capacity, the thermal expansion coefficient and the Gruneisen parameter for perovskite structure MgCNi,3 are obtained.
Theoretical Calculations of Refractive Properties for Hg3Te2Cl2 Crystals
Bokotey, O. V.
2016-05-01
This paper reviews the optical properties, such as refractive index, optical dielectric constant, and reflection coefficient of the Hg3Te2Cl2 crystals. The applications of the Hg3X2Y2 crystals as electronic, optical, and optoelectronic devices are very much determined by the nature and magnitude of these fundamental material properties. The origin of chemical bonding in the crystals is very important for definition of the physical and chemical properties. The main structural feature of the Hg3X2Y2 crystals is the presence of covalent pyramids [XHg3] and linear X-Hg-X groups. Optical properties are calculated according to the model proposed by Harrison. The refractive index in the spectral region far from the absorption edge is determined within the generalized single-oscillator model. The calculated results are found to be in good agreement with experimental data.
DEFF Research Database (Denmark)
Weitzmann, Peter; Svendsen, Svend
2005-01-01
Lightweight floor heating systems consist of a plastic tube connected to a heat distribution aluminium plate and are used in wooden floor constructions. The thermal properties of lightweight floor heating systems cannot be described accurately. The reason is a very complex interaction of convection......, radiation and conduction of the heat transfer between pipe and surrounding materials. The European Standard for floor heating, EN1264, does not cover lightweight systems, while the supplemental Nordtest Method VVS127 is aimed at lightweight systems. The thermal properties can be found using tabulated values...
Transverse coherence properties of X-ray beams in third-generation synchrotron radiation sources
Geloni, Gianluca; Schneidmiller, Evgeni; Yurkov, Mikhail
2008-01-01
This article describes a complete theory of spatial coherence for undulator radiation sources. Current estimations of coherence properties often assume that undulator sources are quasi-homogeneous, like thermal sources, and rely on the application of the van Cittert-Zernike theorem for calculating the degree of transverse coherence. Such assumption is not adequate when treating third generation light sources, because the vertical(geometrical) emittance of the electron beam is comparable or even much smaller than the radiation wavelength in a very wide spectral interval that spans over four orders of magnitude (from 0.1 Angstrom up to 10^3 Angstrom). Sometimes, the so-called Gaussian-Schell model, that is widely used in statistical optics in the description of partially-coherent sources, is applied as an alternative to the quasi-homogeneous model. However, as we will demonstrate, this model fails to properly describe coherent properties of X-ray beams from non-homogeneous undulator sources. As a result, a more...
Directory of Open Access Journals (Sweden)
E. K. Agakhanov
2016-01-01
Full Text Available The necessity of studying the effect impact of elementary particles impact on the strength and deformation materials properties used in protective constructions nuclear reactors and reactor technology has been stipulated. A nuclear reactor pressure vessel from prestressed concrete, combining the functions of biological protection is to be considered. The neutron flux problem distribution in the pressure vessel of a nuclear reactor has been solved. The solution is made in axisymmetric with the finite element method using a flat triangular finite element. Computing has been conducted in Matlab package. The comparison with the results has been obtained using the finite difference method, as well as the graphs of changes under the influence of radiation exposure and the elastic modulus of concrete radiation deformations have been constructed. The proposed method allows to simulate changes in the deformation properties of concrete under the influence of neutron irradiation. Results of the study can be used in the calculation of stress-strain state of structures, taking into account indirect heterogeneity caused by the physical fields influence.
Effect of magnetic polaritons on the radiative properties of inclined plate arrays
Wang, Liping; Haider, Ahmad; Zhang, Zhuomin
2014-01-01
This study investigates the spectral radiative properties of inclined parallel-plate arrays with emphasis on the effect of magnetic polaritons. The rigorous coupled-wave analysis (RCWA) is employed and the geometry of parallel-plate arrays is reproduced by considering the structure as a multilayered grating with lateral shift. Enhanced absorption at specific wavelengths with angular independence due to the excitation of magnetic resonances is demonstrated with the numerical calculation. The magnetic resonance condition can be simply predicted by a modified capacitor-inductor (LC) model, and electromagnetic field distributions are presented to illustrate the unique behavior of magnetic polaritons such as field localization and induced currents. The agreement between the RCWA and LC model on the resonance conditions confirms the excitation of magnetic polaritons. A parametric study is conducted to investigate the geometric effects on the radiative properties. It is shown that the resonance wavelengths of magnetic polaritons can be tuned by changing the plate length, thickness, period, or inclination angle. The understanding gained from this study may benefit the design of energy harvesting devices.
Huang, Yiyi; Dong, Xiquan; Xi, Baike; Dolinar, Erica K.; Stanfield, Ryan E.
2017-02-01
The most prominent September Arctic sea ice decline over the period of 2000-2015 occurs over the Siberian Sea, Laptev Sea, and Kara Sea. The satellite observed and retrieved sea ice concentration (SIC) and cloud/radiation properties over the Arctic (70°-90°N) have been used to investigate the impact of springtime cloud and radiation properties on September SIC variation. Positive trends of cloud fractions, cloud water paths, and surface downward longwave flux at the surface over the September sea ice retreat areas are found over the period of 1 March to 14 May, while negative trends are found over the period of 15 May to 28 June. The spatial distributions of correlations between springtime cloud/radiation properties and September SIC have been calculated, indicating that increasing cloud fractions and downward longwave flux during springtime tend to enhance sea ice melting due to strong cloud warming effect. Surface downward and upward shortwave fluxes play an important role from May to June when the onset of sea ice melting occurs. The comparison between linearly detrended and nondetrended of each parameter indicates that significant impact of cloud and radiation properties on September sea ice retreat occurs over the Chukchi/Beaufort Sea at interannual time scale, especially over the period of 31 March to 29 April, while strongest climatological trends are found over the Laptev/Siberian Sea.
Radiative properties of advanced spacecraft heat shield materials
Cunnington, G. R.; Funai, A. I.; Mcnab, T. K.
1983-01-01
Experimental results are presented to show the effects of simulated reentry exposure by convective heating and by radiant heating on spectral and total emittance of statically oxidized Inconel 617 and Haynes HS188 superalloys to 1260 K and a silicide coatea (R512E) columbium 752 alloy to 1590 K. Convective heating exposures were conducted in a supersonic arc plasma wind tunnel using a wedge-shaped specimen configuration. Radiant tests were conducted at a pressure of .003 atmospheres of dry air at a flow velocity of several meters per second. Convective heating specimens were subjected to 8, 20, and 38 15-min heating cycles, and radiant heating specimens were tested for 10, 20, 50, and 100 30-min heating cycles. Changes in radiative properties are explained in terms of changes in composition resulting from simulated reentry tests. The methods used to evaluate morphological, compositional and crystallographic changes include: Auger electron spectroscopy; scanning electron microscopy; X-ray diffraction analysis; and electron microprobe analysis.
Russell, Philip B.; Valero, F. P. J.; Flatau, P. J.; Bergin, M.; Holben, B.; Nakajima, T.; Pilewskie, P.; Bergstrom, R.; Hipskind, R. Stephen (Technical Monitor)
2001-01-01
depth gradient, with AOD(500 nm) extremes from 0.1 to 1.1. On the Pacific transit from Honolulu to Hachijo AOD(500 nm) averaged 0.2, including increases to 0.4 after several storms, suggesting the strong impact of wind-generated seasalt. The AOD maximum, found in the Sea of Japan, was influenced by dust and anthropogenic sources. (4) In Beijing, single scattering albedo retrieved from AERONET sun-sky radiometry yielded midvisible SSA=0.88 with strong wavelength dependence, suggesting a significant black carbon component. SSA retrieved during dust episodes was approx. 0.90 and variable but wavelength neutral reflecting the presence of urban haze with the dust. Downwind at Anmyon Island SSA was considerably higher, approx. 0.94, but wavelength neutral for dust episodes and spectrally dependent during non dust periods. (5) Satellite retrievals show major aerosol features moving from Asia over the Pacific; however, determining seasonal-average aerosol effects is hampered by sampling frequency and large-scale cloud systems that obscure key parts of aerosol patterns. Preliminary calculations using, satellite-retrieved AOD fields and initial ACE-Asia aerosol properties (including sulfates, soot, and dust) yield clear-sky aerosol radiative effects in the seasonal-average ACE-Asia plume exceeding those of manmade greenhouse gases. Quantifying all-sky direct aerosol radiative effects is complicated by the need to define the height of absorbing aerosols with respect to cloud decks.
Riis, Hans L; Moltke, Lars N; Zimmermann, Sune J; Ebert, Martin A; Rowshanfarzad, Pejman
2016-06-07
Accurate determination of the megavoltage (MV) radiation isocentre of a linear accelerator (linac) is an important task in radiotherapy. The localization of the MV radiation isocentre is crucial for correct calibration of the in-room lasers and the cone-beam CT scanner used for patient positioning prior to treatment. Linac manufacturers offer tools for MV radiation isocentre localization. As a user, there is no access to the documentation for the underlying method and calculation algorithm used in the commercial software. The idea of this work was to evaluate the accuracy of the software tool for MV radiation isocentre calculation as delivered by Elekta using independent software. The image acquisition was based on the scheme designed by the manufacturer. Eight MV images were acquired in each series of a ball-bearing (BB) phantom attached to the treatment couch. The images were recorded at cardinal angles of the gantry using the electronic portal imaging device (EPID). Eight Elekta linacs with three different types of multileaf collimators (MLCs) were included in the test. The influence of MLC orientation, x-ray energy, and phantom modifications were examined. The acquired images were analysed using the Elekta x-ray volume imaging (XVI) software and in-house developed (IHD) MATLAB code. Results from the two different software were compared. A discrepancy in the longitudinal direction of the isocentre localization was found averaging 0.23 mm up to a maximum of 0.75 mm. The MLC orientation or the phantom asymmetry in the longitudinal direction do not appear to cause the discrepancy. The main cause of the differences could not be clearly identified. However, it is our opinion that the commercial software delivered by the linac manufacturer should be improved to reach better stability and precise results in the MV radiation isocentre calculations.
Riis, Hans L.; Moltke, Lars N.; Zimmermann, Sune J.; Ebert, Martin A.; Rowshanfarzad, Pejman
2016-06-01
Accurate determination of the megavoltage (MV) radiation isocentre of a linear accelerator (linac) is an important task in radiotherapy. The localization of the MV radiation isocentre is crucial for correct calibration of the in-room lasers and the cone-beam CT scanner used for patient positioning prior to treatment. Linac manufacturers offer tools for MV radiation isocentre localization. As a user, there is no access to the documentation for the underlying method and calculation algorithm used in the commercial software. The idea of this work was to evaluate the accuracy of the software tool for MV radiation isocentre calculation as delivered by Elekta using independent software. The image acquisition was based on the scheme designed by the manufacturer. Eight MV images were acquired in each series of a ball-bearing (BB) phantom attached to the treatment couch. The images were recorded at cardinal angles of the gantry using the electronic portal imaging device (EPID). Eight Elekta linacs with three different types of multileaf collimators (MLCs) were included in the test. The influence of MLC orientation, x-ray energy, and phantom modifications were examined. The acquired images were analysed using the Elekta x-ray volume imaging (XVI) software and in-house developed (IHD) MATLAB code. Results from the two different software were compared. A discrepancy in the longitudinal direction of the isocentre localization was found averaging 0.23 mm up to a maximum of 0.75 mm. The MLC orientation or the phantom asymmetry in the longitudinal direction do not appear to cause the discrepancy. The main cause of the differences could not be clearly identified. However, it is our opinion that the commercial software delivered by the linac manufacturer should be improved to reach better stability and precise results in the MV radiation isocentre calculations.
Mancera, L; Takeuchi, N
2003-01-01
We have studied the structural and electronic properties of YN in rock salt (sodium chloride), caesium chloride, zinc blende and wurtzite structures using first-principles total energy calculations. Rock salt is the calculated ground state structure with a = 4.93 A, B sub 0 = 157 GPa. The experimental lattice constant is a = 4.877 A. There is an additional local minimum in the wurtzite structure with total energy 0.28 eV/unit cell higher. At high pressure (approx 138 GPa), our calculations predict a phase transformation from a NaCl to a CsCl structure.
Forecast of Piezoelectric Properties of Crystalline Materials from First Principle Calculation
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Piezo crystals including quartz, quartz-like crystals, known and novel crystals of langasite-type structure were treated with density-functional perturb theory (DFPT) using plane-wave pseudopotentials method, within the local density approximation (LDA) to the exchange-correlation functional. Compared with experimental results, the ab initio calculation results have quantitative or semi-quantitative accuracy. It is shown that first principle calculation opens a door to the search and design of new piezoelectric material. Further application of first principle calculation to forecast the whole piezoelectric properties was also discussed.
Macroscopic-microscopic calculations of ground state properties of superheavy nuclei
Institute of Scientific and Technical Information of China (English)
ZHI Qi-jun; Mao Ying-chen; REN Zhong-zhou
2006-01-01
We systematically calculate the ground state properties of superheavy even-even nuclei with proton number Z=94-118.The calculations are based on the liquid drop macroscopic model and the microscopic model with the modified single-particle oscillator potential. The calculated binding energies and α-decay energies agree well with the experimental data.The reliability of the macroscopic-microscopic(MM)model for superheavy nuclei is confirmed by the good agreement between calculated results and experimental ones. Detailed comparisons between our calculations and M(o)ller's are made.It is found that the calculated results also agree with M(o)ller's results and that the MM model is insensitive to the microscopic single-particle potential. Calculated results are also compared with results from relativistic mean-field (RMF)model and from Skyrme-Hatree-Fock(SHF) model.In addition,half-lives,deformations and shape coexistence are also investigated.The properties of some unknown nuclei are predicted and they will be useful for future experimental researches of superheavy nuclei.
Institute of Scientific and Technical Information of China (English)
Shen Tian-Ming; Chen Chong-Yang; Wang Yan-Sen
2007-01-01
In this paper a systematic study is carried out on the angular distribution and polarization of photons emitted following radiative recombination of H-like ions by a non-relativistic dipole approximation. In order to incorporate the screening effect due to inner-shell electrons, a distorted wave approach is used. The dependences of the calculated angular distribution and polarization on the reduced energy and nuclear charge are fitted by the corresponding empirical formulas respectively.
Energy Technology Data Exchange (ETDEWEB)
Abbas, Mahmoud I., E-mail: mabbas@physicist.net [Physics Department, Faculty of Science, Alexandria University, 21511 Alexandria (Egypt); Hammoud, Sami [Physics Department, Faculty of Science, Beirut Arab University, Beirut (Lebanon); Physics Department, Faculty of Science and Art, Lebanese International University (Lebanon); Ibrahim, Tarek; Sakr, Mohamed [Physics Department, Faculty of Science, Beirut Arab University, Beirut (Lebanon)
2015-01-21
In this article, we introduce a direct analytical mathematical method for calculating the solid angle, Ω, subtended at a point by closed elliptical contours. The solid angle is required in many areas of optical and nuclear physics to estimate the flux of particle beam of radiation and to determine the activity of a radioactive source. The validity of the derived analytical expressions was successfully confirmed by the comparison with some published data (Numerical Method)
Energy Technology Data Exchange (ETDEWEB)
Bogdanov, O.V., E-mail: bov@tpu.ru [Physics Faculty, Tomsk State University, Tomsk, 634050 (Russian Federation); Department of Higher Mathematics and Mathematical Physics, Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Kazinski, P.O., E-mail: kpo@phys.tsu.ru [Physics Faculty, Tomsk State University, Tomsk, 634050 (Russian Federation); Department of Higher Mathematics and Mathematical Physics, Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Lazarenko, G.Yu., E-mail: lazarenko.georgijj@icloud.com [Physics Faculty, Tomsk State University, Tomsk, 634050 (Russian Federation)
2017-05-15
The properties of radiation created by a classical ultrarelativistic scalar charged particle in a constant homogeneous crossed electromagnetic field are described both analytically and numerically with radiation reaction taken into account in the form of the Landau–Lifshitz equation. The total radiation naturally falls into two parts: the radiation formed at the entrance point of a particle into the crossed field (the synchrotron entrance radiation), and the radiation coming from the late-time asymptotics of a particle motion (the de-excited radiation). The synchrotron entrance radiation resembles, although does not coincide with, the ultrarelativistic limit of the synchrotron radiation: its distribution over energies and angles possesses almost the same properties. The de-excited radiation is soft, not concentrated in the plane of motion of a charged particle, and almost completely circularly polarized. The photon energy delivering the maximum to its spectral angular distribution decreases with increasing the initial energy of a charged particle, while the maximum value of this distribution remains the same at the fixed photon observation angle and entrance angle of a charged particle. The ultraviolet and infrared asymptotics of the total radiation are also described. - Highlights: • Properties of an electron radiation in a crossed electromagnetic field are studied. • Spectral angular distribution of the synchrotron entrance radiation is described. • Spectral angular distribution of the de-excited radiation is described. • De-excited radiation is almost completely circularly polarized. • Photon energy at the maximum of the de-excited radiation decreases with increasing the initial energy of an electron.
Delocalization error and "functional tuning" in Kohn-Sham calculations of molecular properties.
Autschbach, Jochen; Srebro, Monika
2014-08-19
Kohn-Sham theory (KST) is the "workhorse" of numerical quantum chemistry. This is particularly true for first-principles calculations of ground- and excited-state properties for larger systems, including electronic spectra, electronic dynamic and static linear and higher order response properties (including nonlinear optical (NLO) properties), conformational or dynamic averaging of spectra and response properties, or properties that are affected by the coupling of electron and nuclear motion. This Account explores the sometimes dramatic impact of the delocalization error (DE) and possible benefits from the use of long-range corrections (LC) and "tuning" of functionals in KST calculations of molecular ground-state and response properties. Tuning refers to a nonempirical molecule-specific determination of adjustable parameters in functionals to satisfy known exact conditions, for instance, that the energy of the highest occupied molecular orbital (HOMO) should be equal to the negative vertical ionization potential (IP) or that the energy as a function of fractional electron numbers should afford straight-line segments. The presentation is given from the viewpoint of a chemist interested in computations of a variety of molecular optical and spectroscopic properties and of a theoretician developing methods for computing such properties with KST. In recent years, the use of LC functionals, functional tuning, and quantifying the DE explicitly have provided valuable insight regarding the performance of KST for molecular properties. We discuss a number of different molecular properties, with examples from recent studies from our laboratory and related literature. The selected properties probe different aspects of molecular electronic structure. Electric field gradients and hyperfine coupling constants can be exquisitely sensitive to the DE because it affects the ground-state electron density and spin density distributions. For π-conjugated molecules, it is shown how the
Influence of x-ray radiation on the properties of magnetorheological elastomers
Yu, M.; Fu, J.; Ju, B. X.; Zheng, X.; Choi, S. B.
2013-12-01
In this work, the influence of x-ray radiation on the properties of magnetorheological elastomers (MREs) was experimentally investigated. Five MRE samples with the same composition were prepared, and then were irradiated by an x-ray detection machine, with different radiation doses. The microstructures of samples before and after x-ray irradiation were observed by using scanning electron microscopy. The dynamic mechanical properties of all samples were investigated under different magnetic flux densities. The experimental results indicated that the x-rays had a great impact on the properties of MRE. Due to the x-ray radiation, two kinds of radiation-induced effects were generated in the MRE, which were radiation-induced crosslinking and radiation-induced degradation. Based on the influence of the radiation-induced effects on MRE, the initial modulus of the MRE was increased by the radiation-induced crosslinking effect, but the MR effect of the MRE decreased. While the MRE began to degrade, the MR effect of the MRE exhibited a large increasing trend with the increase of the x-ray radiation dose. In addition, the damping property of the MRE was also influenced greatly by the x-ray radiation, and the loss factor of the MRE was increased dramatically first and then decreased under x-ray irradiation. On the basis of these results, this study may provide a good guideline for developing various applications of MREs.
Spectral properties of Compton inverse radiation: Application of Compton beams
Bulyak, Eugene
2013-01-01
Compton inverse radiation emitted due to backscattering of laser pulses off the relativistic electrons possesses high spectral density and high energy of photons - in hard x-ray up to gamma-ray energies - because of short wavelength of laser radiation as compared with the classical electromagnetic devices such as undulators. In this report, the possibility of such radiation to monochromatization by means of collimation is studied. Two approaches have been considered for the description of the spectral-angular density of Compton radiation based on the classical field theory and on the quantum electrodynamics. As is shown, both descriptions produce similar total spectra. On the contrary, angular distribution of the radiation is different: the classical approach predicted a more narrow radiation cone. Also proposed and estimated is a method of the `electronic' monochromatization based on the electronic subtraction of the two images produced by the electron beams with slightly different energies. A `proof-of-prin...
Piezoelectric, Mechanical and Acoustic Properties of KNaNbOF5 from First-Principles Calculations
Directory of Open Access Journals (Sweden)
Han Han
2015-12-01
Full Text Available Recently, a noncentrosymmetric crystal, KNaNbOF5, has attracted attention due to its potential to present piezoelectric properties. Although α- and β-KNaNbOF5 are similar in their stoichiometries, their structural frameworks, and their synthetic routes, the two phases exhibit very different properties. This paper presents, from first-principles calculations, comparative studies of the structural, electronic, piezoelectric, and elastic properties of the α and the β phase of the material. Based on the Christoffel equation, the slowness surface of the acoustic waves is obtained to describe its acoustic prosperities. These results may benefit further applications of KNaNbOF5.
DEFF Research Database (Denmark)
Fürst, Joachim Alexander; Hashemi, J.; Markussen, Troels
2009-01-01
techniques and tight-binding calculations to illustrate these materials' transmission properties and give physical arguments to interpret the numerical results. Specifically, above the Fermi energy we find a strong reduction in electron transmission due to localized states in certain regions of the structure......Fullerene functionalized carbon nanotubes-NanoBuds-form a novel class of hybrid carbon materials, which possesses many advantageous properties as compared to the pristine components. Here, we report a theoretical study of the electronic transport properties of these compounds. We use both ab initio...
Macroscopic Geo-Magnetic Radiation Model; Polarization effects and finite volume calculations
de Vries, Krijn D; Werner, Klaus
2010-01-01
An ultra-high-energy cosmic ray (UHECR) colliding with the Earth's atmosphere gives rise to an Extensive Air Shower (EAS). Due to different charge separation mechanisms within the thin shower front coherent electromagnetic radiation will be emitted within the radio frequency range. A small deviation of the index of refraction from unity will give rise to Cherenkov radiation up to distances of 100 meters from the shower core and therefore has to be included in a complete description of the radio emission from an EAS. Interference between the different radiation mechanisms, in combination with different polarization behavior will reflect in a lateral distribution function (LDF) depending on the orientation of the observer and a non-trivial fall-off of the radio signal as function of distance to the shower core.
Radiation Shielding Properties Comparison of Pb-Based Silicate, Borate, and Phosphate Glass Matrices
Directory of Open Access Journals (Sweden)
Suwimon Ruengsri
2014-01-01
Full Text Available Theoretical calculations of mass attenuation coefficients, partial interactions, atomic cross-section, and effective atomic numbers of PbO-based silicate, borate, and phosphate glass systems have been investigated at 662 keV. PbO-based silicate glass has been found with the highest total mass attenuation coefficient and then phosphate and borate glasses, respectively. Compton scattering has been the dominate interaction contributed to the different total attenuation coefficients in each of the glass matrices. The silicate and phosphate glass systems are more appropriate choices as lead-based radiation shielding glass than the borate glass system. Moreover, comparison of results has shown that the glasses possess better shielding properties than standard shielding concretes, suggesting a smaller size requirement in addition to transparency in the visible region.
Early radiative properties of the developments of time-symmetric conformally flat initial data
Energy Technology Data Exchange (ETDEWEB)
Kroon, Juan Antonio Valiente [Max Planck Institut fuer Gravitationsphysik, Albert Einstein Institut, Am Muehlenberg 1, 14476 Golm (Germany)
2003-03-07
Using a representation of spatial infinity based on the properties of conformal geodesics, the first terms of an expansion for the Bondi mass for the development of time-symmetric, conformally flat initial data are calculated. As is to be expected, the Bondi mass agrees with the ADM at the sets where null infinity 'touches' spatial infinity. The second term in the expansion is proportional to the sum of the squared norms of the Newman-Penrose constants of the spacetime. On the basis of this result it is argued that these constants may provide a measure of the incoming radiation contained in the spacetime. This is illustrated by means of the Misner and Brill-Lindquist datasets. (letter to the editor)
Energy Technology Data Exchange (ETDEWEB)
Denisov, O. B.; Orlov, N. Yu. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)
2011-09-15
The paper presents the results of theoretical and experimental studies of the radiative properties of plasmas produced by heating and compression of various materials to high energy densities. The specific features of the theoretical plasma model known as the ion model, which is used to calculate the radiative characteristics of plasmas of complex chemical composition, are discussed. The theoretical approach based on this model is applied to the plasma produced during the explosion of the X-pinch wires. The theoretical estimate of the radiation efficiency is compared with the experimental data on the total energy yield from an X-pinch made of two different wires (NiCr and Alloy 188). The radiative characteristics of (C12 H16 O8) and (C8 H12 O6) plasmas are calculated for the temperature diagnostics of plasmas produced from porous targets employed in inertial confinement fusion experiments with the use of laser radiation and heavy-ion beams.
First-Principles Calculation of the Optical Properties of an Amphiphilic Cyanine Dye Aggregate
Haverkort, Frank; Stradomska, Anna; Vries, Alex H. de; Knoester, Jasper
2014-01-01
Using a first-principles approach, we calculate electronic and optical properties of molecular aggregates of the dye amphi-pseudoisocyanine, whose structures we obtained from molecular dynamics (MD) simulations of the self-aggregation process. Using quantum chemistry methods, we translate the struct
Determination of properties for the calculation of aqueous thin film drying
Energy Technology Data Exchange (ETDEWEB)
Mintzlaff, J.
2001-09-01
This paper deals with the determination of various properties required for the numerical calculation of the thin film drying of a water based varnish applied on paper. Experimental and analytical methods which provide the activity of water in paper and in a water based varnish, and the diffusion coefficient of water in this varnish are presented. (orig.)
Perlov, A.; Chadov, S.; Ebert, H.; Chioncel, L.; Lichtenstein, A.I.; Katsnelson, M.I.
2004-01-01
An approach for the calculation of the optical and magneto-optical properties of solids based on the one-particle Green function is introduced in the framework of the linear muffin-tin orbital (LMTO) method. The approach keeps all advantages of the more accurate Korringa-Kohn-Rostoker (KKR) scheme a
Jensen, L; van Duijnen, PT; Snijders, JG
2003-01-01
A discrete solvent reaction field model for calculating frequency-dependent molecular linear response properties of molecules in solution is presented. The model combines a time-dependent density functional theory (QM) description of the solute molecule with a classical (MM) description of the discr
Directory of Open Access Journals (Sweden)
Crnomarković Nenad Đ.
2016-01-01
Full Text Available The influence of the number of gray gases in the weighted sum in the gray gases model on the calculation of the radiative heat transfer is discussed in the paper. A computer code which solved the set of equations of the mathematical model describing the reactive two-phase turbulent flow with radiative heat exchange and with thermal equilibrium between phases inside the pulverized coal-fired furnace was used. Gas-phase radiative properties were determined by the simple gray gas model and two combinations of the weighted sum of the gray gases models: one gray gas plus a clear gas and two gray gases plus a clear gas. Investigation was carried out for two values of the total extinction coefficient of the dispersed phase, for the clean furnace walls and furnace walls covered by an ash layer deposit, and for three levels of the approximation accuracy of the weighting coefficients. The influence of the number of gray gases was analyzed through the relative differences of the wall fluxes, wall temperatures, medium temperatures, and heat transfer rate through all furnace walls. The investigation showed that there were conditions of the numerical investigations for which the relative differences of the variables describing the radiative heat exchange decrease with the increase in the number of gray gases. The results of this investigation show that if the weighted sum of the gray gases model is used, the complexity of the computer code and calculation time can be reduced by optimizing the number of gray gases. [Projekat Ministarstva nauke Republike Srbije, br. TR-33018: Increase in energy and ecology efficiency of processes in pulverized coal-fired furnace and optimization of utility steam boiler air preheater by using in-house developed software tools
ALLDOS: a computer program for calculation of radiation doses from airborne and waterborne releases
Energy Technology Data Exchange (ETDEWEB)
Strenge, D.L.; Napier, B.A.; Peloquin, R.A.; Zimmerman, M.G.
1980-10-01
The computer code ALLDOS is described and instructions for its use are presented. ALLDOS generates tables of radiation doses to the maximum individual and the population in the region of the release site. Acute or chronic release of radionuclides may be considered to airborne and waterborne pathways. The code relies heavily on data files of dose conversion factors and environmental transport factors for generating the radiation doses. A source inventory data library may also be used to generate the release terms for each pathway. Codes available for preparation of the dose conversion factors are described and a complete sample problem is provided describing preparation of data files and execution of ALLDOS.
Bellotti, Enrico; Wen, Hanqing; Pinkie, Benjamin; Matsubara, Masahiko; Bertazzi, Francesco
2015-08-01
Understanding the radiative and non-radiative properties of semiconductor materials is a prerequisite for optimizing the performance of existing light emitters and detectors and for developing new device architectures based on novel materials. Due to the ever increasing complexity of novel semiconductor systems and their relative technological immaturity, it is essential to have design tools and simulation strategies that include the details of the microscopic physics and their dependence on the macroscopic (continuum) variables in the macroscopic device models. Towards this end, we have developed a robust full-band structure based approach that can be used to study the intrinsic material radiative and non-radiative properties and evaluate the same characteristics of low-dimensional device structures. A parallel effort is being carried out to model the effect of substrate driven stress/strain and material quality (dislocations and defects) on microscopic quantities such as non-radiative recombination rate. Using this modeling approach, we have extensively studied the radiative and non-radiative properties of both elemental (Si and Ge) and compound semiconductors (HgCdTe, InGaAs, InAsSb and InGaN). In this work we outline the details of the modelling approach, specifically the challenges and advantages related to the use of the full-band description of the material electronic structure. We will present a detailed comparison of the radiative and Auger recombination rates as a function of temperature and doping for HgCdTe and InAsSb that are two important materials for infrared detectors and emitters. Furthermore we will discuss the role of non-radiatiave Auger recombination processes in explaining the performance of light emitter diodes. Finally we will present the extension of the model to low dimensional structures employed in a number of light emitter and detector structures.
Elastic and Thermal Properties of Silicon Compounds from First-Principles Calculations
Hou, Haijun; Zhu, H. J.; Cheng, W. H.; Xie, L. H.
2016-07-01
The structural and elastic properties of V-Si (V3Si, VSi2, V5Si3, and V6Si5) compounds are studied by using first-principles method. The calculated equilibrium lattice parameters and formation enthalpy are in good agreement with the available experimental data and other theoretical results. The calculated results indicate that the V-Si compounds are mechanically stable. Elastic properties including bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are also obtained. The elastic anisotropies of V-Si compounds are investigated via the three-dimensional (3D) figures of directional dependences of reciprocals of Young's modulus. Finally, based on the quasi-harmonic Debye model, the internal energy, Helmholtz free energy, entropy, heat capacity, thermal expansion coefficient, Grüneisen parameter, and Debye temperature of V-Si compounds have been calculated.
First-principles calculations on elasticity and the thermodynamic properties of TaC under pressure
Energy Technology Data Exchange (ETDEWEB)
Peng, Feng; Han, Ligang; Fu, Hongzhi [College of Physics and Electronic Information, Luoyang Normal University, Luoyang (China); Cheng, Xinlu [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu (China)
2009-07-15
First-principles calculations on the elastic and the thermodynamic properties of TaC have been carried out with the plane-wave pseudopotential density functional method. The calculated values are in very good agreement with experimental data as well as with some of the existing model calculations. The dependence of the elastic constants c{sub ij}, the aggregate elastic moduli (B,G,E), and the elastic anisotropy on pressure have been investigated. Moreover, the variation of the Poisson ratio and Debye temperature with pressure have been investigated for the first time. Through the quasi-harmonic Debye model, the thermodynamic properties were also obtained successfully. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Elastic and thermal properties of silicon compounds from first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Hou, Haijun; Zhu, H.J. [Yancheng Institute of Technology (China). School of Materials Engineering; Cheng, W.H. [Yancheng Institute of Technology (China). Dept. of Light Chemical Engineering; Xie, L.H. [Sichuan Normal Univ., Chengdu (China). Inst. of Solid State Physics and School of Physics and Electronic Engineering
2016-11-01
The structural and elastic properties of V-Si (V{sub 3}Si, VSi{sub 2}, V{sub 5}Si{sub 3}, and V{sub 6}Si{sub 5}) compounds are studied by using first-principles method. The calculated equilibrium lattice parameters and formation enthalpy are in good agreement with the available experimental data and other theoretical results. The calculated results indicate that the V-Si compounds are mechanically stable. Elastic properties including bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are also obtained. The elastic anisotropies of V-Si compounds are investigated via the three-dimensional (3D) figures of directional dependences of reciprocals of Young's modulus. Finally, based on the quasi-harmonic Debye model, the internal energy, Helmholtz free energy, entropy, heat capacity, thermal expansion coefficient, Grueneisen parameter, and Debye temperature of V-Si compounds have been calculated.
First-Principles Calculations of Elastic and Thermal Properties of Molybdenum Disilicide
Institute of Scientific and Technical Information of China (English)
ZHU Zun-Lue; FU Hong-Zhi; SUN Jin-Feng; LIU Yu-Fang; SHI De-Heng; XU Guo-Liang
2009-01-01
The first-principles plane-wave pseudopotential method using the generalized gradient approximation within the framework of density functional theory is applied to anaylse the equilibrium lattice parameters,six independent elastic constants,bulk moduli,thermal expansions and heat capacities of MoSi2.The quasi-harmonic Debye model,using a set of total energy versus cell volume obtained with the plane-wave pseudopotential method,is applied to the study of the elastic properties,thermodynamic properties and vibrational effects.The calculated zero pressure elastic constants are in overall good agreement with the experimental data.The calculated heat capacities and the thermal expansions agree well with the observed values under ambient conditions and those calculated by others.The results show that the temperature has hardly any effect under high pressure.
LDA+ U calculation of structural and thermodynamic properties of Ce2O3
Zhu, Bo; Cheng, Yan; Niu, Zhen-Wei; Zhou, Meng; Gong, Min
2014-08-01
We investigated the structure and thermodynamic properties of the hexagonal Ce2O3 by using LDA+ U scheme in the frame of density functional theory (DFT), together with the quasi-harmonic Debye model. The obtained lattice constants, bulk modulus, and the insulating gap agree well with the available experimental data. We successfully yielded the temperature dependence of bulk modulus, volume, thermal expansion coefficient, Debye temperature, specific heat as well as the entropy at different U values. It is found that the introduction of the U value cannot only correct the calculation of the structure but also improve the accurate description of the thermodynamic properties of Ce2O3. When U = 6 eV the calculated volume (538 Bohr3) at 300 K agrees well with the experimental value (536 Bohr3). The calculated entropy curve becomes more and more close to the experimental curve with the increasing U value.
Directory of Open Access Journals (Sweden)
S. Otto
2010-11-01
Full Text Available Realistic size equivalence and shape of Saharan mineral dust particles are derived from on in-situ particle, lidar and sun photometer measurements during SAMUM-1 in Morocco (19 May 2006, dealing with measured size- and altitude-resolved axis ratio distributions of assumed spheroidal model particles. The data were applied in optical property, radiative effect, forcing and heating effect simulations to quantify the realistic impact of particle non-sphericity. It turned out that volume-to-surface equivalent spheroids with prolate shape are most realistic: particle non-sphericity only slightly affects single scattering albedo and asymmetry parameter but may enhance extinction coefficient by up to 10%. At the bottom of the atmosphere (BOA the Saharan mineral dust always leads to a loss of solar radiation, while the sign of the forcing at the top of the atmosphere (TOA depends on surface albedo: solar cooling/warming over a mean ocean/land surface. In the thermal spectral range the dust inhibits the emission of radiation to space and warms the BOA. The most realistic case of particle non-sphericity causes changes of total (solar plus thermal forcing by 55/5% at the TOA over ocean/land and 15% at the BOA over both land and ocean and enhances total radiative heating within the dust plume by up to 20%. Large dust particles significantly contribute to all the radiative effects reported.
Internet calculations of thermodynamic properties of substances: Some problems and results
Ustyuzhanin, E. E.; Ochkov, V. F.; Shishakov, V. V.; Rykov, S. V.
2016-11-01
Internet resources (databases, web sites and others) on thermodynamic properties R = (p,T,s,...) of technologically important substances are analyzed. These databases put online by a number of organizations (the Joint Institute for High Temperatures of the Russian Academy of Sciences, Standartinform, the National Institute of Standards and Technology USA, the Institute for Thermal Physics of the Siberian Branch of the Russian Academy of Sciences, etc) are investigated. Software codes are elaborated in the work in forms of “client functions” those have such characteristics: (i) they are placed on a remote server, (ii) they serve as open interactive Internet resources. A client can use them for a calculation of R properties of substances. “Complex client functions” are considered. They are focused on sharing (i) software codes elaborated to design of power plants (PP) and (ii) client functions those can calculate R properties of working fluids for PP.
First-Principles Calculations of Elastic and Thermal Properties of Lanthanum Hexaboride
Institute of Scientific and Technical Information of China (English)
XU Guo-Liang; CHEN Jing-Dong; XIA Yao-Zheng; LIU Xue-Feng; LIU Yu-Fang; ZHANG Xian-Zhou
2009-01-01
The plane-wave pseudopotential method using the generalized gradient approximation within the framework of density functional theory is applied to anaylse the bulk modulus, thermal expansion coefficient and heat capacity of LAB6. The quasi-harmonic Debye model, using a set of total energy versus volume obtained with the plane-wave pseudopotential method, is applied to the study of the thermal properties and vibrational effects. We analyse the bulk modulus of LaB6 up to 150OK. The elastic properties calculations show that our system is mechanically stable. For the heat capacity and the thermal expansion, significant differences in properties are observed above 30OK. The calculated zero pressure bulk modulus is in good agreement with the experimentai data. Moreover,the Debye temperatures are determined from the non-equilibrium Gibbs functions and compared to available data.
SHARC, A Model for Calculating Atmospheric and Infrared Radiation Under Non-Equilibrium Conditions
1994-01-24
0 Is ’ I E U L b) U0 -cc ccI U . 1250 1350 1450 1550 FRIEQUENCY (cm-1) Figure 4. Quiescent Nighttime Limb Spectrum from the CIRRS-1A ExperimentO ...1974). 27. C.B. Ludwig, W. Malkmus, J.E. Reardon, and J.A. Thomson , Handbook of Infrared Radiation From Combustion Gases, SP-3080, Scientific and
Energy Technology Data Exchange (ETDEWEB)
Frankel, J.I.
1997-09-01
This investigation used sysmbolic manipulation in developing analytical methods and general computational strategies for solving both linear and nonlinear, regular and singular integral and integro-differential equations which appear in radiative and mixed-mode energy transport. Contained in this report are seven papers which present the technical results as individual modules.
Macroscopic geo-magnetic radiation model; polarization effects and finite volume calculations
de Vries, Krijn D.; Scholten, Olaf; Werner, Klaus
2012-01-01
An ultra-high-energy cosmic ray (UHECR) colliding with the Earth's atmosphere gives rise to an Extensive Air Shower (EAS). Due to different charge separation mechanisms within the thin shower front coherent electromagnetic radiation will be emitted within the radio frequency range. A small deviation
Optical characterization of OLED emitter properties by radiation pattern analyses
Energy Technology Data Exchange (ETDEWEB)
Flaemmich, Michael
2011-09-08
Researches in both, academia and industry are investigating optical loss channels in OLED layered systems by means of optical simulation tools in order to derive promising concepts for a further enhancement of the overall device performance. Besides other factors, the prospects of success of such optimization strategies rely severely on the credibility of the optical input data. The present thesis provides a guideline to measure the active optical properties of OLED emitter materials in situ by radiation pattern analyses. Reliable and widely applicable methods are introduced to determine the internal electroluminescence spectrum, the profile of the emission zone, the dipole emitter orientation, and the internal luminescence quantum efficiency of emissive materials from the optical far field emission of OLEDs in electrical operation. The proposed characterization procedures are applied to sets of OLEDs containing both, fluorescent polymeric materials as well as phosphorescent small-molecular emitters, respectively. On the one hand, quite expected results are obtained. On the other hand, several novel and truly surprising results are found. Most importantly, this thesis contains the first report of a non-isotropic, mainly parallel emitter orientation in a phosphorescent small-molecular guest-host system (Ir(MDQ)2(acac) in a-NPD). Due to the latter result, emitter orientation based optimization of phosphorescent OLEDs seems to be within reach. Since parallel dipoles emit preferably into air, the utilization of smart emissive materials with advantageous molecular orientation is capable to boost the efficiency of phosphorescent OLEDs by 50%. Materials design, the influence of the matrix material and the substrate, as well as film deposition conditions are just a few parameters that need to be studied further in order to exploit the huge potential of the dipole emitter orientation in phosphorescent OLEDs.
First-principles calculations atomic structure and elastic properties of Ti-Nb alloys
Timoshevskii, A N; Ivasishin, O M
2011-01-01
Elastic properties of Ti based \\beta-alloy were studied by the method of the model structure first principle calculations. Concentrational dependence of Young modulus for the binary \\beta-alloy Ti-Nb was discovered. It is shown that peculiarities visible at 15-18% concentrations can be related to the different Nb atoms distribution. Detailed comparison of the calculation results with the measurement results was done. Young modulus for the set of the ordered structures with different Nb atoms location, which simulate triple \\beta-alloys Ti-29.7%Zr-18.5%Nb and Ti-51.8%Zr-18.5%Nb have been calculated. The results of these calculations allowed us to suggest the concentration region for single-phase ternary \\beta-phase alloys possessing low values of Young's modulus.
Calculated Changes in the Elastic Properties of MgCNi3 at the Superconducting Transition
Directory of Open Access Journals (Sweden)
R. Abd-Shukor
2013-01-01
Full Text Available We calculated the elastic properties of MgCNi3 at the superconducting transition ( using various thermodynamic and acoustic data. From the calculations, a step discontinuity of 8 ppm in the bulk modulus, 7 ppm in the Young’s modulus, and 3 ppm in the longitudinal sound velocity ( is expected at . The step discontinuities at the transition temperature indicated the importance of lattice changes to the superconducting mechanism of MgCNi3. The Debye temperature was calculated to be 460 K. The electron-phonon coupling constants calculated in the weak and strong coupling limits of the BCS theory and the van Hove scenario showed that MgCNi3 is a moderately strong coupled superconductor.
Energy Technology Data Exchange (ETDEWEB)
Baldacci, F.; Delaire, F.; Letang, J.M.; Sarrut, D.; Smekens, F.; Freud, N. [Lyon-1 Univ. - CREATIS, CNRS UMR5220, Inserm U1044, INSA-Lyon, Centre Leon Berard (France); Mittone, A.; Coan, P. [LMU Munich (Germany). Dept. of Physics; LMU Munich (Germany). Faculty of Medicine; Bravin, A.; Ferrero, C. [European Synchrotron Radiation Facility, Grenoble (France); Gasilov, S. [LMU Munich (Germany). Dept. of Physics
2015-05-01
The track length estimator (TLE) method, an 'on-the-fly' fluence tally in Monte Carlo (MC) simulations, recently implemented in GATE 6.2, is known as a powerful tool to accelerate dose calculations in the domain of low-energy X-ray irradiations using the kerma approximation. Overall efficiency gains of the TLE with respect to analogous MC were reported in the literature for regions of interest in various applications (photon beam radiation therapy, X-ray imaging). The behaviour of the TLE method in terms of statistical properties, dose deposition patterns, and computational efficiency compared to analogous MC simulations was investigated. The statistical properties of the dose deposition were first assessed. Derivations of the variance reduction factor of TLE versus analogous MC were carried out, starting from the expression of the dose estimate variance in the TLE and analogous MC schemes. Two test cases were chosen to benchmark the TLE performance in comparison with analogous MC: (i) a small animal irradiation under stereotactic synchrotron radiation therapy conditions and (ii) the irradiation of a human pelvis during a cone beam computed tomography acquisition. Dose distribution patterns and efficiency gain maps were analysed. The efficiency gain exhibits strong variations within a given irradiation case, depending on the geometrical (voxel size, ballistics) and physical (material and beam properties) parameters on the voxel scale. Typical values lie between 10 and 103, with lower levels in dense regions (bone) outside the irradiated channels (scattered dose only), and higher levels in soft tissues directly exposed to the beams.
Li, Zheng; Wang, Junhong; Duan, Jianjie; Zhang, Zhan; Chen, Meie
2016-03-18
In this paper the radiation property of the one-dimensional periodic leaky-wave structure is analysed using a new hybrid method, which involves the mode expansion method for expanding the periodic aperture field in terms of spatial harmonics and the method of effective radiation sections for transforming the expanded fields into far fields. Using this method, the radiation of each spatial harmonic can be achieved, and the contributions of the harmonics (especially the bounded modes) to the total radiation of the periodic leaky-wave structure can be calculated. The main findings in this paper demonstrate that the bounded modes in a finite length structure have obvious contribution to the far-field radiation, which was considered to be non-radiative and always ignored in the conventional researches.
Energy Technology Data Exchange (ETDEWEB)
Rhee, I. H.; Cho, D.; Youn, S. H.; Kim, H. S.; Lee, S. J.; Ahn, H. K. [Soonchunhyang University, Ahsan (Korea)
2002-04-01
This research is to develop a standard methodology for determining the input parameters that impose a substantial impact on radiation doses of residential individuals in the vicinity of four nuclear power plants in Korea. We have selected critical nuclei, pathways and organs related to the human exposure via simulated estimation with K-DOSE 60 based on the updated ICRP-60 and sensitivity analyses. From the results, we found that 1) the critical nuclides were found to be {sup 3}H, {sup 133}Xe, {sup 60}Co for Kori plants and {sup 14}C, {sup 41}Ar for Wolsong plants. The most critical pathway was 'vegetable intake' for adults and 'milk intake' for infants. However, there was no preference in the effective organs, and 2) sensitivity analyses showed that the chemical composition in a nuclide much more influenced upon the radiation dose than any other input parameters such as food intake, radiation discharge, and transfer/concentration coefficients by more than 102 factor. The effect of transfer/concentration coefficients on the radiation dose was negligible. All input parameters showed highly estimated correlation with the radiation dose, approximated to 1.0, except for food intake in Wolsong power plant (partial correlation coefficient (PCC)=0.877). Consequently, we suggest that a prediction model or scenarios for food intake reflecting the current living trend and a formal publications including details of chemical components in the critical nuclei from each plant are needed. Also, standardized domestic values of the parameters used in the calculation must replace the values of the existed or default-set imported factors via properly designed experiments and/or modelling such as transport of liquid discharge in waters nearby the plants, exposure tests on corps and plants so on. 4 figs., 576 tabs. (Author)
A new parameterization for ice cloud optical properties used in BCC-RAD and its radiative impact
Zhang, Hua; Chen, Qi; Xie, Bing
2015-01-01
A new parameterization of the solar and infrared optical properties of ice clouds that considers the multiple habits of ice particles was developed on the basis of a prescribed dataset. First, the fitting formulae of the bulk extinction coefficient, single-scatter albedo, asymmetry factor, and δ-function forward-peak factor at the given 65 wavelengths as a function of effective radius were created for common scenarios, which consider a greater number of wavelengths and are more accurate than those used previously. Then, the band-averaged volume extinction and absorption coefficients, asymmetry factor and forward-peak factor of ice cloud were derived for the BCC-RAD (Beijing Climate Center radiative transfer model) using a parameter reference table. Finally, the newly developed and the original schemes in the BCC-RAD and the commonly used Fu Scheme of ice cloud were all applied to the BCC-RAD. Their influences on radiation calculations were compared using the mid-latitude summer atmospheric profile with ice clouds under no-aerosol conditions, and produced a maximum difference of approximately 30.0 W/m2 for the radiative flux, and 4.0 K/d for the heating rate. Additionally, a sensitivity test was performed to investigate the impact of the ice crystal density on radiation calculations using the three schemes. The results showed that the maximum difference was 68.1 W/m2 for the shortwave downward radiative flux (for the case of perpendicular solar insolation), and 4.2 K/d for the longwave heating rate, indicating that the ice crystal density exerts a significant effect on radiation calculations for a cloudy atmosphere.
Ab-initio calculations of electronic structure and optical properties of TiAl alloy
Hussain, Altaf; Sikandar Hayat, Sardar; Choudhry, M. A.
2011-05-01
The electronic structures and optical properties of TiAl intermetallic alloy system are studied by the first-principle orthogonalized linear combination of atomic orbitals method. Results on the band structure, total and partial density of states, localization index, effective atomic charges, and optical conductivity are presented and discussed in detail. Total density of states spectra reveal that (near the Fermi level) the majority of the contribution is from Ti-3d states. The effective charge calculations show an average charge transfer of 0.52 electrons from Ti to Al in primitive cell calculations of TiAl alloy. On the other hand, calculations using supercell approach reveal an average charge transfer of 0.48 electrons from Ti to Al. The localization index calculations, of primitive cell as well as of supercell, show the presence of relatively localized states even above the Fermi level for this alloy. The calculated optical conductivity spectra of TiAl alloy are rich in structures, showing the highest peak at 5.73 eV for supercell calculations. Calculations of the imaginary part of the linear dielectric function show a prominent peak at 5.71 eV and a plateau in the range 1.1-3.5 eV.
Physical Properties of Phenol Compound: Semi-empirical Calculation of Substituent Effects [Part One
Directory of Open Access Journals (Sweden)
Ammar A. Ibrahim
2009-01-01
Full Text Available Problem statement: Physical properties of phenol compound such as steric energy, charge of oxygen, ionization potential, dipole moment, LUMO and bond length have been calculated. Approach: All molecular geometries were minimized by quantum mechanic especially at (AM1 method was used to investigate the effect of a variety of substituents on the phenol (H, o-Cl, p-Cl, m-Cl, o-CH3, m-CH3, p-CH3, o-NH2, m-NH2, o-NO2, m-NO2, p-NO2, 2,4-di-NO2. Global descriptor such as electronic chemical potential (µ, hardness (η, the maximum electronic charge and global electrophilicity index (ω were determined and used to predict the (pKa values. Results: The theoretical results (predictive values found were in good agreement with experimental values. The predictive pKa calculated values by AM1 method gave excellent results with experimental values. The correlation between the predicted values especially global electrophilicity index showed excellent qualitative agreement with the experimental pKa (R2 = 0.95. Conclusion: The present research was to calculate the physical properties of phenol derivatives. Then, the calculated values were compared, quite favorably with experimental values of these properties. In future, we can predict any substituent of set of a phenol compound and compare its value with the experimental.
Influence of radiation damage on BGO scintillation properties
Energy Technology Data Exchange (ETDEWEB)
Georgii, R.; Meissl, R.; Lichti, G.G.; Schoenfelder, V. [Max-Planck-Institut fuer Extraterrestrische Physik, Garching (Germany); Hajdas, W. [Paul-Scherrer Institut, CH-5232 Villigen (Switzerland); Henschel, H. [Fraunhofer-Institut fuer Naturwissenschaftlich-Technische Trendanalyse, D-53879 Euskirchen (Germany); Graef, H.-D.; Neumann-Cosel, P. von; Richter, A. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany)
1998-08-11
Aboard INTEGRAL, the next medium-size {gamma}-ray mission of the European Space Agency (ESA), a high-resolution Ge-spectrometer array with a BGO anticoincidence shield and imaging capability will be flown. The influence of the radiation damage on the photoelectron yield of the BGO scintillators due to the radiation environment in the orbit, i.e. {gamma}-rays, electrons and protons from the radiation, belts and the cosmic diffuse radiation, was investigated. Irradiation tests with doses equivalent to the orbit conditions were performed and the photoelectron yields of different BGO crystals were measured. It was found that for equal doses the reduction of the photoelectron yield varies strongly for the crystals of different manufacturers. Furthermore, electromagnetic radiation affects the photoelectron yield much stronger than particle radiation. A possible explanation is given by interpreting the effect due to {gamma}-rays primarily as damage of the electronic structure of the BGO, whereas the particle radiation damages mainly the crystal structure. (orig.) 19 refs.
Energy Technology Data Exchange (ETDEWEB)
Pettengill, H.L. [USDOE, Washington, DC (United States); Soldat, J.K.; Swinth, K.L. [Pacific Northwest Lab., Richland, WA (United States)
1994-06-01
Most Manhattan District (MD) and Atomic Energy Commission (AEC) sites began environmental monitoring programs in the earliest years of their operation. The results were used to establish trends and to monitor for effluent releases that might be otherwise undetected. Very few data concerning radiation doses to the public in the vicinity of the sites were generated prior to 1960. Authoritative guidelines for controlling doses to the public were issued by national and international bodies beginning in the 1950s. In 1957, the Hanford Site began calculating and reporting maximum potential radiation doses to the public from several environmental pathways of exposure. Shortly thereafter, most AEC sites began programs aimed at either determining public doses, or ensuring that the doses were below the regulatory limits. Calculations of radiation doses to Maximally Exposed Individuals (MEI) at the Hanford Site have been recently completed by the Hanford Environmental Dose Reconstruction (HEDR) project. Collective doses for the public at Hanford were generated for this paper by utilizing the data developed by HEDR and approximate demographic data.
Electronic and optical properties of AlN under pressure: DFT calculations
Javaheri, Sahar; Boochani, Arash; Babaeipour, Manuchehr; Naderi, Sirvan
2017-01-01
Structural, elastic, optical, and electronic properties of wurtzite (WZ), zinc-blende (ZB), and rocksalt (RS) structures of AlN are investigated using the first-principles method and within the framework of density functional theory (DFT). Lattice parameters, bulk modulus, shear modulus, Young’s modulus, and elastic constants are calculated at zero pressure and compared with other experimental and theoretical results. The wurtzite and zinc-blende structures have a transition to rocksalt phase at the pressures of 12.7 GPa and 14 GPa, respectively. The electronic properties are calculated using both GGA and EV-GGA approximations; the obtained results by EV-GGA approximation are in much better agreement with the available experimental data. The RS phase has the largest bandgap with an amount of 4.98 eV; by increasing pressure, this amount is also increased. The optical properties like dielectric function, energy loss function, refractive index, and extinction coefficient are calculated under pressure using GGA approximation. Inter-band transitions are investigated using the peaks of imaginary part of the dielectric function and these transitions mainly occur from N-2p to Al-3p levels. The results show that the RS structure has more different properties than the WZ and ZB structures.
Directory of Open Access Journals (Sweden)
Afshin Akbarzadeh
2009-06-01
Full Text Available Introduction: One of the most important parameters in x-ray CT imaging is the noise induced by detected scattered radiation. The detected scattered radiation is completely dependent on the scanner geometry as well as size, shape and material of the scanned object. The magnitude and spatial distribution of the scattered radiation in x-ray CT should be quantified for development of robust scatter correction techniques. Empirical methods based on blocking the primary photons in a small region are not able to extract scatter in all elements of the detector array while the scatter profile is required for a scatter correction procedure. In this study, we measured scatter profiles in 64 slice CT scanners using a new experimental measurement. Material and Methods: To measure the scatter profile, a lead block array was inserted under the collimator and the phantom was exposed at the isocenter. The raw data file, which contained detector array readouts, was transferred to a PC and was read using a dedicated GUI running under MatLab 7.5. The scatter profile was extracted by interpolating the shadowed area. Results: The scatter and SPR profiles were measured. Increasing the tube voltage from 80 to 140 kVp resulted in an 80% fall off in SPR for a water phantom (d=210 mm and 86% for a polypropylene phantom (d = 350 mm. Increasing the air gap to 20.9 cm caused a 30% decrease in SPR. Conclusion: In this study, we presented a novel approach for measurement of scattered radiation distribution and SPR in a CT scanner with 64-slice capability using a lead block array. The method can also be used on other multi-slice CT scanners. The proposed technique can accurately estimate scatter profiles. It is relatively straightforward, easy to use, and can be used for any related measurement.
Xu, C.; Li, Q.; Liu, C. M.; Duan, M. Y.; Wang, H. K.
2016-05-01
First-principles calculations are employed to investigate the structural and elastic properties, formation enthalpies and chemical bonding features as well as hardness values of chromium tetraboride (CrB4) with different structures. The lattice parameters, Poisson’s ratio and B/G ratio are also derived. Our calculations indicate that the orthorhombic structure with Pnnm symmetry is the most energetically stable one for CrB4. Except for WB4P63/mmc structure with imaginary frequencies, another six new structures are investigated through the full phonon dispersion calculations. Their mechanical and thermodynamic stabilities are also studied by calculating the elastic constants and formation enthalpies. Our calculations show that the thermodynamic stabilities of all these CrB4 phases can be enhanced under high pressure. The large shear moduli, Young’s moduli and hardness values indicate that these CrB4 phases are potential hard materials. Analyses of the densities of states (DOSs) and electron localization functions (ELFs) provide further understandings of the chemical and physical properties of these CrB4 phases. It is observed that the large occupations and high strengths of the B-B covalent bonds are important for the stabilities, incompressibility and hardnesses of these CrB4 phases.
Garrido, Jorge; Wang, Wujun; Nilsson, Martin; Laumert, Björn
2016-05-01
A detailed 3-D radiation analysis of a dish-Stirling cavity receiver is carried out to estimate the cavity steady-state temperatures in order to assess the receiver integrity, lifetime and efficiency performance. For this purpose, a parabolic dish was modeled with 5.2 m focal length, 8.85 m aperture diameter and 2 mrad surface error. Three generic cavity shapes (cylindrical, diamond-shaped and reverse-conical) with three different emissivities (0.2, 0.4 and 0.7) are studied. Worst-case scenario heat generations (total absorbed radiation), maximum steady-state temperatures and energy balances of the cavities are calculated to evaluate the receiver performance. The results show that reverse-conical cavities can significantly reduce cavity wall peak temperatures (by 40-120 K), improve the temperature evenness and decrease the radiation losses by 4-5%. Regarding radiation properties, low reflectivities present lower steady-state temperatures even for low/moderate direct solar fluxes. Due to the lower temperatures, lower total thermal losses are also expected.
First-principles calculations of magnetic properties for CdCrO{sub 2} under pressure
Energy Technology Data Exchange (ETDEWEB)
Amari, S., E-mail: siham_amari@yahoo.fr [Laboratoire de Modelisation et de Simulation en Sciences des Materiaux, Departement de Physique Universite Djillali Liabes, Faculte des sciences, Universite Djillali Liabes, BP 89 Sidi Bel Abbes 22000 (Algeria); Mecabih, S.; Abbar, B.; Bouhafs, B. [Laboratoire de Modelisation et de Simulation en Sciences des Materiaux, Departement de Physique Universite Djillali Liabes, Faculte des sciences, Universite Djillali Liabes, BP 89 Sidi Bel Abbes 22000 (Algeria)
2013-02-15
By employing the first-principles method of the full potential linear augmented plane waves plus the local orbitals (FP-L/APW+lo) within the generalized gradient approximation for the exchange and correlation potential, the structural, electronic, and magnetic properties of chalcopyrite compound CdCrO{sub 2} are investigated. In order to take into account the strong on-site Coulomb interaction, we also performed the generalized gradient approximation plus the Hubbard correlation terms. We systematically study how the exchange interactions and magnetic moments of CdCrO{sub 2} are affected by the different choice of U as well as the exchange correlation potential. We have also carried out the pressure effect on the magnetic properties. - Highlights: Black-Right-Pointing-Pointer The calculation of the exchange constants. Black-Right-Pointing-Pointer The pressure dependence of the magnetic properties. Black-Right-Pointing-Pointer The exchange correlation potential effect on the magnetic properties.
Energy Technology Data Exchange (ETDEWEB)
Cheng, Guang; Sun, Xin; Wang, Yuxin; Tay, See Leng; Gao, Wei
2017-01-01
A new inverse method was proposed to calculate the anisotropic elastic-plastic properties (flow stress) of thin electrodeposited Ag coating utilizing nanoindentation tests, previously reported inverse method for isotropic materials and three-dimensional (3-D) finite element analyses (FEA). Indentation depth was ~4% of coating thickness (~10 μm) to avoid substrate effect and different indentation responses were observed in the longitudinal (L) and the transverse (T) directions. The estimated elastic-plastic properties were obtained in the newly developed inverse method by matching the predicted indentation responses in the L and T directions with experimental measurements considering indentation size effect (ISE). The results were validated with tensile flow curves measured from free-standing (FS) Ag film. The current method can be utilized to characterize the anisotropic elastic-plastic properties of coatings and to provide the constitutive properties for coating performance evaluations.
Monte Carlo calculations of the physical properties of RDX, {beta}-HMX, and TATB
Energy Technology Data Exchange (ETDEWEB)
Sewell, T.D.
1997-09-01
Atomistic Monte Carlo simulations in the NpT ensemble are used to calculate the physical properties of crystalline RDX, {beta}-HMX, and TATB. Among the issues being considered are the effects of various treatments of the intermolecular potential, inclusion of intramolecular flexibility, and simulation size dependence of the results. Calculations of the density, lattice energy, and lattice parameters are made over a wide range of pressures; thereby allowing for predictions of the bulk and linear coefficients of isothermal expansion of the crystals. Comparison with experiment is made where possible.
Energy Technology Data Exchange (ETDEWEB)
Landry, Brian R.; Falk, Martin J.; Subotnik, Joseph E. [Department of Chemistry, University of Pennsylvania, 231 S. 34th Street, Philadelphia, Pennsylvania 19104 (United States)
2013-12-07
In a recent paper, we presented a road map for how Tully's fewest switches surface hopping (FSSH) algorithm can be derived, under certain circumstances, from the mixed quantum-classical Liouville equation. In this communication, we now demonstrate how this new interpretation of surface hopping can yield significantly enhanced results for electronic properties in nonadiabatic calculations. Specifically, we calculate diabatic populations for the spin-boson problem using FSSH trajectories. We show that, for some Hamiltonians, without changing the FSSH algorithm at all but rather simply reinterpreting the ensemble of surface hopping trajectories, we recover excellent results and remove any and all ambiguity about the initial condition problem.
Ab initio calculation of mechanical and thermal properties of U{sub 2}Mo intermetallic
Energy Technology Data Exchange (ETDEWEB)
Jaroszewicz, S., E-mail: jaroszew@tandar.cnea.gov.ar [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina); Losada, E.L.; Garcés, J.E. [DAEE, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (Argentina); Mosca, H.O. [Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica (Argentina)
2013-10-15
We present a study of structural, elastic and thermodynamic properties of tetragonal (C11{sub b}) U{sub 2}Mo by means of density-functional theory based calculations using full-potential linearized augmented plane wave method. In this approach the generalized gradient approximation were used for the exchange–correlation potential calculation. The optimized lattice parameters are in excellent agreement with the experimental data. Through the Debye–Grüneisen model the temperature and pressure dependence of equation of state, bulk modulus, thermal expansion and specific heat have been obtained and discussed in the range of pressure 0–20 GPa and the temperature 0–800 K.
Calculation of Hugoniot properties for shocked nitromethane based on the improved Tsien's EOS
Zhao, Bo; Cui, Ji-Ping; Fan, Jing
2010-06-01
We have calculated the Hugoniot properties of shocked nitromethane based on the improved Tsien’s equation of state (EOS) that optimized by “exact” numerical molecular dynamic data at high temperatures and pressures. Comparison of the calculated results of the improved Tsien’s EOS with the existed experimental data and the direct simulations show that the behavior of the improved Tsien’s EOS is very good in many aspects. Because of its simple analytical form, the improved Tsien’s EOS can be prospectively used to study the condensed explosive detonation coupling with chemical reaction.
Energy Technology Data Exchange (ETDEWEB)
Narayan, A.P. [Univ. of Colorado, Boulder, CO (United States); Rainwater, J.C. [National Institute of Standards and Technology, Boulder, CO (United States); Hanley, H.J.M. [Univ. of Colorado, Boulder, CO (United States)]|[National Institute of Standards and Technology, Boulder, CO (United States)
1995-03-01
A study of the Weissenberg effect (rod climbing in a stirred system) based on nonequilibrium molecular dynamics (NEMD) is reported. Simulation results from a soft-sphere fluid are used to obtain a self-consistent free-surface profile of the fluid of finite compressibility undergoing Couette flow between concentric cylinders. A numerical procedure is then applied to calculate the height profile for a hypothetical fluid with thermophysical properties of the soft-sphere liquid and of a dense colloidal suspension. The height profile calculated is identified with shear thickening and the forms of the viscometric functions. The maximum climb occurs between the cylinders rather than at the inner cylinder.
BERNABE, Anne; Musy, Marjorie; ANDRIEU, Hervé; Calmet, Isabelle
2015-01-01
Urban shape determines the absorption and emission of radiation. Urban fabrics are characterized by the solar trapping effect due to multiple reflections of radiation within the geometry, in turn generating increased energy absorption that contributes to the urban heat island. Interactions between urban radiative properties and urban shape are studied through an analytical development. A simplified solar balance model is developed based on morphological indicators. A processing chain is perfo...
First Principles Calculations for X-ray Resonant Spectra and Elastic Properties
Energy Technology Data Exchange (ETDEWEB)
Lee, Yongbin [Iowa State Univ., Ames, IA (United States)
2004-01-01
In this thesis, we discuss applications of first principles methods to x-ray resonant spectra and elastic properties calculation. We start with brief reviews about theoretical background of first principles methods, such as density functional theory, local density approximation (LDA), LDA+U, and the linear augmented plane wave (LAPW) method to solve Kohn-Sham equations. After that we discuss x-ray resonant scattering (XRMS), x-ray magnetic circular dichroism (XMCD) and the branching problem in the heavy rare earths Ledges. In the last chapter we discuss the elastic properties of the second hardest material AlMgB_{14}.
Srivastava, Vipul; Aynyas, M.; Rajagopalan, M.; Sanyal, S. P.
2008-04-01
Electronic properties of non-magnetic cubic B2-type AIRE (RE = La, Ce and Pr) compounds have been derived from self-consistent tight binding linear muffin tin orbital method at ambient pressure. These compounds show metallic behaviour under ambient conditions. While thermal properties like Debye temperature and Grüneisen constant are calculated at T = 0 K within the Debye-Grüneisen model and compared with the others theoretical results. We have also performed a pressure induced variation of Debye temperature. We have found a decrease in Debye temperature around 40 kbar in all the AIRE compounds.
Numerical calculation of mean intensity and radiative flux in plane-parallel stellar atmospheres
Nariai, K.; Yoshioka, K.
The four-point Gaussian-quadrature formulas of Kegel (1962) for the evaluation of the intensity and flux (F) integrals is improved by using Bessel's interpolation technique and by subdividing the integral range. Steps in the analysis include the calculation of the Gaussian points of division and weightings for the interval (y, z), for a small (y, z), and for (O, z); determination of the precision of n-point formulas in calculating intensity and F; and the derivation of a four-point version of the two-point quadrature method of Cayrel (1960) and Norton (Mihalas, 1967). The numerical results are presented and compared with those of other models. The gray-model delta-F/F ratio calculated by this method is found to be less than 0.01 percent.
Khlystov, A.
1998-01-01
This thesis discusses properties of ambient aerosols in the Netherlands which are controlling the magnitude of the local aerosol radiative forcing. Anthropogenic aerosols influence climate by changing the radiative transfer through the atmosphere via two effects, one is direct and a second
Rozwadowska, Anna; Stachlewska, Iwona S.; Makuch, P.; Markowicz, K. M.; Petelski, T.; Strzałkowska, A.; Zieliński, T.
2013-05-01
Properties of atmospheric aerosols and solar radiation reaching the Earth's surface were measured during Summer 2011 in Sopot, Poland. Three cloudless days, characterized by different directions of incoming air-flows, which are typical transport pathways to Sopot, were used to estimate a radiative forcing due to aerosols present in each air mass.
Khlystov, A.
1998-01-01
This thesis discusses properties of ambient aerosols in the Netherlands which are controlling the magnitude of the local aerosol radiative forcing. Anthropogenic aerosols influence climate by changing the radiative transfer through the atmosphere via two effects, one is direct and a second is indire
Calculation parameters of fields rectangular parallelepiped radiator on an axis of symmetry
Kurdyaev, Y B
2000-01-01
The integral equations for the calculation of the power of kerma from the absorption parallelepiped emitters with the point for detection on the symmetry axis or sequel of edge of the emitter behind the plane protection in absorption medium at any relations of linear dimensions of the emitter were obtained. The relations of sides of the examined emitter were analyzed when replacement it by the point emitter. Calculated results of the changes under removal of detector from the surface of the emitter are given
Kramer, S. L.; Ghosh, V. J.; Breitfeller, M.; Wahl, W.
2016-11-01
Third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produces significantly higher neutron component dose to the experimental floor than a lower energy beam injection and ramped operations. Minimizing this dose will require adequate knowledge of where the miss-steered beam can occur and sufficient EM shielding close to the loss point, in order to attenuate the energy of the particles in the EM shower below the neutron production threshold (Designing supplemental shielding near the loss point using the analytic shielding model is shown to be inadequate because of its lack of geometry specification for the EM shower process. To predict the dose rates outside the tunnel requires detailed description of the geometry and materials that the beam losses will encounter inside the tunnel. Modern radiation shielding Monte-Carlo codes, like FLUKA, can handle this geometric description of the radiation transport process in sufficient detail, allowing accurate predictions of the dose rates expected and the ability to show weaknesses in the design before a high radiation incident occurs. The effort required to adequately define the accelerator geometry for these codes has been greatly reduced with the implementation of the graphical interface of FLAIR to FLUKA. This made the effective shielding process for NSLS-II quite accurate and reliable. The principles used to provide supplemental shielding to the NSLS-II accelerators and the lessons learned from this process are presented.
Ab initio calculation of structure and thermodynamic properties of Zintl aluminide SrAl{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Fu, Zhi-Jian [Chongqing Key Laboratory of Micro/Nano Materials Engineering and Technology, Chongqing (China); Chongqing Univ. of Arts and Sciences (China). School of Electrical and Electronic Engineering; China Academy of Engineering Physics (CAEP), Mianyang, Sichuan (China). National Key Lab. of Shock Wave and Detonation Physics; Jia, Li-Jun [Chongqing Univ. of Arts and Sciences Library (China); Xia, Ji-Hong; Tang, Ke; Li, Zhao-Hong [Chongqing Univ. of Arts and Sciences (China). School of Electrical and Electronic Engineering; Sun, Xiao-Wei [Lanzhou Jiaotong Univ. (China). School of Mathematics and Physics; Chen, Qi-Feng [China Academy of Engineering Physics (CAEP), Mianyang, Sichuan (China). National Key Lab. of Shock Wave and Detonation Physics
2015-07-01
The structural and thermodynamic properties of the orthorhombic and cubic structure SrAl{sub 2} at pressure and temperature are investigated by using the ab initio plane-wave pseudopotential density functional theory method within the generalised gradient approximation (GGA). The calculated lattice parameters are in agreement with the available experimental data and other theoretical results. The phase transition predicted takes place at 0.5 GPa from the orthorhombic to the cubic structure at zero temperature. The thermodynamic properties of the zinc-blende structure SrAl{sub 2} are calculated by the quasi-harmonic Debye model. The pressure-volume relationship and the variations in the thermal expansion a are obtained systematically in the pressure and temperature ranges of 0-5 GPa and 0-500 K, respectively.
Diffusion Monte Carlo ab initio calculations to study wetting properties of graphene
Wu, Yanbin; Zheng, Huihuo; Wagner, Lucas; Aluru, N. R.
2013-11-01
For applications of graphene in water, including for example desalination and DNA sequencing, it is critical to understand the wetting properties of graphene. In this work, we investigate the wetting properties using data from highly accurate diffusion quantum Monte Carlo (DMC) calculations, which treat electron correlation explicitly. Our DMC data show a strong graphene-water interaction, indicating graphene surface is more hydrophilic than previously believed. This has been recently confirmed by experiments [Li et al. Nat. Mater. 2013, doi:10.1038/nmat3709]. The unusually strong interaction can be attributed to weak bonding formed between graphene and water. Besides its inadequate description of dispersion interactions as commonly reported in the literature, density function theory (DFT) fails to describe the correct charge transfer, which leads to an underestimate of graphene-water binding energy. Our DMC calculations can provide insight to experimentalists seeking to understand water-graphene interfaces and to theorists improving DFT for weakly bound systems.
Calculations on nonlinear optical properties for large systems the elongation method
Gu, Feng Long; Springborg, Michael; Kirtman, Bernard
2014-01-01
For design purposes one needs to relate the structure of proposed materials to their NLO (nonlinear optical) and other properties, which is a situation where theoretical approaches can be very helpful in providing suggestions for candidate systems that subsequently can be synthesized and studied experimentally. This brief describes the quantum-mechanical treatment of the response to one or more external oscillating electric fields for molecular and macroscopic, crystalline systems. To calculate NLO properties of large systems, a linear scaling generalized elongation method for the efficient and accurate calculation is introduced. The reader should be aware that this treatment is particularly feasible for complicated three-dimensional and/or delocalized systems that are intractable when applied to conventional or other linear scaling methods.
Tight-binding calculation of radiation loss in photonic crystal CROW.
Ma, Jing; Martínez, Luis Javier; Fan, Shanhui; Povinelli, Michelle L
2013-01-28
The tight binding approximation (TBA) is used to relate the intrinsic, radiation loss of a coupled resonator optical waveguide (CROW) to that of a single constituent resonator within a light cone picture. We verify the validity of the TBA via direct, full-field simulation of CROWs based on the L2 photonic crystal cavity. The TBA predicts that the quality factor of the CROW increases with that of the isolated cavity. Moreover, our results provide a method to design CROWs with low intrinsic loss across the entire waveguide band.
Structure and Properties of the Fe/Y2O3 Interface from First Principles Calculations
Energy Technology Data Exchange (ETDEWEB)
Choudhury, Samrat [Los Alamos National Laboratory; Stanek, Christopher R. [Los Alamos National Laboratory; Uberuaga, Blas P. [Los Alamos National Laboratory
2012-07-31
Fundamentals of radiation damage are: (1) Formation of Frenkel pair (interstitial-vacancy pair) defects in the lattice; (2) Concentration of Frenkel pair defects >>> thermal equilibrium thermodynamic concentration; and (3) The radiation damage response of a material is determined by the fate of these excess Frenkel pair defects in the lattice. The objective is to understand the electronic and atomic structure of Fe/Y{sub 2}O{sub 3} interface and segregation behavior of the alloying elements at the interface. The significance of the results of this report are: (1) Provides a science based approach to design new radiation resistant materials. Obtained two controlling parameters - Dislocation density (composition, orientation relationship) and Oxygen partial pressure; (2) Applicable to any other metal/oxide interfaces (both functional and structural properties at the interface) - (a) Nano Catalysts: Oxide-supported metal catalysts Ni/ZrO{sub 2}, (b) Thermal barrier coatings (Ni/Al{sub 2}O{sub 3}), (c) Corrosion of metals and alloys.
Review of Calculations on Point Defect Properties in Delta-Pu
Energy Technology Data Exchange (ETDEWEB)
Allen, P. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wolfer, W. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-09-08
The results of theoretical predictions of properties for vacancies and self-interstitial atoms (SIA) in δ-Pu are presented and reviewed. Three methods have been used for these predictions, namely the modified embedded atom method (MEAM), density functional theory (DFT) with and without spin polarization, and continuum mechanics (CM) models adapted to plutonium. The properties considered are formation and migration energies, and relaxation volumes of vacancies and SIA. Predicted values vary considerably. Nevertheless, all three methods predict that the activation energy for self-diffusion by vacancies is of similar magnitude as the SIA formation energy. Furthermore, the absolute magnitudes of relaxation volumes for vacancies and SIA are also similar, indicating that there exist no large bias for radiation-induced void swelling.
ding,Yi; Wang, Yanli
2015-01-01
Using first-principles calculations, we investigate the geometric structures and electronic properties of porous silicene and germanene nanosheets, which are the Si and Ge analogues of α−graphyne (referred to as silicyne and germanyne). It is found that the elemental silicyne and germanyne sheets are energetically unfavourable. However, after the C-substitution, the hybrid graphyne-like sheets (c-silicyne/c-germanyne) possess robust energetic and dynamical stabilities. Different from silicene...
Bannikov, V. V.; Shein, I. R.; Ivanovskii, A. L.
2010-05-01
First-principles FLAPW-GGA calculations for six possible polymorphs of ruthenium mononitride RuN indicate that the most stable structure is that of zinc blende rather than the rock salt structure recently reported for synthesized RuN samples. The elastic, electronic properties and the features of chemical bonds of zinc-blende RuN polymorph were investigated and discussed in detail.
Electrical Properties of Hydrous Forsterite Derived from First-Principles Calculations
Institute of Scientific and Technical Information of China (English)
WANG Duo-Jun; LIU Zai-Yang; YI Li; SHI Bao-Ping
2011-01-01
@@ We investigate electrical properties of anhydrous and hydrous forsterite crystalwith 3.2 wt% water by using firstprinciples calculations.The calculation results indicate that the pressure weakly affects the electrical properties of anhydrous forsterite.Two types of defect configurations involving the two hydrogen atoms in different positions are considered.Type 1 involves the entrapment of two hydrogen atoms in a Mg vacancy,which demonstrates little effect on the electronic density of states(DoS) of the forsterite crystal.Type 2 corresponds to the replacement of one hydrogen atom into the Mg vacancy with the other one located in different orientations(free proton model).It is this configuration that can significantly change the DoS of the forsterite crystal.The gap energy of the free proton model derived at different orientations is in the range of 0.693-1.007eV.%We investigate electrical properties of anhydrous and hydrous forsterite crystal with 3.2 wt％ water by using firstprinciples calculations. The calculation results indicate that the pressure weakly affects the electrical properties of anhydrous forsterite. Two types of defect configurations involving the two hydrogen atoms in different positions are considered. Type 1 involves the entrapment of two hydrogen atoms in a Mg vacancy, which demonstrates little effect on the electronic density of states (DoS) of the forsterite crystal. Type 2 corresponds to the replacement of one hydrogen atom into the Mg vacancy with the other one located in different orientations (free proton model).It is this configuration that can significantly change the DoS of the forsterite crystal. The gap energy of the free proton model derived at different orientations is in the range of 0.693-1.007eV.
High-pressure physical properties of magnesium silicate post-perovskite from ab initio calculations
Indian Academy of Sciences (India)
Zi-Jiang Liu; Xiao-Wei Sun; Cai-Rong Zhang; Jian-Bu Hu; Ling-Cang Cai; Qi-Feng Chen
2012-08-01
The structure, thermodynamic and elastic properties of magnesium silicate (MgSiO3) post-perovskite at high pressure are investigated with quasi-harmonic Debye model and ab initio method based on the density functional theory (DFT). The calculated structural parameters of MgSiO3 post-perovskite are consistent with the available experimental results and the recent theoretical results. The Debye temperature, heat capacity and thermal expansion coefficient at high pressures and temperatures are predicted using the quasi-harmonic Debye model. The elastic constants are calculated using stress–strain relations. A complete elastic tensor of MgSiO3 post-perovskite is determined in the wide pressure range. The calculated elastic anisotropic factors and directional bulk modulus show that MgSiO3 post-perovskite possesses high elastic anisotropy.
Calculation of the transport and relaxation properties of dilute water vapor
Hellmann, Robert; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa
2009-07-01
Transport properties of dilute water vapor have been calculated in the rigid-rotor approximation using four different potential energy hypersurfaces and the classical-trajectory method. Results are reported for shear viscosity, self-diffusion, thermal conductivity, and volume viscosity in the dilute-gas limit for the temperature range of 250-2500 K. Of these four surfaces the CC-pol surface of Bukowski et al. [J. Chem. Phys. 128, 094314 (2008)] is in best accord with the available measurements. Very good agreement is found with the most accurate results for viscosity in the whole temperature range of the experiments. For thermal conductivity the deviations of the calculated values from the experimental data increase systematically with increasing temperature to around 5% at 1100 K. For both self-diffusion and volume viscosity, the much more limited number of available measurements are generally consistent with the calculated values, apart from the lower temperature isotopically labeled diffusion measurements.
Institute of Scientific and Technical Information of China (English)
Zi-iiang Liu; Xiao-wei Sun; Cai-rong Zhang; Jian-bo Hu; Ting Song; Jian-hong Qi
2011-01-01
The thermodynamic and elastic properties of magnesium silicate (MgSiO3) perovskite at high pressure are investigated with the quasi-harmonic Debye model and the first-principles method based on the density functional theory.The obtained equation of state is consistent with the available experimental data.The heat capacity and the thermal expansion coefficient agree with the observed values and other calculations at high pressures and temperatures.The elastic constants are calculated using the finite strain method.A complete elastic tensor of MgSiO3 perovskite is determined in the wide pressure range.The geologically important quantities: Young's modulus,Poisson's ratio,Debye temperature,and crystal anisotropy,are derived from the calculated data.
Activation calculation and radiation analysis for China Fusion Engineering Test Reactor
Energy Technology Data Exchange (ETDEWEB)
Chen, Zhi, E-mail: zchen@ustc.edu.cn; Qiao, Shiji; Jiang, Shuai; Xu, X. George
2016-11-01
Highlights: • Activation calculation was performed using FLUKA for the main components of CFETR. • Radionuclides and radioactive wastes were assessed for CFETR. • The Waste Disposal Ratings (WDR) were assessed for CFETR. - Abstract: The activation calculation and analysis for the China Fusion Engineering Test Reactor (CFETR) will play an important role in its system design, maintenance, inspection and assessment of nuclear waste. Using the multi-particle transport code FLUKA and its associated data library, we calculated the radioactivity, specific activity, waste disposal rating from activation products, nuclides in the tritium breeding blanket, shielding layer, vacuum vessel and toroidal field coil (TFC) of CFETR. This paper presents the calculation results including neutron flux, activation products and waste disposal rating after one-year full operation of the CFETR. The findings show that, under the assumption of one-year operation at the 200 MW fusion power, the total radioactivity inventory will be 1.05 × 10{sup 19} Bq at shutdown and 1.03 × 10{sup 17} Bq after ten years. The primary residual nuclide is found to be {sup 55}Fe in ten years after the shutdown. The waste disposal rating (WDR) values are very low (<<1), according to Class C limits, CFETR materials are qualified for shallow land burial. It is shown that CFETR has no serious activation safety issue.
Kienast-Sjögren, Erika; Rolf, Christian; Seifert, Patric; Krieger, Ulrich K.; Luo, Bei P.; Krämer, Martina; Peter, Thomas
2016-06-01
Cirrus, i.e., high, thin clouds that are fully glaciated, play an important role in the Earth's radiation budget as they interact with both long- and shortwave radiation and affect the water vapor budget of the upper troposphere and stratosphere. Here, we present a climatology of midlatitude cirrus clouds measured with the same type of ground-based lidar at three midlatitude research stations: at the Swiss high alpine Jungfraujoch station (3580 m a.s.l.), in Zürich (Switzerland, 510 m a.s.l.), and in Jülich (Germany, 100 m a.s.l.). The analysis is based on 13 000 h of measurements from 2010 to 2014. To automatically evaluate this extensive data set, we have developed the Fast LIdar Cirrus Algorithm (FLICA), which combines a pixel-based cloud-detection scheme with the classic lidar evaluation techniques. We find mean cirrus optical depths of 0.12 on Jungfraujoch and of 0.14 and 0.17 in Zürich and Jülich, respectively. Above Jungfraujoch, subvisible cirrus clouds (τ change in cloud morphology at Jungfraujoch above ˜ 13 km, possibly because high particle number densities form in the observed cirrus clouds, when many ice crystals nucleate in the high supersaturations following rapid uplifts in lee waves above mountainous terrain. The retrieved optical properties are used as input for a radiative transfer model to estimate the net cloud radiative forcing, CRFNET, for the analyzed cirrus clouds. All cirrus detected here have a positive CRFNET. This confirms that these thin, high cirrus have a warming effect on the Earth's climate, whereas cooling clouds typically have cloud edges too low in altitude to satisfy the FLICA criterion of temperatures below -38 °C. We find CRFNET = 0.9 W m-2 for Jungfraujoch and 1.0 W m-2 (1.7 W m-2) for Zürich (Jülich). Further, we calculate that subvisible cirrus (τ < 0.03) contribute about 5 %, thin cirrus (0.03 < τ < 0.3) about 45 %, and opaque cirrus (0.3 < τ) about 50 % of the total cirrus radiative forcing.
Merk, C.; Cermak, J.; Bendix, J.
2009-04-01
Fog and low stratus (FLS) impact on traffic safety and air quality; knowledge of the FLS distribution in time and space therefore is of great value. A new algorithm is developed to detect fog and low stratus with MSG/SEVIRI data at night. An essential component of this study needed for the discrimination between elevated and ground fog is the derivation of microphysical properties of low clouds. A radiative transfer model is used to model optical and microphysical properties (optical thickness, effective droplet radius and liquid water path) to create a lookup table for the operational algorithm. To find a suitable radiative transfer model for this study, two models are compared: Streamer and libRadtran. Streamer is a radiative transfer model that can be used for a wide variety of atmospheric and surface conditions. The computing time is relatively short and it is easy to handle, but the MSG/SEVIRI channels are represented only coarsely by the radiative transfer code's bands. Absorption effects may lead to inaccuracies in infrared channels. Streamer has got two radiative transfer solvers. LibRadtran is a library of radiative transfer routines and programs. The central program can be used as a tool for the simulation of instrument signals. It has got eight radiative transfer solvers. There are four different methods given for the spectral calculations, depending on the time and the purpose of the calculation is used for. For both radiative transfer models, all infrared channels except the water vapour channels are used and the optical thickness, effective droplet radius, surface temperature and the satellite zenith angle are varied. The aim of this study is to find out which radiative transfer model is most useful for the retrieval of FLS microphysics. Output from both radiative transfer models is presented and compared. The implementation in FLS property retrieval is shown and discussed.
Effects of alloying elements on elastic properties of Al by first-principles calculations
Directory of Open Access Journals (Sweden)
Wang J.
2014-01-01
Full Text Available The effects of alloying elements (Co, Cu, Fe, Ge, Hf, Mg, Mn, Ni, Si, Sr, Ti, V, Y, Zn, and Zr on elastic properties of Al have been investigated using first-principles calculations within the generalized gradient approximation. A supercell consisting of 31 Al atoms and one solute atom is used. A good agreement is obtained between calculated and available experimental data. Lattice parameters of the studied Al alloys are found to be depended on atomic radii of solute atoms. The elastic properties of polycrystalline aggregates including bulk modulus (B, shear modulus (G, Young’s modulus (E, and the B/G ratio are also determined based on the calculated elastic constants (cij’s. It is found that the bulk modulus of Al alloys decreases with increasing volume due to the addition of alloying elements and the bulk modulus is also related to the total molar volume (Vm and electron density (nAl31x with the relationship of nAl31x=1.0594+0.0207√B/Vm. These results are of relevance to tailor the properties of Al alloys.
Simplifying the calculation of light scattering properties for black carbon fractal aggregates
Directory of Open Access Journals (Sweden)
A. J. A. Smith
2014-02-01
Full Text Available Black carbon fractal aggregates have complicated shapes that make the calculation of their optical properties particularly computationally expensive. Here, a method is presented to estimate fractal aggregate light scattering properties by optimising simplified models to full light scattering calculations. It is found that there are no possible spherical models (at any size or refractive index that well represent the light scattering in the visible, or near-thermal infrared. As such, parameterisations of the light scattering as a function of the number of aggregate particles is presented as the most pragmatic choice for modelling distributions of black carbon when the large computational overheads of rigorous scattering calculations cannot be justified. This parameterisation can be analytically integrated to provide light scattering properties for log-normal distributions of black carbon fractal aggregates and return extinction cross-sections with 0.1% accuracy for typical black carbon size distributions. Scattering cross-sections and the asymmetry parameter can be obtained to within 3%.
Ab initio calculations of the optical properties of crystalline and liquid InSb
Energy Technology Data Exchange (ETDEWEB)
Sano, Haruyuki, E-mail: h-sano@ishikawa-nct.ac.jp [National Institute of Technology, Ishikawa College, Kitacyujo, Tsubata, Ishikawa 929-0392 (Japan); Mizutani, Goro [School of Materials Science, Japan Advanced Institute of Science and Technology, Tatsunokuchi, Ishikawa 923-1292 (Japan)
2015-11-15
Ab initio calculations of the electronic and optical properties of InSb were performed for both the crystalline and liquid states. Two sets of atomic structure models for liquid InSb at 900 K were obtained by ab initio molecular dynamics simulations. To reduce the effect of structural peculiarities in the liquid models, an averaging of the two sets of the calculated electronic and optical properties corresponding to the two liquid models was performed. The calculated results indicate that, owing to the phase transition from crystal to liquid, the density of states around the Fermi level increases. As a result, the energy band gap opening near the Fermi level disappears. Consequently, the optical properties change from semiconductor to metallic behavior. Namely, owing to the melting of InSb, the interband transition peaks disappear and a Drude-like dispersion is observed in the optical dielectric functions. The optical absorption at a photon energy of 3.06 eV, which is used in Blu-ray Disc systems, increases owing to the melting of InSb. This increase in optical absorption is proposed to result from the increased optical transitions below 2 eV.
A new, coupled transport-diffusion method for radiative transfer calculations
Energy Technology Data Exchange (ETDEWEB)
Wollaber, A. B.; Warsa, J. S. [Los Alamos National Laboratory, MS D409, P.O. Box 1663, Los Alamos NM, 87545 (United States)
2013-07-01
We derive and present a new frequency- and angle-integrated low-order system of equations designed to enhance the accuracy of a coupled, high-order (transport) solution of the thermal radiative transfer equations. In particular, our new low-order system is designed to use intensity-weighted opacities and anisotropic diffusion coefficients generated by a solution of the Implicit Monte Carlo (IMC) equations in order to predict the spatial dependence of the material temperature and radiation energies in the ensuing time cycle. The predicted temperature solution can then be exploited to generate appropriately time-centered opacities, specific heats, and Planck emission spectra for the upcoming IMC solution. Additionally, the relatively inexpensive solution of the low-order system can be iteratively solved to recommend an adaptive time step size before the IMC solution is computed. A test implementation has been implemented using existing software available from the Jayenne and Capsaicin projects at Los Alamos National Laboratory. We present initial results from a new driver code that has integrated these stochastic and deterministic software packages. (authors)
Radiation Transport Calculation of the UGXR Collimators for the Jules Horowitz Reactor (JHR)
Chento, Yelko; Hueso, César; Zamora, Imanol; Fabbri, Marco; Fuente, Cristina De La; Larringan, Asier
2017-09-01
Jules Horowitz Reactor (JHR), a major infrastructure of European interest in the fission domain, will be built and operated in the framework of an international cooperation, including the development and qualification of materials and nuclear fuel used in nuclear industry. For this purpose UGXR Collimators, two multi slit gamma and X-ray collimation mechatronic systems, will be installed at the JHR pool and at the Irradiated Components Storage pool. Expected amounts of radiation produced by the spent fuel and X-ray accelerator implies diverse aspects need to be verified to ensure adequate radiological zoning and personnel radiation protection. A computational methodology was devised to validate the Collimators design by means of coupling different engineering codes. In summary, several assessments were performed by means of MCNP5v1.60 to fulfil all the radiological requirements in Nominal scenario (TEDE < 25µSv/h) and in Maintenance scenario (TEDE < 2mSv/h) among others, detailing the methodology, hypotheses and assumptions employed.
Calculation of wideband ultrasonic fields radiated by immersed transducers into solids
Energy Technology Data Exchange (ETDEWEB)
Lhemery, A.; Calmon, P.; Mephane, M.
1996-12-31
In ultrasonic nondestructive testing (NDT), configurations of immersion techniques where transducers radiate through non-planar interfaces are often encountered, e.g., pipe inspection where the probe can be scanned either inside or outside the pipe. When local radii of curvature are far larger that typical wave paths in the coupling fluid and into the piece, field predictions can often be made assuming a plane interface. For smaller radii, such an approximation is not valid. The model developed at the French Atomic ENergy Commission (CEA) to predict ultrasonic fields radiated by wideband transducers through liquid-interfaces (called Champ-Sons) is based on a modification of the Rayleigh integral to take account of refraction. It is derived under the geometrical optics approximation (GO) which introduces two factors: the transmission coefficient between the two media of elementary contributions from source-points to field-points and the so-called `divergence factor` of the transmitted rays (denoted by DF), accounting for the principal radii of curvature of the retransmitted rays (denoted by DF), accounting for the principal radii of curvature of the refracted wave fronts (initially spherical in the coupling medium). (authors).
Radionuclide Ionization in Protoplanetary Disks: Calculations of Decay Product Radiative Transfer
Cleeves, L Ilsedore; Bergin, Edwin A; Visser, Ruud
2013-01-01
We present simple analytic solutions for the ionization rate $\\zeta_{\\rm{SLR}}$ arising from the decay of short-lived radionuclides (SLRs) within protoplanetary disks. We solve the radiative transfer problem for the decay products within the disk, and thereby allow for the loss of radiation at low disk surface densities; energy loss becomes important outside $R\\gtrsim30$ for typical disk masses $M_g=0.04$ M$_\\odot$. Previous studies of chemistry/physics in these disks have neglected the impact of ionization by SLRs, and often consider only cosmic rays (CRs), because of the high CR-rate present in the ISM. However, recent work suggests that the flux of CRs present in the circumstellar environment could be substantially reduced by relatively modest stellar winds, resulting in severely modulated CR ionization rates, $\\zeta_{\\rm{CR}}$, equal to or substantially below that of SLRs ($\\zeta_{\\rm{SLR}}\\lesssim10^{-18}$ s$^{-1}$). We compute the net ionizing particle fluxes and corresponding ionization rates as a func...
Radiation Transport Calculation of the UGXR Collimators for the Jules Horowitz Reactor (JHR
Directory of Open Access Journals (Sweden)
Chento Yelko
2017-01-01
Full Text Available Jules Horowitz Reactor (JHR, a major infrastructure of European interest in the fission domain, will be built and operated in the framework of an international cooperation, including the development and qualification of materials and nuclear fuel used in nuclear industry. For this purpose UGXR Collimators, two multi slit gamma and X-ray collimation mechatronic systems, will be installed at the JHR pool and at the Irradiated Components Storage pool. Expected amounts of radiation produced by the spent fuel and X-ray accelerator implies diverse aspects need to be verified to ensure adequate radiological zoning and personnel radiation protection. A computational methodology was devised to validate the Collimators design by means of coupling different engineering codes. In summary, several assessments were performed by means of MCNP5v1.60 to fulfil all the radiological requirements in Nominal scenario (TEDE < 25µSv/h and in Maintenance scenario (TEDE < 2mSv/h among others, detailing the methodology, hypotheses and assumptions employed.
Mechanical properties of W–Ti alloys from first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Jiang, D.Y. [Department of Materials Science and Engineering, Nanchang University, Nanchang 330047 (China); Department of Physics, Nanchang University, Nanchang 330047 (China); School of Basic Sciences, Jiangxi University of Technology, Nanchang 330098 (China); Ouyang, C.Y. [Department of Physics, Jiangxi Normal University, Nanchang 330022 (China); Liu, S.Q., E-mail: sqlgroup@ncu.edu.cn [Department of Materials Science and Engineering, Nanchang University, Nanchang 330047 (China); Department of Physics, Nanchang University, Nanchang 330047 (China)
2016-05-15
Highlights: • The mechanical properties of the W{sub 1-x}Ti{sub x} alloys are calculated from DFT. • Ti alloying enhances the ductility of W metal substantially. • The mechanical strength of W-Ti alloys is slightly weaker than W while stronger than Ti. - Abstract: The effect of Ti concentration on the fundamental mechanical properties of W-Ti alloys has been studied from first principles calculations. The lattice constants, the cell volumes and the formation energies of the W{sub 1-x}Ti{sub x} (x = 0.0625, 0.125, 0.1875, 0.25, 0.5) alloys were calculated. It is shown that Ti alloying in bcc W lattice is thermodynamically favorable when the Ti concentration is lower than 25% and the W{sub 0.8125}Ti{sub 0.1875} have the lowest formation energy. With the optimized geometry and lattice, the elastic constants are calculated and then the elastic moduli and other mechanical parameters are derived. Results show that although the mechanical strength of the W-Ti alloys is lower than that of pure W metal, it is much higher than that of pure Ti metal. On the other hand, the B/G ratio and the Poisson's ratio of the W-Ti alloys is much higher than that of pure W, and even higher than that of pure Ti, indicating that Ti alloying can improve the ductility of bcc W substantially.
Bock, Steffen; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa
2004-05-01
The transport properties of pure carbon dioxide have been calculated from the intermolecular potential using the classical trajectory method. Results are reported in the dilute-gas limit for thermal conductivity and thermomagnetic coefficients for temperatures ranging from 200 K to 1000 K. Three recent carbon dioxide potential energy hypersurfaces have been investigated. Since thermal conductivity is influenced by vibrational degrees of freedom, not included in the rigid-rotor classical trajectory calculation, a correction for vibration has also been employed. The calculations indicate that the second-order thermal conductivity corrections due to the angular momentum polarization (Bukowski et al. (1999) are in good agreement with the available experimental data. They underestimate the best experimental data at room temperature by 1% and in the range up to 470 K by 1%-3%, depending on the data source. Outside this range the calculated values, we believe, may be more reliable than the currently available experimental data. Our results are consistent with measurements of the thermomagnetic effect at 300 K only when the vibrational degrees of freedom are considered fully. This excellent agreement for these properties indicates that particularly the potential surface of Bukowski et al. provides a realistic description of the anisotropy of the surface.
Materials by design: methodological developments in the calculation of excited-state properties
Govoni, Marco
Density functional theory (DFT) is one of the main tools used in first principle simulations of materials; however several of the current approximations of exchange and correlation functionals do not provide the level of accuracy required for predictive calculations of excited state properties. The application to heterogeneous systems of more accurate post-DFT approaches such as Many-Body Perturbation Theory (MBPT) - for example to nanostructured, disordered, and defective materials - has been hindered by high computational costs. In this talk recent methodological developments in MBPT calculations will be discussed, as recently implemented in the open source code WEST, which efficiently exploits HPC architectures. Results using a formulation that does not require the explicit calculation of virtual states, nor the storage and inversion of large dielectric matrices will be presented; these results include quasi particle energies for systems with thousands of electrons and encompass the electronic structure of aqueous solutions, spin defects in insulators, and benchmarks for molecules and solids containing heavy elements. Simplifications of MBPT calculations based on the use of static response properties, such as dielectric-dependent hybrid functionals, will also be discussed. Work done in collaboration with Hosung Seo, Peter Scherpelz, Ikutaro Hamada, Jonathan Skone, Alex Gaiduk, T. Anh Pham, and Giulia Galli. Supported by DOE-BES.
LDA +U calculation of electronic and thermoelectric properties of doped CuCoO 2
Knížek, K.
2015-02-01
Doped CuCoO2 is a candidate oxide material for thermoelectric power generation. The evolution of the band structure and thermoelectric properties of CuCoO2 upon hole and electron doping in the CoO2 layer and hole doping at the Cu site were calculated by the local-density approximation (LDA) and LDA +U methods and using standard Boltzmann theory. The doping was simulated by the virtual atom approximation and the supercell approach and the results were compared with previous calculations using the rigid band approximation. The calculated thermopowers are comparable for the virtual atom and rigid band approximations, but the thermopower obtained from the supercell calculation is significantly lower. The reason is the similar energy of Co and Cu d orbitals and the hybridization of symmetrically related Co a1 g and Cu dz2 orbitals. As a consequence, both cations contribute to the bands around the Fermi level and hence a substitution at any of the cation sites alters the band structure at EF and affects the thermoelectric properties. Our results show that in the case of hole doping, higher thermopower is obtained for substitution at the Cu site than in the CoO2 layer.
Energy Technology Data Exchange (ETDEWEB)
Duan, Yuhua
2012-11-02
Since current technologies for capturing CO{sub 2} to fight global climate change are still too energy intensive, there is a critical need for development of new materials that can capture CO{sub 2} reversibly with acceptable energy costs. Accordingly, solid sorbents have been proposed to be used for CO{sub 2} capture applications through a reversible chemical transformation. By combining thermodynamic database mining with first principles density functional theory and phonon lattice dynamics calculations, a theoretical screening methodology to identify the most promising CO{sub 2} sorbent candidates from the vast array of possible solid materials has been proposed and validated. The calculated thermodynamic properties of different classes of solid materials versus temperature and pressure changes were further used to evaluate the equilibrium properties for the CO{sub 2} adsorption/desorption cycles. According to the requirements imposed by the pre- and post- combustion technologies and based on our calculated thermodynamic properties for the CO{sub 2} capture reactions by the solids of interest, we were able to screen only those solid materials for which lower capture energy costs are expected at the desired pressure and temperature conditions. Only those selected CO{sub 2} sorbent candidates were further considered for experimental validations. The ab initio thermodynamic technique has the advantage of identifying thermodynamic properties of CO{sub 2} capture reactions without any experimental input beyond crystallographic structural information of the solid phases involved. Such methodology not only can be used to search for good candidates from existing database of solid materials, but also can provide some guidelines for synthesis new materials. In this presentation, we first introduce our screening methodology and the results on a testing set of solids with known thermodynamic properties to validate our methodology. Then, by applying our computational method
Liu, H.; Crawford, J. H.; Pierce, R. B.; Considine, D. B.; Logan, J. A.; Duncan, B. N.; Norris, P.; Platnick, S. E.; Chen, G.; Yantosca, R. M.; Evans, M. J.
2005-12-01
Representation of clouds in global models poses a significant challenge since most cloud processes occur on sub-grid scales and must be parameterized. Uncertainties in cloud distributions and optical properties are therefore a limiting factor in model assessments of the radiative effect of clouds on global tropospheric chemistry. We present an analysis of the sensitivity of the radiative effect of clouds to cloud vertical distributions and optical properties with the use of the GEOS-CHEM global 3-D chemistry transport model coupled with the Fast-J radiative transfer algorithm. GEOS-CHEM was driven with a series of meteorological archives (GEOS1-STRAT, GEOS-3, and GEOS-4) generated by the Goddard Earth Observing System data assimilation system (GEOS DAS) at the NASA global Modeling and Assimilation Office (GMAO), which have significantly different cloud optical depths and vertical distributions. The column cloud optical depths in GEOS-3 generally agree with the satellite retrieval products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the International Satellite Cloud Climatology Project (ISCCP) within ±10%, while those in GEOS1-STRAT and GEOS-4 are too low by factors of about 5 and 2, respectively. With respect to vertical distribution, clouds in GEOS-4 are optically much thinner in the tropical upper troposphere compared to those in GEOS1-STRAT and GEOS-3. Assuming linear scaling of cloud optical depth with cloud fraction in a grid-box, our model calculations indicate that the changes in global mean hydroxyl radical (OH) due to the radiative effect of clouds in June are about -1% (GEOS1-STRAT), 1% (GEOS-3), and 14% (GEOS-4), respectively. The effects on global mean OH are similar for GEOS1-STRAT and GEOS-3 due to similar vertical distributions of clouds, even though the column cloud optical depths in the two archives differ by a factor of about 5. Clouds in GEOS-4 have a much larger impact on global mean OH because more solar radiation is
Using TraFiC 4 to calculate and minimize emittance growth due to coherent synchrotron radiation
Kabel, A.; Dohlus, M.; Limberg, T.
2000-11-01
Coherent synchrotron radiation occurs when short bunches travel on strongly bent trajectories. Its effects on high-quality beams can be severe and are well understood qualitatively. For quantitative results, however, one has to rely on numerical methods. The recent interest in high quality, high-current electron beams has generated considerable efforts to understand and minimize the effects of CSR on beam quality. By now several simulation codes, utilizing different approaches and making different approximations, exist. We describe in some detail the coder TraFiC 4 developed at DESY for design and analysis purposes. It calculates the fields acting on the pariticles from first principles and tracks particles through them in the laboratory frame. We present calculational results for three applications and give some comparison with experimental data.
Electronic properties of tantalum pentoxide polymorphs from first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Lee, J. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor 48109 (United States); Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor 48109 (United States); Lu, W. [Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor 48109 (United States); Kioupakis, E., E-mail: kioup@umich.edu [Department of Materials Science and Engineering, University of Michigan, Ann Arbor 48109 (United States)
2014-11-17
Tantalum pentoxide (Ta{sub 2}O{sub 5}) is extensively studied for its attractive properties in dielectric films, anti-reflection coatings, and resistive switching memory. Although various crystalline structures of tantalum pentoxide have been reported, its structural, electronic, and optical properties still remain a subject of research. We investigate the electronic and optical properties of crystalline and amorphous Ta{sub 2}O{sub 5} structures using first-principles calculations based on density functional theory and the GW method. The calculated band gaps of the crystalline structures are too small to explain the experimental measurements, but the amorphous structure exhibits a strong exciton binding energy and an optical band gap (∼4 eV) in agreement with experiment. We determine the atomic orbitals that constitute the conduction band for each polymorph and analyze the dependence of the band gap on the atomic geometry. Our results establish the connection between the underlying structure and the electronic and optical properties of Ta{sub 2}O{sub 5}.
On the radiative properties of soot aggregates - Part 2: Effects of coating
Liu, Fengshan; Yon, Jérôme; Bescond, Alexandre
2016-03-01
The effects of weakly absorbing material coating on soot have attracted considerable research attention in recent years due to the significant influence of such coating on soot radiative properties and the large differences predicted by different numerical models. Soot aggregates were first numerically generated using the diffusion limited cluster aggregation algorithm to produce fractal aggregates formed by log-normally distributed polydisperse spherical primary particles in point-touch. These aggregates were then processed by adding a certain amount of primary particle overlapping and necking to simulate the soot morphology observed from transmission electron microscopy images. After this process, a layer of WAM coating of different thicknesses was added to these more realistic soot aggregates. The radiative properties of these coated soot aggregates over the spectral range of 266-1064 nm were calculated by the discrete dipole approximation (DDA) using the spectrally dependent refractive index of soot for four aggregates containing Np=1, 20, 51 and 96 primary particles. The considered coating thicknesses range from 0% (no coating) up to 100% coating in terms of the primary particle diameter. Coating enhances both the particle absorption and scattering cross sections, with much stronger enhancement to the scattering one, as well as the asymmetry factor and the single scattering albedo. The absorption enhancement is stronger in the UV than in the visible and the near infrared. The simple corrections to the Rayleigh-Debye-Gans fractal aggregates theory for uncoated soot aggregates are found not working for coated soot aggregates. The core-shell model significantly overestimates the absorption enhancement by coating in the visible and the near infrared compared to the DDA results of the coated soot particle. Treating an externally coated soot aggregate as an aggregate formed by individually coated primary particles significantly underestimates the absorption
Thermodynamics and elastic properties of Ta from first-principles calculations
Institute of Scientific and Technical Information of China (English)
Li Qiang; Huang Duo-Hui; Cao Qi-Long; Wang Fan-Hou; Cai Ling-Cang; Zhang Xiu-Lu; Jing Fu-Qian
2012-01-01
Within the framework of the quasiharmonic approximation,the thermodynamics and elastic properties of Ta,including phonon density of states (DOS),equation of state,linear thermal expansion coefficient,entropy,enthalpy,heat capacity,elastic constants,bulk modulus,shear modulus,Young's modulus,microhardness,and sound velocity,are studied using the first-principles projector-augmented wave method.The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon DOS and the Debye model.The thermal electronic contribution to Helmholtz free energy is estimated from the integration over the electronic DOS.By comparing the experimental results with the calculation results from the first-principles and the Debye model,it is found that the thermodynamic properties of Ta are depicted well by the first-principles.The elastic properties of Ta from the first-principles are consistent with the available experimental data.
Directory of Open Access Journals (Sweden)
Dwyer Donard S
2005-08-01
Full Text Available Abstract Background Electronic properties of amino acid side chains such as inductive and field effects have not been characterized in any detail. Quantum mechanics (QM calculations and fundamental equations that account for substituent effects may provide insight into these important properties. PM3 analysis of electron distribution and polarizability was used to derive quantitative scales that describe steric factors, inductive effects, resonance effects, and field effects of amino acid side chains. Results These studies revealed that: (1 different semiempirical QM methods yield similar results for the electronic effects of side chain groups, (2 polarizability, which reflects molecular deformability, represents steric factors in electronic terms, and (3 inductive effects contribute to the propensity of an amino acid for α-helices. Conclusion The data provide initial characterization of the substituent effects of amino acid side chains and suggest that these properties affect electron density along the peptide backbone.
Liang, Zuozhong; Wang, Wei; Zhang, Min; Wu, Fei; Chen, Jian-Feng; Xue, Chunyu; Zhao, Hong
2017-04-01
The structural, mechanical and thermodynamic properties of ZrO2 polymorphs (namely, monoclinic (P21/c), tetragonal (P42/nmc), cubic (Fm 3 bar m), and orthorhombic (Pbca and Pnma)) are investigated systematically by employing DFT functionals (LDA, PBE and PW91). It is found that the structural parameters of ZrO2 polymorphs calculated by PBE and PW91 functionals are highly consistent with previous experiments with low absolute relative error (ARE). Moreover, all considered structures are mechanically stable according to the Born-Huang criterion and the PBE and PW91 functionals are more accurate than the LDA functional in predicting mechanical and thermodynamic properties. Significantly, we described mechanical and thermodynamic properties of ZrO2 polymorphs by introducing the charge density difference of related surfaces, which provides a better understanding of different behaviors of elastic constants (Cij) in various crystal structures of ZrO2.
Effect of Ionizing Radiation on the Properties of Porous Silicon Nanostructures
Directory of Open Access Journals (Sweden)
I.B. Olenych
2015-12-01
Full Text Available The influence of ionizing radiation from 226Ra source on the electrical and photoluminescent properties of porous silicon nanostructures was investigated. After the radiation exposure, AC resistance of experimental samples decreased and luminescence band was changed. Temperature dependencies of electrical conductivity and depolarization current were studied in 80-325 K temperature range. Effect of radiation on the energy distribution of localized electronic states in porous silicon based structures is analyzed. Obtained results expand the application prospective of porous silicon for radiation sensing.
Sanli, Aydin; Beser, Bediha; Edwardson, John R; Magnier, Sylvie; Ahmed, Ergin H; Marjatta Lyyra, A
2015-09-14
We report here ab initio calculated electronic transition dipole moments for the sodium dimer ion pair states of (1)Σg (+) symmetry. They vary strongly as a function of internuclear distance because of the effect of the Na(+) + Na(-) ion pair potential, which also causes the formation of additional wells and shoulders in the molecular potential energy curves. We also present a computational study of the transition dipole moment matrix elements and lifetimes for these ion-pair states.
RADIONUCLIDE IONIZATION IN PROTOPLANETARY DISKS: CALCULATIONS OF DECAY PRODUCT RADIATIVE TRANSFER
Energy Technology Data Exchange (ETDEWEB)
Cleeves, L. Ilsedore; Adams, Fred C.; Bergin, Edwin A.; Visser, Ruud [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
2013-11-01
We present simple analytic solutions for the ionization rate ζ{sub SLR} arising from the decay of short-lived radionuclides (SLRs) within protoplanetary disks. We solve the radiative transfer problem for the decay products within the disk, and thereby allow for the loss of radiation at low disk surface densities; energy loss becomes important outside R ∼> 30 AU for typical disk masses M{sub g} = 0.04 M{sub ☉}. Previous studies of chemistry/physics in these disks have neglected the impact of ionization by SLRs, and often consider only cosmic rays (CRs), because of the high CR-rate present in the interstellar medium. However, recent work suggests that the flux of CRs present in the circumstellar environment could be substantially reduced by relatively modest stellar winds, resulting in severely modulated CR ionization rates, ζ{sub CR}, equal to or substantially below that of SLRs (ζ{sub SLR} ∼< 10{sup –18} s{sup –1}). We compute the net ionizing particle fluxes and corresponding ionization rates as a function of position within the disk for a variety of disk models. The resulting expressions are especially simple for the case of vertically Gaussian disks (frequently assumed in the literature). Finally, we provide a power-law fit to the ionization rate in the midplane as a function of gas disk surface density and time. Depending on location in the disk, the ionization rates by SLRs are typically in the range ζ{sub SLR} ∼ (1-10) × 10{sup –19} s{sup –1}.
Ground-based measurements of aerosol optical properties and radiative forcing in North China
Institute of Scientific and Technical Information of China (English)
Hongbin Chen; Xiangao Xia; Pucai Wang; Wenxing Zhang
2007-01-01
In order to gain an insight into the aerosol properties and their climatic effect over the continental source regions of China, it is of significance to carry out long-term ground-based measurements of aerosol optical properties and radiative forcing. A couple of temporary and permanent Aerosol Robotic Network (AERONET) sites and three comprehensive radiative sites were established in China as a result of international cooperation in recent years. Heavy aerosol loading and significant temporal and spatial variation over North China are revealed by the AERONET data.Aerosol-induced reductions in surface radiation budget are examined on the basis of collocated observations by sun photometers and pyranometers.
The utilize of gamma radiation on the examination of mechanical properties of polymeric materials
Directory of Open Access Journals (Sweden)
F. Greškovič
2012-04-01
Full Text Available The article deals about the application area of radiation crosslinking of plastics, which follows after the injection moulding. The main objective of the presented article is the research of influence irradiation dosage on mechanical properties of materials: PP filled by 15 % of mineral filler – talc. Mechanical properties - tensile strength and impact strength by Charpy were examined in dependence on absorbed dose of the gamma rays on various conditions and were compared with non-irradiated samples. Radiation processing involves mainly the use of either electron beams from electron accelerators or gamma radiation from Cobalt-60 sources.
Band Structure and Optical Properties of Kesterite Type Compounds: first principle calculations
Palaz, S.; Unver, H.; Ugur, G.; Mamedov, A. M.; Ozbay, E.
2017-02-01
In present work, our research is mainly focused on the electronic structures, optical and magnetic properties of Cu2FeSnZ4 (Z = S, Se) compounds by using ab initio calculations within the generalized gradient approximation (GGA). The calculations are performed by using the Vienna ab-initio simulation package (VASP) based on the density functional theory. The band structure of the Cu2FeSnZ4 ( Z = S, Se) compounds for majority spin (spin-up) and minority spin (spin-down) were calculated. It is seen that for these compounds, the majority spin states cross the Fermi level and thus have the metallic character, while the minority spin states open the band gaps around the Fermi level and thus have the narrow-band semiconducting nature. For better understanding of the electronic states, the total and partial density of states were calculated, too. The real and imaginary parts of dielectric functions and hence the optical functions such as energy-loss function, the effective number of valance electrons and the effective optical dielectric constant for Cu2FeSnZ4 (Z = S, Se) compounds were also calculated.
Roondhe, Basant; Upadhyay, Deepak; Som, Narayan; Pillai, Sharad B.; Shinde, Satyam; Jha, Prafulla K.
2017-03-01
The structural, electronic, dynamical and thermodynamical properties of CmX (X = N, P, As, Sb, and Bi) compounds are studied using first principles calculations within density functional theory. The Perdew-Burke-Ernzerhof spin polarized generalized gradient approximation and Perdew-Wang (PW) spin polarized local density approximation as the exchange correlational functionals are used in these calculations. There is a good agreement between the present and previously reported data. The calculated electronic density of states suggests that the curium monopnictides are metallic in nature, which is consistent with earlier studies. The significant values of magnetic moment suggest their magnetic nature. The phonon dispersion curves and phonon density of states are also calculated, which depict the dynamical stability of these compounds. There is a significant separation between the optical and acoustical phonon branches. The temperature dependence of the thermodynamical functions are also calculated and discussed. Internal energy and vibrational contribution to the Helmholtz free energy increases and decreases, respectively, with temperature. The entropy increases with temperature. The specific heat at constant volume and Debye temperature obey Debye theory. The temperature variation of the considered thermodynamical functions is in line with those of other crystalline solids.
Investigation of radiation keeping property of barite coated cloth via image processing method
Energy Technology Data Exchange (ETDEWEB)
Kilincarslan, S.; Akkurt, I.; Molla, T.; Akarslan, F. [Department of Construction Education, Suleyman Demirel University, Isparta (Turkey); Department of Physics, Science Faculty, Suleyman Demirel University, Isparta (Turkey); Department of Construction Education, Suleyman Demirel University, Isparta (Turkey); Textil Engineering, Engineering Faculty, Suleyman Demirel University, Isparta (Turkey)
2012-09-06
Preservative clothes which are able to absorb radiation beam are needed not only for saving people working at radioactive environment but also for saving others from natural and man-made radiation sources we are exposed in daily life. Barite is a mineral which can be used for armour plating because of high atomic numbered element barium constituent of barite. In this study, armour plating property of barite was applied to fabrics. Barite coated fabric having characteristic of keeping radiation was obtained by penetrating barite on cloth via coating method. Radiation keeping property of fabrics obtained was determined via image processing. The results of experiments showed that barite coated fabrics have blocked radiation more than normal fabrics have done.
Xie, Tianwu; Kuster, Niels; Zaidi, Habib
2017-08-01
Computational phantoms are commonly used in internal radiation dosimetry to assess the amount and distribution pattern of energy deposited in various parts of the human body from different internal radiation sources. Radiation dose assessments are commonly performed on predetermined reference computational phantoms while the argument for individualized patient-specific radiation dosimetry exists. This study aims to evaluate the influence of body habitus on internal dosimetry and to quantify the uncertainties in dose estimation correlated with the use of fixed reference models. The 5-year-old IT’IS male phantom was modified to match target anthropometric parameters, including body weight, body height and sitting height/stature ratio (SSR), determined from reference databases, thus enabling the creation of 125 5-year-old habitus-dependent male phantoms with 10th, 25th, 50th, 75th and 90th percentile body morphometries. We evaluated the absorbed fractions and the mean absorbed dose to the target region per unit cumulative activity in the source region (S-values) of F-18 in 46 source regions for the generated 125 anthropomorphic 5-year-old hybrid male phantoms using the Monte Carlo N-Particle eXtended general purpose Monte Carlo transport code and calculated the absorbed dose and effective dose of five 18F-labelled radiotracers for children of various habitus. For most organs, the S-value of F-18 presents stronger statistical correlations with body weight, standing height and sitting height than BMI and SSR. The self-absorbed fraction and self-absorbed S-values of F-18 and the absorbed dose and effective dose of 18F-labelled radiotracers present with the strongest statistical correlations with body weight. For 18F-Amino acids, 18F-Brain receptor substances, 18F-FDG, 18F-L-DOPA and 18F-FBPA, the mean absolute effective dose differences between phantoms of different habitus and fixed reference models are 11.4%, 11.3%, 10.8%, 13.3% and 11.4%, respectively. Total body
Dong, Xiquan; Xi, Baike; Qiu, Shaoyue; Minnis, Patrick; Sun-Mack, Sunny; Rose, Fred
2016-09-01
Retrievals of cloud microphysical properties based on passive satellite imagery are especially difficult over snow-covered surfaces because of the bright and cold surface. To help quantify their uncertainties, single-layered overcast liquid-phase Arctic stratus cloud microphysical properties retrieved by using the Clouds and the Earth's Radiant Energy System Edition 2 and Edition 4 (CERES Ed2 and Ed4) algorithms are compared with ground-based retrievals at the Atmospheric Radiation Measurement North Slope of Alaska (ARM NSA) site at Barrow, AK, during the period from March 2000 to December 2006. A total of 206 and 140 snow-free cases (Rsfc ≤ 0.3), and 108 and 106 snow cases (Rsfc > 0.3), respectively, were selected from Terra and Aqua satellite passes over the ARM NSA site. The CERES Ed4 and Ed2 optical depth (τ) and liquid water path (LWP) retrievals from both Terra and Aqua are almost identical and have excellent agreement with ARM retrievals under snow-free and snow conditions. In order to reach a radiation closure study for both the surface and top of atmosphere (TOA) radiation budgets, the ARM precision spectral pyranometer-measured surface albedos were adjusted (63.6% and 80% of the ARM surface albedos for snow-free and snow cases, respectively) to account for the water and land components of the domain of 30 km × 30 km. Most of the radiative transfer model calculated SW↓sfc and SW↑TOA fluxes by using ARM and CERES cloud retrievals and the domain mean albedos as input agree with the ARM and CERES flux observations within 10 W m-2 for both snow-free and snow conditions. Sensitivity studies show that the ARM LWP and re retrievals are less dependent on solar zenith angle (SZA), but all retrieved optical depths increase with SZA.
On the linear properties of the nonlinear radiative transfer problem
Pikichyan, H. V.
2016-11-01
In this report, we further expose the assertions made in nonlinear problem of reflection/transmission of radiation from a scattering/absorbing one-dimensional anisotropic medium of finite geometrical thickness, when both of its boundaries are illuminated by intense monochromatic radiative beams. The new conceptual element of well-defined, so-called, linear images is noteworthy. They admit a probabilistic interpretation. In the framework of nonlinear problem of reflection/transmission of radiation, we derive solution which is similar to linear case. That is, the solution is reduced to the linear combination of linear images. By virtue of the physical meaning, these functions describe the reflectivity and transmittance of the medium for a single photon or their beam of unit intensity, incident on one of the boundaries of the layer. Thereby the medium in real regime is still under the bilateral illumination by external exciting radiation of arbitrary intensity. To determine the linear images, we exploit three well known methods of (i) 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".
Dykema, J. A.; Keith, D.; Keutsch, F. N.
2016-12-01
The deliberate modification of Earth's albedo as a complement to mitigation in order to slow climate change brings with it a range of risks. A range of different approaches have been studied, including the injection of aerosol particles into the stratosphere to decrease solar energy input into the climate system. Key side effects from this approach include ozone loss and radiative heating. Both of these side effects may produce dynamical changes with further consequences for stratospheric and tropospheric climate. Studies of past volcanic eruptions suggest that sulfate aerosol injection may be capable of achieving a compensating radiative forcing of -1 W m-2 or more. It is also expected that such injection of sulfate aerosols will result in loss of stratospheric ozone and of significant infrared heating. The problems resulting from sulfate aerosols intended have motivated the investigation of alternative materials, including high refractive index solid materials. High refractive index materials have the potential to scatter more efficiently per unit mass, leading to a reduction in surface area for heterogeneous chemistry, and, depending on details of absorption, less radiative heating. Fundamentally, assessing these trade-offs requires accurate knowledge of the complex refractive index of materials being considered over the full range of wavelengths relevant to atmospheric radiative transfer, that is, from ultraviolet to far-infrared. Our survey of the relevant literature finds that such measurements are not available for all materials of interest at all wavelengths. We utilize a method developed in astrophysics to fill in spectral gaps, and find that some materials may heat the stratosphere substantially more than was found in previous work. Stratospheric heating can warm the tropical tropopause layer, increasing the flux of water vapor into the stratosphere, with further consequences for atmospheric composition and radiative forcing. We analyze this consequence
Morales, Giovanni; Martínez, Ramiro
2009-07-30
This research's main goals were to analyze ketene dimers' relative stability and expand group additivity value (GAV) methodology for estimating the thermochemical properties of high-weight ketene polymers (up to tetramers). The CBS-Q multilevel procedure and statistical thermodynamics were used for calculating the thermochemical properties of 20 cyclic structures, such as diketenes, cyclobutane-1,3-diones, cyclobut-2-enones and pyran-4-ones, as well as 57 acyclic base compounds organized into five groups. According to theoretical heat of formation predictions, diketene was found to be thermodynamically favored over cyclobutane-1,3-dione and its enol-tautomeric form (3-hydroxycyclobut-2-enone). This result did not agree with old combustion experiments. 3-Hydroxycyclobut-2-enone was found to be the least stable dimer and its reported experimental detection in solution may have been due to solvent effects. Substituted diketenes had lower stability than substituted cyclobutane-1,3-diones with an increased number of methyl substituents, suggesting that cyclobutane-1,3-dione type dimers are the major products because of thermodynamic control of alkylketene dimerization. Missing GAVs for the ketene dimers and related structures were calculated through linear regression on the 57 acyclic base compounds. Corrections for non next neighbor interactions (such as gauche, eclipses, and internal hydrogen bond) were needed for obtaining a highly accurate and precise regression model. To the best of our knowledge, the hydrogen bond correction for GAV methodology is the first reported in the literature; this correction was correlated to MP2/6-31Gdagger and HF/6-31Gdagger derived geometries to facilitate its application. GAVs assessed by the linear regression model were able to reproduce acyclic compounds' theoretical thermochemical properties and experimental heat of formation for acetylacetone. Ring formation and substituent position corrections were calculated by consecutively
Wave field synthesis of moving virtual sound sources with complex radiation properties.
Ahrens, Jens; Spors, Sascha
2011-11-01
An approach to the synthesis of moving virtual sound sources with complex radiation properties in wave field synthesis is presented. The approach exploits the fact that any stationary sound source of finite spatial extent radiates spherical waves at sufficient distance. The angular dependency of the radiation properties of the source under consideration is reflected by the amplitude and phase distribution on the spherical wave fronts. The sound field emitted by a uniformly moving monopole source is derived and the far-field radiation properties of the complex virtual source under consideration are incorporated in order to derive a closed-form expression for the loudspeaker driving signal. The results are illustrated via numerical simulations of the synthesis of the sound field of a sample moving complex virtual source.
Calculation of Electronic and Optical Properties of Doped Titanium Dioxide Nanostructure
Directory of Open Access Journals (Sweden)
Sh. Khaleghi
2012-06-01
Full Text Available By means of first principles calculations we show that both rutile and anatase phases of bulk TiO2 doped by S, Se or Pb can display substantial decreasing in the band gap (up to 50%, while doping by Zr does not sizably affect the band-gap value. Moreover, the absorption edge is shifted (up to 1 eV to the lower energy range in the case of TiO2 doped by S or Pb that opens a way to enhancing of absorption of sun’s radiation. We also discuss how our findings can improve efficiency of photovoltaic cells and photocatalytic cells for hydrogen generation.
Defect properties of CuCrO2: A density functional theory calculation
Institute of Scientific and Technical Information of China (English)
Fang Zhi-Jie; Zhu Ji-Zhen; Zhou Jiang; Mo Man
2012-01-01
Using the first-principles methods,we study the formation energetics properties of intrinsic defects,and the charge doping properties of extrinsic defects in transparent conducting oxides CuCrO2.Intrinsic defects,some typical acceptortype,and donor-type extrinsic defects in their relevant charge state are considered.By systematically calculating the formation energies and transition energy,the results of calculation show that,Vcu,Oi,and OCu are the relevant intrinsic defects in CuCrO2; among these intrinsic defects,VCu is the most efficient acceptor in CuCrO2.It is found that all the donor-type extrinsic defects have difficulty in inducing n-conductivity in CuCrO2 because of their deep transition energy level.For all the acceptor-type extrinsic defects,substituting Mg for Cr is the most prominent doping acceptor with relative shallow transition energy levels in CuCrO2.Our calculation results are expected to be a guide for preparing promising n-type and p-type materials in CuCrO2.
Molecular dynamics calculation of thermophysical properties for a highly reactive liquid.
Wang, H P; Luo, B C; Wei, B
2008-10-01
In order to further understand the physical characteristics of liquid silicon, the thermophysical properties are required over a broad temperature range. However, its high reactivity brings about great difficulties in the experimental measurement. Here we report the thermophysical properties by molecular dynamics calculation, including density, specific heat, diffusion coefficient, and surface tension. The calculation is performed with a system consisting of 64,000 atoms, and employing the Stillinger-Weber (SW) potential model and the modified embedded atom method (MEAM) potential model. The results show that the density increases as a quadratic function of undercooling, and the value calculated by SW potential model is only 2-4 % smaller than the reported experimental data. The specific heat is obtained to be 30.95 J mol;{-1}K;{-1} by SW potential model and 32.50 J mol;{-1}K;{-1} by MEAM potential model, both of which are constants in the corresponding ranges of temperature. The self-diffusion coefficient is exponentially dependent on the temperature and consistent with the Arrhenius equation. The surface tension increases linearly with the rise of undercooling and agrees well with the reported experimental results. This work provides reasonable data in much wider temperature range, especially for the undercooled metastable state.
First principles calculation of thermo-mechanical properties of thoria using Quantum ESPRESSO
Malakkal, Linu; Szpunar, Barbara; Zuniga, Juan Carlos; Siripurapu, Ravi Kiran; Szpunar, Jerzy A.
2016-05-01
In this work, we have used Quantum ESPRESSO (QE), an open source first principles code, based on density-functional theory, plane waves, and pseudopotentials, along with quasi-harmonic approximation (QHA) to calculate the thermo-mechanical properties of thorium dioxide (ThO2). Using Python programming language, our group developed qe-nipy-advanced, an interface to QE, which can evaluate the structural and thermo-mechanical properties of materials. We predicted the phonon contribution to thermal conductivity (kL) using the Slack model. We performed the calculations within local density approximation (LDA) and generalized gradient approximation (GGA) with the recently proposed version for solids (PBEsol). We employed a Monkhorst-Pack 5 × 5 × 5 k-points mesh in reciprocal space with a plane wave cut-off energy of 150 Ry to obtain the convergence of the structure. We calculated the dynamical matrices of the lattice on a 4 × 4 × 4 mesh. We have predicted the heat capacity, thermal expansion and the phonon contribution to thermal conductivity, as a function of temperature up to 1400K, and compared them with the previous work and known experimental results.
Nagabalasubramanian, P B; Periandy, S; Karabacak, Mehmet; Govindarajan, M
2015-06-15
The solid phase FT-IR and FT-Raman spectra of 4-vinylcyclohexene (abbreviated as 4-VCH) have been recorded in the region 4000-100cm(-1). The optimized molecular geometry and vibrational frequencies of the fundamental modes of 4-VCH have been precisely assigned and analyzed with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method at 6-311++G(d,p) level basis set. The theoretical frequencies were properly scaled and compared with experimentally obtained FT-IR and FT-Raman spectra. Also, the effect due the substitution of vinyl group on the ring vibrational frequencies was analyzed and a detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated total energy distribution (TED). The time dependent DFT (TD-DFT) method was employed to predict its electronic properties, such as electronic transitions by UV-Visible analysis, HOMO and LUMO energies, molecular electrostatic potential (MEP) and various global reactivity and selectivity descriptors (chemical hardness, chemical potential, softness, electrophilicity index). Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Atomic charges obtained by Mulliken population analysis and NBO analysis are compared. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures are also calculated.
Energy Technology Data Exchange (ETDEWEB)
Miranda, Fabio S.; Ronconi, Celia M.; Sousa, Mikaelly O.B.; Silveira, Gleiciani Q.; Vargas, Maria D., E-mail: miranda@vm.uff.br, E-mail: mdvargascp@gmail.com [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Quimica
2014-01-15
Four novel 6-aminocoumarin-naphthoquinone conjugates were synthesized and their photophysical and electrochemical properties, investigated. 2-Chloro-3-(2-oxo-2H-chromen-6- ylamino)-1,4-naphthoquinone 1 did not present appreciable fluorescence in solution in comparison with 6-aminocoumarin, 6-AC. In order to understand the reasons for the fluorescence quenching in this compound, two strategies were attempted. Firstly, compound 1 was N-methylated to remove the intramolecular N-H...O=C electrostatic interaction that maintained the two units fixed, but the emission properties of the product 2 were not significantly different from those of 1. Time-dependent density functional theory (TD-DFT) calculations of compounds 1 and 2 indicate that the fluorescence quenching is related to the electron acceptor character of the naphthoquinone ring. The second strategy, therefore, involved the substitution of the chlorine atom in position 2 of the naphthoquinone nucleus for different electron donor groups (compounds 3-5), but again the emission properties did not change significantly. To explain these experimental findings, TD-DFT calculations of the ground (S{sub 0}) and excited (S{sub 1}) states of all molecules in solution were carried out. The results suggest that the energy states in these conjugates are such that the fluorescent group (6-AC) donates electrons to the naphthoquinone LUMO resulting in an oxidative photoinduced electron transfer (oxidative-PET). (author)
Directory of Open Access Journals (Sweden)
D. Topping
2015-11-01
Full Text Available In this paper we describe the development and application of a new web based facility, UManSysProp (http://umansysprop.seaes.manchester.ac.uk, for automating predictions of molecular and atmospheric aerosol properties. Current facilities include: pure component vapour pressures, critical properties and sub-cooled densities of organic molecules; activity coefficient predictions for mixed inorganic–organic liquid systems; hygroscopic growth factors and CCN activation potential of mixed inorganic/organic aerosol particles; absorptive partitioning calculations with/without a treatment of non-ideality. The aim of this new facility is to provide a single point of reference for all properties relevant to atmospheric aerosol that have been checked for applicability to atmospheric compounds where possible. The group contribution approach allows users to upload molecular information in the form of SMILES strings and UManSysProp will automatically extract the relevant information for calculations. Built using open source chemical informatics, and hosted at the University of Manchester, the facilities are provided via a browser and device-friendly web-interface, or can be accessed using the user's own code via a JSON API. In this paper we demonstrate its use with specific examples that can be simulated using the web-browser interface.
Calculation of effective transport properties of partially saturated gas diffusion layers
Bednarek, Tomasz; Tsotridis, Georgios
2017-02-01
A large number of currently available Computational Fluid Dynamics numerical models of Polymer Electrolyte Membrane Fuel Cells (PEMFC) are based on the assumption that porous structures are mainly considered as thin and homogenous layers, hence the mass transport equations in structures such as Gas Diffusion Layers (GDL) are usually modelled according to the Darcy assumptions. Application of homogenous models implies that the effects of porous structures are taken into consideration via the effective transport properties of porosity, tortuosity, permeability (or flow resistance), diffusivity, electric and thermal conductivity. Therefore, reliable values of those effective properties of GDL play a significant role for PEMFC modelling when employing Computational Fluid Dynamics, since these parameters are required as input values for performing the numerical calculations. The objective of the current study is to calculate the effective transport properties of GDL, namely gas permeability, diffusivity and thermal conductivity, as a function of liquid water saturation by using the Lattice-Boltzmann approach. The study proposes a method of uniform water impregnation of the GDL based on the "Fine-Mist" assumption by taking into account the surface tension of water droplets and the actual shape of GDL pores.
Multivariate statics employed as proposal for calculating the market value and property taxation
Directory of Open Access Journals (Sweden)
Jonilson Heil
2013-05-01
Full Text Available It is well known that the Brazilian municipalities aim to increase their own revenues and reduce dependence on state and federal financial transfers, optimizing their tax revenues. It is also known that the municipalities intend to carry out that mission with integrity, clarity and to present easily the accountability to regulators, as well as to their respective populations. In this paper carried out a study on the methodology employed in a town in central-southern state of Paraná to calculate the venal values and property tax (IPTU and the consequent taxation of IPTU and ITBI in these goods. Based on municipality registration data was developed, by means of multivariate statistical techniques, an analysis of the characteristics that most influence the monetary valuations of the property, and applying multiple linear regression analysis are proposed models to estimate values of the venal values of properties, allowing tax calculations predict through it. Finally, comparisons are presented between the results from the methodology used by the municipality with those obtained by the models developed, proposed for use in general.
Structures, phase transitions, and magnetic properties of C o3Si from first-principles calculations
Zhao, Xin; Yu, Shu; Wu, Shunqing; Nguyen, Manh Cuong; Wang, Cai-Zhuang; Ho, Kai-Ming
2017-07-01
C o3Si was recently reported to exhibit remarkable magnetic properties in the nanoparticle form [B. Balasubramanian et al., Appl. Phys. Lett. 108, 152406 (2016)], 10.1063/1.4945987, yet better understanding of this material should be promoted. Here we report a study on the crystal structures of C o3Si using an adaptive genetic algorithm and discuss its electronic and magnetic properties from first-principles calculations. Several competing phases of C o3Si have been revealed from our calculations. We show that the hexagonal C o3Si structure reported in experiments has lower energy in the nonmagnetic state than in the ferromagnetic state at zero temperature. The ferromagnetic state of the hexagonal structure is dynamically unstable with imaginary phonon modes and transforms into a new orthorhombic structure, which is confirmed by our structure searches to have the lowest energy for both C o3Si and C o3Ge . Magnetic properties of the experimental hexagonal structure and the lowest-energy structures obtained from our structure searches are investigated in detail.
Attenuation properties of cement composites: Experimental measurements and Monte Carlo calculations
Florez Meza, Raul Fernando
Developing new cement based materials with excellent mechanical and attenuation properties is critically important for both medical and nuclear power industries. Concrete continues to be the primary choice material for the shielding of gamma and neutron radiation in facilities such as nuclear reactors, nuclear waste repositories, spent nuclear fuel pools, heavy particle radiotherapy rooms, particles accelerators, among others. The purpose of this research was to manufacture cement pastes modified with magnetite and samarium oxide and evaluate the feasibility of utilizing them for shielding of gamma and neutron radiation. Two different experiments were conducted to accomplish these goals. In the first one, Portland cement pastes modified with different loading of fine magnetite were fabricated and investigated for application in gamma radiation shielding. The experimental results were verified theoretically through XCOM and the Monte Carlo N-Particle (MCNP) transport code. Scanning electron microscopy and x-ray diffraction tests were used to investigate the microstructure of the samples. Mechanical characterization was also perfornmed by compression testing. The results suggest that fine magnetite is a suitable aggregate for increasing the compressive and flexural strength of white Portland cement pastes; however, there is no improvement of the attenuation at intermediate energy (662 keV). For the second experiment, cement pastes with different concentrations of samarium oxide were fabricated and tested for shielding against thermal neutrons. MCNP simulations were used to validate the experimental work. The result shows that samarium oxide increases the effective thermal cross section of Portland cement and has the potential to replace boron bearing compounds currently used in neutron shielding.
American Society for Testing and Materials. Philadelphia
1988-01-01
1.1 This practice describes the calculation of luminous (photometric) transmittance and reflectance of materials from spectral radiant transmittance and reflectance data obtained from Test Method E 903. 1.2 Determination of luminous transmittance by this practice is preferred over measurement of photometric transmittance by methods using the sun as a source and a photometer as detector except for transmitting sheet materials that are inhomogeneous, patterned, or corrugated. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Legrand, M.; Dubovik, O.; Lapyonok, T.; Derimian, Y.
2014-12-01
Spectral radiative parameters (extinction optical depth, single scattering albedo, asymmetry factor) of spheroids of mineral dust composed of quartz and clays have been simulated at wavelengths between 7.0 and 10.2 μm using a T-matrix code. In spectral intervals with high values of complex index of refraction and for large particles, the parameters cannot be fully calculated with the code. Practically, the calculations are stopped at a truncation radius over which the particles contribution cannot thus be taken into account. To deal with this issue, we have developed and applied an accurate corrective technique of T-matrix Size Truncation Compensation (TSTC). For a mineral dust described by its AERONET standard aspect ratio (AR) distribution, the full error margin when applying the TSTC is within 0.3% (or ±0.15%), whatever the radiative parameter and the wavelength considered, for quartz (the most difficult case). Large AR values limit also the possibilities of calculation with the code. The TSTC has been able to complete the calculations of the T-matrix code for a modified AERONET AR distribution with a maximum AR of 4.7 instead of 3 for the standard distribution. Comparison between the simulated properties of spheroids and of spheres of same volume confirms, in agreement with the literature, that significant differences are observed in the vicinity of the mineral resonant peaks (λ ca. 8.3-8.7 μm for quartz, ca. 9.3-9.5 μm for clays) and that they are due to absorption by the small particles. This is a favorable circumstance for the TSTC, which is concerned with the contribution of the largest particles. This technique of numerical calculation improves the accuracy of the simulated radiative parameters of mineral dust, which must lead to a progress in view of applications such as remote sensing or determination of energy balance of dust in the thermal infrared (TIR), incompletely investigated so far.
Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Zhao, Xin; Ke, Liqin; Nguyen, Manh Cuong; Wang, Cai-Zhuang, E-mail: wangcz@ameslab.gov; Ho, Kai-Ming, E-mail: kmh@ameslab.gov [Ames Laboratory, U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)
2015-06-28
The structures and magnetic properties of Co-Zr-B alloys near the composition of Co{sub 5}Zr with B at. % ≤6% were studied using adaptive genetic algorithm and first-principles calculations. The energy and magnetic moment contour maps as a function of chemical composition were constructed for the Co-Zr-B magnet alloys through extensive structure searches and calculations. We found that Co-Zr-B system exhibits the same structure motif as the “Co{sub 11}Zr{sub 2}” polymorphs, and such motif plays a key role in achieving strong magnetic anisotropy. Boron atoms were found to be able to substitute cobalt atoms or occupy the “interruption” sites. First-principles calculations showed that the magnetocrystalline anisotropy energies of the boron-doped alloys are close to that of the high-temperature rhombohedral Co{sub 5}Zr phase and larger than that of the low-temperature Co{sub 5.25}Zr phase. Our calculations provide useful guidelines for further experimental optimization of the magnetic performances of these alloys.
Optical properties of the PANDA barrel DIRC radiator bars
Energy Technology Data Exchange (ETDEWEB)
Kalicy, Grzegorz; Krebs, Marvin; Peters, Klaus [GSI, Darmstadt (Germany); Goethe Universitaet, Frankfurt (Germany); Schwarz, Carsten; Schwiening, Jochen [GSI, Darmstadt (Germany); Collaboration: PANDA-Collaboration
2015-07-01
The PANDA experiment at the Facility for Antiproton and Ion Research in Europe (FAIR) at GSI, Darmstadt, will study fundamental questions of hadron physics and QCD. A fast focusing DIRC (Detection of Internally Reflected Cherenkov light) counter will provide hadronic particle identification (PID) in the barrel region of the PANDA detector. To meet the PID requirements, the Barrel DIRC has to provide precise measurements of the Cherenkov angle, which is conserved for Cherenkov photons propagating through the radiator by total internal reflection. The radiators, rectangular bars made from fused silica, have to fulfill very strict optical and mechanical requirements. This includes the squareness and parallelism of the sides of the bars, sharp corners, and a very smooth surface polish, ensuring that the Cherenkov photons reach the optical sensors without angular distortions. Currently the Barrel DIRC is at the final design stage and several different bar shapes and fabrication methods are being considered for the final detector. An optical setup, consisting of a computer-controlled positioning and a multi-wavelength laser system, is used to evaluate the radiator bars to obtain critical values like transmittance and reflectivity. The current results and techniques are presented on this poster.
Ab initio calculations on the magnetic properties of transition metal complexes
Energy Technology Data Exchange (ETDEWEB)
Bodenstein, Tilmann; Fink, Karin [Karlsruhe Institute of Technology, Institute of Nanotechnology, POB 3640, 76021 Karlsruhe (Germany)
2015-12-31
We present a protocol for the ab initio determination of the magnetic properties of mono- and polynuclear transition metal compounds. First, we obtain the low lying electronic states by multireference methods. Then, we include spin-orbit coupling and an external magnetic field for the determination of zero-field splitting and g-tensors. For the polynuclear complexes the magnetic exchange coupling constants are determined by a modified complete active space self consistent field method. Based on the results of the ab initio calculations, magnetic data such as magnetic susceptibility or magnetization are simulated and compared to experimental data. The results obtained for the polynuclear complexes are further analysed by calculations on model complexes where part of the magnetic centers are substituted by diamagnetic ions. The methods are applied to different Co and Ni containing transition metal complexes.
Li, Xinting; Zhang, Xinyu; Qin, Jiaqian; Zhang, Suhong; Ning, Jinliang; Jing, Ran; Ma, Mingzhen; Liu, Riping
2014-11-01
The structural stability and mechanical properties of WC in WC-, MoC- and NaCl-type structures under high pressure are investigated systematically by first-principles calculations. The calculated equilibrium lattice constants at zero pressure agree well with available experimental and theoretical results. The formation enthalpy indicates that the most stable WC is in WC-type, then MoC-type finally NaCl-type. By the elastic stability criteria, it is predicted that the three structures are all mechanically stable. The elastic constants Cij, bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν of the three structures are studied in the pressure range from 0 to 100 GPa. Furthermore, by analyzing the B/G ratio, the brittle/ductile behavior under high pressure is assessed. Moreover, the elastic anisotropy of the three structures up to 100 GPa is also discussed in detail.
High-pressure elastic properties of cubic Ir2P from ab initio calculations
Sun, Xiao-Wei; Bioud, Nadhira; Fu, Zhi-Jian; Wei, Xiao-Ping; Song, Ting; Li, Zheng-Wei
2016-10-01
A study of the high-pressure elastic properties of new synthetic Ir2P in the anti-fluorite structure is conducted using ab initio calculations based on density functional theory. The elastic constants C11, C12 and C44 for the cubic Ir2P are obtained by the stress-strain method and the elastic stability calculations under pressure indicate that it is stable at least 100 GPa. Additionally, the electronic density of states, the aggregate elastic moduli, that is bulk modulus, shear modulus, and Young's modulus along with the Debye temperature, Poisson's ratio, and elastic anisotropy factor are all successfully obtained. Moreover, the pressure dependence of the longitudinal and shear wave velocities in three different directions [100], [110], and [111] for Ir2P are also predicted for the first time.
Energy Technology Data Exchange (ETDEWEB)
Feldman, J.L.; Broughton, J.Q. (Complex Systems Theory Branch, Naval Research Laboratory, Washington, D.C. 20375-5000 (US)); Wooten, F. (Department of Applied Science, University of California at Davis/Livermore, Livermore, California 94550 (US))
1991-01-15
Calculations, based on the Stillinger-Weber (SW) interatomic-potential model and the method of long waves, are presented for the elastic properties of amorphous Si ({ital a}-Si) and for pressure derivatives of the elastic constants of crystalline Si. Several models of {ital a}-Si, relaxed on the basis of the SW potential, are considered, and the external stresses that are associated with these models are evaluated using the Born-Huang relations. The elastic constants appear to obey the isotropy conditions to within a reasonable accuracy and are also consistent with other predictions based on the SW potential at finite temperature obtained by Kluge and Ray. Estimates of the pressure dependence of the elastic constants, Debye temperature, and Grueeisen parameter for {ital a}-Si are also provided on the basis of these calculations.
Mihaila, Bogdan; Heisenberg, Jochen
2000-04-01
We continue the investigations of ground state properties of closed-shell nuclei using the Argonne v18 realistic NN potential, together with the Urbana IX three-nucleon interaction. The ground state wave function is used to calculate the charge form factor and charge density. Starting with the ground state wave function of the closed-shell nucleus, we use the equation of motion technique to calculate the ground state and excited states of a neighboring nucleus. We then generate the corresponding magnetic form factor. We correct for distortions due to the interaction between the electron probe and the nuclear Coulomb field using the DWBA picture. We compare our results with the available experimental data. Even though our presentation will focus mainly on the ^16O and ^15N nuclei, results for other nuclei in the p and s-d shell will also be presented.
Synthesis, characterization and DFT calculations of electronic and optical properties of YbPO4
Khadraoui, Z.; Horchani-Naifer, K.; Ferhi, M.; Ferid, M.
2015-08-01
YbPO4 crystals were synthesized by solid-state reaction and characterized by X-ray diffraction, infrared and Raman spectroscopies. The electronic structure and optical properties of YbPO4 such as the energy band structures, density of states and chemical bonds were calculated with the Density Functional Theory (DFT) for the first time. We present a combination of the GGA and the LDA + U approaches in order to obtain appropriate results due to the strong Coulomb repulsion between the highly localized 4f electrons of rare earth atoms. The linear photon-energy-dependent dielectric functions, conductivity and some optical constants such as refractive index, reflectivity and absorption coefficients were determined. The calculated total and partial densities of states indicate that the top of valance band is built upon O-2p states with P-3p states via σ (P-O) interactions, and the conduction bands mostly originate from Yb-5d states.
Energy Technology Data Exchange (ETDEWEB)
Cunliffe, Alexandra R.; Armato, Samuel G.; White, Bradley; Justusson, Julia [Department of Radiology, The University of Chicago, 5841 South Maryland Avenue, Chicago, Illinois 60637 (United States); Contee, Clay; Malik, Renuka; Al-Hallaq, Hania A., E-mail: hal-hallaq@radonc.uchicago.edu [Department of Radiation and Cellular Oncology, The University of Chicago, 5841 South Maryland Avenue, Chicago, Illinois 60637 (United States)
2015-01-15
Purpose: To characterize the effects of deformable image registration of serial computed tomography (CT) scans on the radiation dose calculated from a treatment planning scan. Methods: Eighteen patients who received curative doses (≥60 Gy, 2 Gy/fraction) of photon radiation therapy for lung cancer treatment were retrospectively identified. For each patient, a diagnostic-quality pretherapy (4–75 days) CT scan and a treatment planning scan with an associated dose map were collected. To establish correspondence between scan pairs, a researcher manually identified anatomically corresponding landmark point pairs between the two scans. Pretherapy scans then were coregistered with planning scans (and associated dose maps) using the demons deformable registration algorithm and two variants of the Fraunhofer MEVIS algorithm (“Fast” and “EMPIRE10”). Landmark points in each pretherapy scan were automatically mapped to the planning scan using the displacement vector field output from each of the three algorithms. The Euclidean distance between manually and automatically mapped landmark points (d{sub E}) and the absolute difference in planned dose (|ΔD|) were calculated. Using regression modeling, |ΔD| was modeled as a function of d{sub E}, dose (D), dose standard deviation (SD{sub dose}) in an eight-pixel neighborhood, and the registration algorithm used. Results: Over 1400 landmark point pairs were identified, with 58–93 (median: 84) points identified per patient. Average |ΔD| across patients was 3.5 Gy (range: 0.9–10.6 Gy). Registration accuracy was highest using the Fraunhofer MEVIS EMPIRE10 algorithm, with an average d{sub E} across patients of 5.2 mm (compared with >7 mm for the other two algorithms). Consequently, average |ΔD| was also lowest using the Fraunhofer MEVIS EMPIRE10 algorithm. |ΔD| increased significantly as a function of d{sub E} (0.42 Gy/mm), D (0.05 Gy/Gy), SD{sub dose} (1.4 Gy/Gy), and the algorithm used (≤1 Gy). Conclusions: An
Effect of gamma radiation on optical and electrical properties of tellurium dioxide thin films
Indian Academy of Sciences (India)
T K Maity; S L Sharma
2008-11-01
Gamma radiation induced changes in the optical and electrical properties of tellurium dioxide (TeO2) thin films, prepared by thermal evaporation, have been studied in detail. The optical characterization of the as-deposited thin films and that of the thin films exposed to various levels of gamma radiation dose clearly show that the optical bandgap decreases with increase in the gamma radiation dose up to a certain dose. At gamma radiation doses above this value, however, the optical bandgap has been found to increase. On the other hand, the current vs voltage plots for the as-deposited thin films and those for the thin films exposed to various levels of gamma radiation dose show that the current increases with the gamma radiation dose up to a certain dose and that the value of this particular dose depends upon the thickness of the film. The current has, however, been found to decrease with further increase in gamma radiation dose. The observed changes in both the optical and electrical properties indicate that TeO2 thin films can be used as the real time gamma radiation dosimeter up to a certain dose, a quantity that depends upon the thickness of the film.
Shielding properties of a conducting bar calculated with a boundary integral method
Directory of Open Access Journals (Sweden)
L. O. Fichte
2005-01-01
Full Text Available A plane rectangular bar of conducting and permeable material is placed in an external low-frequency magnetic field. The shielding properties of this object are investigated by solving the given plane eddy current problem for the vector potential with the boundary integral equation method. The vector potential inside the rectangle is governed by Helmholtz' equation, which in our case is solved by separation. The solution is inserted into the remaining boundary integral equation for the exterior vector potential in the domain surrounding the bar. By expressing its logarithmic kernel as a Fourier integral the overall solution inside and outside the bar is calculated using analytical means only.
Elastic and thermodynamic properties of c-BN from first-principles calculations
Institute of Scientific and Technical Information of China (English)
Hao Yan-Jun; Cheng Yan; Wang Yan-Ju; Chen Xiang-Rong
2007-01-01
The elastic constants and thermodynamic properties of c-BN are calculated using the first-principles plane wave method with the relativistic analytic pseudopotential of the Hartwigen, Goedecker and Hutter (HGH) type in the frame of local density approximation and using the quasi-harmonic Debye model, separately. Moreover, the dependences of the normalized volume V/V0 on pressure P, as well as the bulk modulus B, the thermal expansion α, and the heat capacity CV on pressure P and temperature T are also successfully obtained.
Directory of Open Access Journals (Sweden)
Yuriy Natanzon
2008-01-01
Full Text Available We report ﬁrst principles calculations of the electronic and elastic properties of yttriastabilized tetragonal zirconium dioxide doped with metal oxides like: GeO2, TiO2, SiO2,MgO and Al2O3. It is shown that addition of such dopants aﬀects selected elastic propertiesof ZrO2, which is driven by the attraction of electron density by dopant atom and creationof stronger dopant–oxygen bonds. This eﬀect contributes to the increase of superplasticityof doped material.
Energy levels and radiative data for Kr-like W38+ from MCDHF and RMBPT calculations
Guo, XueLing; Grumer, Jon; Brage, Tomas; Si, Ran; Chen, ChongYang; Jönsson, Per; Wang, Kai; Yan, Jun; Hutton, Roger; Zou, YaMing
2016-07-01
Energies, transition rates, line strengths and lifetimes have been computed for all levels of the 4p 6 and 4p 54d configurations of W38+ by using the multi-configuration Dirac-Hartree-Fock (MCDHF) method as well as relativistic many-body perturbation theory. We investigate systematically correlation, relativistic and quantum electro-dynamical (QED) effects of different properties, including excitation energies and transition rates. We demonstrate that it is important to include the core-valence correlation of rather deep subshells (including 3d and 3p) to reach close to spectroscopic accuracy for the transition energies. We also show that high-multipole transitions (E3, M2) are important for the lifetime of some metastable levels of 4p 54d ({}3{F}3,{}1{D}2,{}3{D}2). The present results are in good agreement with experiments and of considerably higher accuracy than those achieved in previous theoretical works.
Yang, Hua
2012-01-01
Electronic structure and optical properties of α-FeMO 3 systems (M = Sc, Ti, V, Cr, Cu, Cd or In) have been investigated using first principles calculations. All of the FeMO 3 systems have a large net magnetic moment. The ground state of pure α-Fe 2O 3 is an antiferromagnetic insulator. For M = Cu or Cd, the systems are half-metallic. Strong absorption in the visible region can be observed in the Cu and Cd-doped systems. Systems with M = Sc, Ti, V, Cr or In are not half-metallic and are insulators. The strongest peaks shift toward shorter wavelengths in the absorption spectra. It is concluded that transition metal doping can modify the electronic structure and optical properties of α-FeMO 3 systems. This journal is © 2012 The Royal Society of Chemistry.
Directory of Open Access Journals (Sweden)
A A Shokri
2013-10-01
Full Text Available In this paper, we have investigated the spin-dependent transport properties and electron entanglement in a mesoscopic system, which consists of two semi-infinite leads (as source and drain separated by a typical quantum wire with a given potential. The properties studied include current-voltage characteristic, electrical conductivity, Fano factor and shot noise, and concurrence. The calculations are based on the transfer matrix method within the effective mass approximation. Using the Landauer formalism and transmission coefficient, the dependence of the considered quantities on type of potential well, length and width of potential well, energy of transmitted electron, temperature and the voltage have been theoretically studied. Also, the effect of the above-mentioned factors has been investigated in the nanostructure. The application of the present results may be useful in designing spintronice devices.
Phase transition and thermodynamic properties of SrS via first-principles calculations
Institute of Scientific and Technical Information of China (English)
Cheng Yan; Lu Lai-Yu; Jia Ou-He; Chen Xiang-Rong
2008-01-01
The phase transition of SrS from NaG1 structure (B1) to CsCl structure (B2) is investigated by means of ab initio plane-wave pseudopotential density functional theory, and the thermodynamic properties of the B1 and the B2 structures are obtained through the quasi-harmonic Debye model. It is found that the transition phase from the B1 to the B2 structures occurs at 17.9 GPa, which is in good agreement with experimental data and other calculated results.Moreover, the thermodynamic properties (including specific heat capacity, the Debye temperature, thermal expansion and Grüneisen parameter) have also been obtained successfully.
AB INITIO CALCULATION OF THE ELASTIC AND OPTICAL PROPERTIES OF AL3SC COMPOUND
Institute of Scientific and Technical Information of China (English)
M. Song; D.H. Xiao
2007-01-01
The ab initio method has been performed to explore the elastic and optical properties of Al3Sccompound, based on a plane wave pseudopotential method. It can be seen that the calculatedequilibrium lattice parameter and elastic constants are in reasonable agreement with the previousexperimental data. The elastic constants satisfy the requirement for mechanical stability in the cubicstructure of the Al3Sc compound. The optical property calculations show that a strong absorptivepeak exists from 0-15eV and a relative small absorptive peak exists around 30eV. The form iscaused by the optical transitions between high s, p, and d bands, and the latter results from theoptical transitions from high s, p, and d bands to the low 2p band.
Directory of Open Access Journals (Sweden)
J. Hsu
2017-07-01
Full Text Available Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18–0.8 µm region. The Cloud-J core consists of an eight-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. Cloud-J uses cloud quadrature to accurately average over correlated cloud layers. It uses the scattering phase function of aerosols and clouds expanded to eighth order and thus avoids isotropic-equivalent approximations prevalent in most solar heating codes. The spectral extension from 0.8 to 12 µm enables calculation of both scattered and absorbed sunlight and thus aerosol direct radiative effects and heating rates throughout the Earth's atmosphere.The Solar-J extension adopts the correlated-k gas absorption bins, primarily water vapor, from the shortwave Rapid Radiative Transfer Model for general circulation model (GCM applications (RRTMG-SW. Solar-J successfully matches RRTMG-SW's tropospheric heating profile in a clear-sky, aerosol-free, tropical atmosphere. We compare both codes in cloudy atmospheres with a liquid-water stratus cloud and an ice-crystal cirrus cloud. For the stratus cloud, both models use the same physical properties, and we find a systematic low bias of about 3 % in planetary albedo across all solar zenith angles caused by RRTMG-SW's two-stream scattering. Discrepancies with the cirrus cloud using any of RRTMG-SW's three different parameterizations are as large as about 20–40 % depending on the solar zenith angles and occur throughout the atmosphere.Effectively, Solar-J has combined the best components of RRTMG-SW and Cloud-J to build a high-fidelity module for the scattering and absorption of sunlight in the Earth's atmosphere, for which the three major components – wavelength
Hsu, Juno; Prather, Michael J.; Cameron-Smith, Philip; Veidenbaum, Alex; Nicolau, Alex
2017-07-01
Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18-0.8 µm region. The Cloud-J core consists of an eight-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. Cloud-J uses cloud quadrature to accurately average over correlated cloud layers. It uses the scattering phase function of aerosols and clouds expanded to eighth order and thus avoids isotropic-equivalent approximations prevalent in most solar heating codes. The spectral extension from 0.8 to 12 µm enables calculation of both scattered and absorbed sunlight and thus aerosol direct radiative effects and heating rates throughout the Earth's atmosphere.The Solar-J extension adopts the correlated-k gas absorption bins, primarily water vapor, from the shortwave Rapid Radiative Transfer Model for general circulation model (GCM) applications (RRTMG-SW). Solar-J successfully matches RRTMG-SW's tropospheric heating profile in a clear-sky, aerosol-free, tropical atmosphere. We compare both codes in cloudy atmospheres with a liquid-water stratus cloud and an ice-crystal cirrus cloud. For the stratus cloud, both models use the same physical properties, and we find a systematic low bias of about 3 % in planetary albedo across all solar zenith angles caused by RRTMG-SW's two-stream scattering. Discrepancies with the cirrus cloud using any of RRTMG-SW's three different parameterizations are as large as about 20-40 % depending on the solar zenith angles and occur throughout the atmosphere.Effectively, Solar-J has combined the best components of RRTMG-SW and Cloud-J to build a high-fidelity module for the scattering and absorption of sunlight in the Earth's atmosphere, for which the three major components - wavelength integration, scattering, and
Directory of Open Access Journals (Sweden)
C. Lund Myhre
2007-11-01
Full Text Available In spring 2006 a special meteorological situation occurred in the European Arctic region giving record high levels of air pollution. The synoptic situation resulted in extensive transport of pollution predominantly from agricultural fires in Eastern Europe into the Arctic region and record high air-pollution levels were measured at the Zeppelin observatory at Ny-Ålesund (78°54' N, 11°53' E in the period from 25 April to 12 May. In the present study we investigate the optical properties of the aerosols from this extreme event and we estimate the radiative forcing of this episode.
We examine the aerosol optical properties from the source region and into the European Arctic and explore the evolution of the episode and the changes in the optical properties. A number of sites in Eastern Europe, Northern Scandinavia and Svalbard are included in the study. The observations show that the maximum AOD was from 2–3 May at all sites and varies from 0.52 to 0.87, and the corresponding Ångstrøm exponent was relatively large. Lidar measurements from Minsk, ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research at Andenes and Ny-Ålesund show that the aerosol layer was below 3 km at all sites the height is decreasing from the source region and into the Arctic. For the AERONET sites included (Minsk, Toravere, Hornsund we have further studied the evolution of the aerosol size. The single scattering albedo at Svalbard is provided for two sites; Ny-Ålesund and Hornsund. Importantly the calculated single scattering albedo based on the aerosol chemical composition and size distribution from Ny-Ålesund and the AERONET measurements at Hornsund are consistent. We have found strong agreement between the satellite daily MODIS AOD and the ground-based AOD observations. This agreement is crucial for accurate radiative forcing calculations. We calculate a strong negative radiative forcing for the most polluted days employing the analysed
Fisenko, Anatoliy I
2014-01-01
Using the three-component spectral model describing the FIRAS average continuum spectra, the analytical expressions for the temperature dependence of the thermodynamic and radiative functions of the galactic far-infrared radiation are obtained. The COBE FIRAS instrument data in the 0.15 - 2.88 THz frequency interval at the mean temperatures T = 17.72 K, T = 14 K, and T =6.73 K are used for calculating the radiative and thermodynamic functions, such as the total radiation power per unit area, total energy density, total emissivity, number density of photons, Helmholtz free energy density, entropy density, heat capacity at constant volume and pressure for the warm, intermediate-temperature and very cold components of the Galactic continuum spectra. The generalized Stefan-Boltzmann laws for the warm, intermediate-temperature and very cold components are constructed. This result is important when we construct the cosmological models of radiative transfer in the inner Galaxy. Within the framework of the three- com...
Energy Technology Data Exchange (ETDEWEB)
Zankl, M. [Helmholtz Zentrum Muenchen - Deutsches Forschungszentrum fuer Gesundheit und Umwelt, Muenchen (Germany). Inst fuer Strahlenschutz; Becker, J.; Petoussi-Henss, N.; Schlattl, H.
2012-02-15
Dose estimations of internal and external radiation exposure were based so far on mathematical phantoms with rather simple geometrical descriptions of the human body and teh organs. Recently the mathematical phantoms are replaced by more realistic voxel models that allow a more realistic dose estimation for professional radiation exposed personnel, individuals and patients. The projects is aimed to calculate organ doses for exposure to environmental radiation, organ doses for patients during computed tomography and to develop a voxel model for pregnant (24th week of pregnancy) woman for the estimation of radiation doses for the unborn child.
Iwabuchi, Hironobu; Saito, Masanori; Tokoro, Yuka; Putri, Nurfiena Sagita; Sekiguchi, Miho
2016-12-01
Satellite remote sensing of the macroscopic, microphysical, and optical properties of clouds are useful for studying spatial and temporal variations of clouds at various scales and constraining cloud physical processes in climate and weather prediction models. Instead of using separate independent algorithms for different cloud properties, a unified, optimal estimation-based cloud retrieval algorithm is developed and applied to moderate resolution imaging spectroradiometer (MODIS) observations using ten thermal infrared bands. The model considers sensor configurations, background surface and atmospheric profile, and microphysical and optical models of ice and liquid cloud particles and radiative transfer in a plane-parallel, multilayered atmosphere. Measurement and model errors are thoroughly quantified from direct comparisons of clear-sky observations over the ocean with model calculations. Performance tests by retrieval simulations show that ice cloud properties are retrieved with high accuracy when cloud optical thickness (COT) is between 0.1 and 10. Cloud-top pressure is inferred with uncertainty lower than 10 % when COT is larger than 0.3. Applying the method to a tropical cloud system and comparing the results with the MODIS Collection 6 cloud product shows good agreement for ice cloud optical thickness when COT is less than about 5. Cloud-top height agrees well with estimates obtained by the CO2 slicing method used in the MODIS product. The present algorithm can detect optically thin parts at the edges of high clouds well in comparison with the MODIS product, in which these parts are recognized as low clouds by the infrared window method. The cloud thermodynamic phase in the present algorithm is constrained by cloud-top temperature, which tends not to produce results with an ice cloud that is too warm and liquid cloud that is too cold.
Directory of Open Access Journals (Sweden)
A. Yu. Zhuravlev
2016-02-01
Full Text Available Purpose. The work is intended to investigate the electromagnetic processes in impedance bond in order to improve noise immunity of track circuits (TC for safe railway operation. Methodology. To achieve this purpose the methods of scientific analysis, mathematical modelling, experimental study, a large-scale simulation were used. Findings. The work examined the interference affecting the normal performance of track circuits. To a large extent, part of track circuit damages account for failures in track circuit equipment. Track circuit equipment is connected directly to the track line susceptible to traction current interference, which causes changes in its electrical characteristics and electromagnetic properties. Normal operability, performance of the main operating modes of the track circuit is determined by previous calculation of its performance and compilation of regulatory tables. The classical method for determination of track circuit parameters was analysed. The classical calculation method assumes representation of individual sections of the electrical track circuit using the quadripole network with known coefficients, usually in the A-form. Determining the coefficients of linear element circuit creates no metrological or mathematical difficulties. However, in circuits containing nonlinear ferromagnets (FM, obtaining the coefficients on the entire induction change range in the cores is quite a difficult task because the classical methods of idling (I and short circuit (SC are not acceptable. This leads to complicated methods for determining both the module and the arguments of quadripole network coefficients. Instead of the classical method, the work proposed the method for calculating the track circuit dependent on nonlinear properties of ferromagnets. Originality. The article examines a new approach to the calculation of TC taking into account the losses in ferromagnets (FM, without determination of equivalent circuit quadripole
Statistical and coherence properties of radiation from X-ray free electron lasers
Saldin, E L; Yurkov, M V
2009-01-01
We describe statistical and coherence properties of the radiation from x-ray free electron lasers (XFEL). It is shown that the X-ray FEL radiation before saturation is described with gaussian statistics. Particularly important is the case of the optimized X-ray FEL, studied in detail. Applying similarity techniques to the results of numerical simulations allowed us to find universal scaling relations for the main characteristics of an X-ray FEL operating in the saturation regime: efficiency, coherence time and degree of transverse coherence. We find that with an appropriate normalization of these quantities, they are functions of only the ratio of the geometrical emittance of the electron beam to the radiation wavelength. Statistical and coherence properties of the higher harmonics of the radiation are highlighted as well.
Zhang, X; Zhang, Xiao-he; Sutherland, Peter
1993-01-01
A new, fully dynamic and self-consistent radiation hydrodynamics code, suitable for the calculation of supernovae light curves and continuum spectra, is described. It is a multigroup (frequency-dependent) code and includes all important $O(v/c)$ effects. It is applied to the model W7 of Nomoto, Thielemann, \\& Yokoi (1984) for supernovae of type Ia. Radioactive energy deposition is incorporated through use of tables based upon Monte Carlo results. Effects of line opacity (both static or line blanketing and expansion or line blocking) are neglected, although these may prove to be important. At maximum light, models based upon different treatments of the opacity lead to values for $M_{B,max}$ in the range of -19.0 to -19.4. This range falls between the values for observed supernova claimed by Leibundgut \\& Tammann (1990) and by Pierce, Ressler, \\& Shure (1992).
Li, Changping
2015-07-22
In this letter, we propose a fast numerical solution for the steady state radiative transfer equation based on the approach in [1] in order to calculate the optical path loss of light propagation suffering from attenuation due to the absorption and scattering in various water types. We apply an optimal non-uniform method to discretize the angular space and an upwind type finite difference method to discretize the spatial space. A Gauss-Seidel iterative method is then applied to solve the fully discretized system of linear equations. Finally, we extend the resulting radiance in 2-dimensional to 3-dimensional by the azimuthal symmetric assumption to compute the received optical power under the given receiver aperture and field of view. The accuracy and efficiency of the proposed scheme are validated by uniform RTE solver and Monte Carlo simulations.
Tunable Thermal Radiative Properties of Nanotube and Nanowire Arrays
2011-06-28
Troullier–Martins pseudopotentials [13]. A primitive cell with one Ga and one As atoms and a large plane wave cutoff of 16 Hartree/Bohr are used. A 12 × 12...GaAs has a zinc-blende structure, which has only two atoms in a primitive cell and only three optical phonon branches. The calculated zone-center
Zhang, Huan; Bo, Tian-Li; Zheng, Xiaojing
2017-03-01
Dusty phenomena, such as wind-blown sand, dust devils, and dust storms, play key roles in Earth's climate and geological processes. Dust electrification considerably affects the lifting and transport of dust particles. However, the electrical properties of dust storms remain poorly understood. Here, we conducted multi-parameter measurements and theoretical calculations to investigate the electrical properties of dust storms and their application to dust storm prediction. The results show that the vertical electric field (E-field) decreases first, then increases, and finally decreases with the height above the ground, reversing its direction at two heights, ∼ 8- 12 and ∼ 24 m. This suggests that the charge polarity of dust particles changes from negative to positive and back to negative again as the height increases. By carefully analyzing the E-field and dust concentration data, we further found that there is a significant positive linear relationship between the measured E-field intensity and dust concentration at the given ambient conditions. In addition, measurements and calculations demonstrate that a substantial enhancement in the vertical E-field can be observed several hours before the arrival of the external-source dust storms, indicating that the E-field can be used to provide an early warning of external-source dust storms.
Moon, Juhyuk
2012-06-04
The structure and elasticity of tricalcium aluminate (C 3A) have been experimentally and theoretically studied. From high-pressure X-ray diffraction experiments, the bulk modulus of 102(6) and 110(3) GPa were obtained by fitting second- and third-order finite strain equation of state, respectively. First-principles calculations with a generalized gradient approximation gave an isotropic bulk modulus of 102.1 GPa and an isothermal bulk modulus of 106.0 GPa. The static calculations using the exchange-correlation functional show an excellent agreement with the experimental measurements. Based on the agreement, accurate elastic constants and other elastic moduli were computed. The slight difference of behavior at high pressure can be explained by the infiltration of pressure-transmitting silicone oil into structural holes in C 3A. The computed elastic and mechanical properties will be useful in understanding structural and mechanical properties of cementitious materials, particularly with the increasing interest in the advanced applications at the nanoscale. © 2012 The American Ceramic Society.
Ab initio calculation of structural stability, electronic and optical properties of Ag{sub 2}Se
Energy Technology Data Exchange (ETDEWEB)
Rameshkumar, S.; Jayalakshmi, V., E-mail: karthikajayam@yahoo.co.in [Department of Physics, SRM University, Ramapuram Campus, Chennai – 600089 (India); Jaiganesh, G. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Palanivel, B. [Department of Physics, Pondicherry Engineering College, Puducherry – 605014 (India)
2015-06-24
The structural stability, electronic and optical properties of Ag{sub 2}Se compound is studied using ab initio packages. Ag{sub 2}Se is found to crystallize in orthorhombic structure with two different space groups i.e. P2{sub 1}2{sub 1}2{sub 1} (No. 19) and P222{sub 1} (No. 17). For this compound in these two space groups, the total energy has been computed as a function of volume. Our calculated results suggest that the P2{sub 1}2{sub 1}2{sub 1}–phase is more stable than that of the P222{sub 1}–phase. The band structure calculation show that Ag{sub 2}Se is semimetallic with an overlap of about 0.014 eV in P2{sub 1}2{sub 1}2{sub 1}–phase whereas is metallic in nature in P222{sub 1}–phase. Moreover, the optical properties including the dielectric function, energy loss spectrum are obtained and analysed.
Energy Technology Data Exchange (ETDEWEB)
Gan, Li, E-mail: ligan0001@gmail.com; Mousen, Cheng; Xiaokang, Li [College of Aerospace Science and Engineering, National University of Defense Technology, Changsha (China)
2014-03-15
In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter.
Energy Technology Data Exchange (ETDEWEB)
Lordi, V; Aberg, D; Erhart, P; Wu, K J
2007-07-30
The development of high resolution, room temperature semiconductor radiation detectors requires the introduction of materials with increased carrier mobility-lifetime ({mu}{tau}) product, while having a band gap in the 1.4-2.2 eV range. AlSb is a promising material for this application. However, systematic improvements in the material quality are necessary to achieve an adequate {mu}{tau} product. We are using a combination of simulation and experiment to develop a fundamental understanding of the factors which affect detector material quality. First principles calculations are used to study the microscopic mechanisms of mobility degradation from point defects and to calculate the intrinsic limit of mobility from phonon scattering. We use density functional theory (DFT) to calculate the formation energies of native and impurity point defects, to determine their equilibrium concentrations as a function of temperature and charge state. Perturbation theory via the Born approximation is coupled with Boltzmann transport theory to calculate the contribution toward mobility degradation of each type of point defect, using DFT-computed carrier scattering rates. A comparison is made to measured carrier concentrations and mobilities from AlSb crystals grown in our lab. We find our predictions in good quantitative agreement with experiment, allowing optimized annealing conditions to be deduced. A major result is the determination of oxygen impurity as a severe mobility killer, despite the ability of oxygen to compensation dope AlSb and reduce the net carrier concentration. In this case, increased resistivity is not a good indicator of improved material performance, due to the concomitant sharp reduction in {mu}{tau}.
Energy Technology Data Exchange (ETDEWEB)
Strange, D. L.; Bander, T. J.
1981-04-01
The MILDOS Computer Code estimates impacts from radioactive emissions from uranium milling facilities. These impacts are presented as dose commitments to individuals and the regional population within an 80 km radius of the facility. Only airborne releases of radioactive materials are considered: releases to surface water and to groundwater are not addressed in MILDOS. This code is multi-purposed and can be used to evaluate population doses for NEPA assessments, maximum individual doses for predictive 40 CFR 190 compliance evaluations, or maximum offsite air concentrations for predictive evaluations of 10 CFR 20 compliance. Emissions of radioactive materials from fixed point source locations and from area sources are modeled using a sector-averaged Gaussian plume dispersion model, which utilizes user-provided wind frequency data. Mechanisms such as deposition of particulates, resuspension. radioactive decay and ingrowth of daughter radionuclides are included in the transport model. Annual average air concentrations are computed, from which subsequent impacts to humans through various pathways are computed. Ground surface concentrations are estimated from deposition buildup and ingrowth of radioactive daughters. The surface concentrations are modified by radioactive decay, weathering and other environmental processes. The MILDOS Computer Code allows the user to vary the emission sources as a step function of time by adjustinq the emission rates. which includes shutting them off completely. Thus the results of a computer run can be made to reflect changing processes throughout the facility's operational lifetime. The pathways considered for individual dose commitments and for population impacts are: • Inhalation • External exposure from ground concentrations • External exposure from cloud immersion • Ingestioo of vegetables • Ingestion of meat • Ingestion of milk • Dose commitments are calculated using dose conversion factors, which are ultimately based
Study of radiation detection properties of GaN pn diode
Sugiura, Mutsuhito; Kushimoto, Maki; Mitsunari, Tadashi; Yamashita, Kohei; Honda, Yoshio; Amano, Hiroshi; Inoue, Yoku; Mimura, Hidenori; Aoki, Toru; Nakano, Takayuki
2016-05-01
Recently, GaN, which has remarkable properties as a material for optical devices and high-power electron devices, has also attracted attention as a material for radiation detectors. We previously suggested the use of BGaN as a neutron detector material. However, the radiation detection characteristics of GaN itself are not yet adequately understood. For realizing a BGaN neutron detector, the understanding of the radiation detection characteristics of GaN, which is a base material of the neutron detector, is important. In this study, we evaluated the radiation detection characteristics of GaN. We performed I-V and energy spectrum measurements under alpha ray, gamma ray, and thermal neutron irradiations to characterize the radiation detection characteristics of a GaN diode. The obtained results indicate that GaN is an effective material for our proposed new BGaN-based neutron detector.
Effect of Ionizing Beta Radiation on the Mechanical Properties of Poly(ethylene under Thermal Stress
Directory of Open Access Journals (Sweden)
Bednarik Martin
2016-01-01
Full Text Available It was found in this study, that ionizing beta radiation has a positive effect on the mechanical properties of poly(ethylene. In recent years, there have been increasing requirements for quality and cost effectiveness of manufactured products in all areas of industrial production. These requirements are best met with the polymeric materials, which have many advantages in comparison to traditional materials. The main advantages of polymer materials are especially in their ease of processability, availability, and price of the raw materials. Radiation crosslinking is one of the ways to give the conventional plastics mechanical, thermal, and chemical properties of expensive and highly resistant construction polymers. Several types of ionizing radiation are used for crosslinking of polymers. Each of them has special characteristics. Electron beta and photon gamma radiation are used the most frequently. The great advantage is that the crosslinking occurs after the manufacturing process at normal temperature and pressure. The main purpose of this paper has been to determine the effect of ionizing beta radiation on the tensile modulus, strength and elongation of low and high density polyethylene (LDPE and HDPE. These properties were examined in dependence on the dosage of the ionizing beta radiation (non-irradiated samples and those irradiated by dosage 99 kGy were compared and on the test temperature. Radiation cross-linking of LDPE and HDPE results in increased tensile strength and modulus, and decreased of elongation. The measured results indicate that ionizing beta radiation treatment is effective tool for improvement of mechanical properties of LDPE and HDPE under thermal stress.
Ab-initio Calculation of Optoelectronic and Structural Properties of Cubic Lithium Oxide (Li2O)
Ziegler, Joshua; Polin, Daniel; Malozovsky, Yuriy; Bagayoko, Diola
Using the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF), we performed ab-initio, density functional theory (DFT) calculations of optoelectronic, transport, and bulk properties of Li2S. In so doing, we avoid ``band gap'' and problems plaguing many DET calculations [AIP Advances 4, 127104 (2014)]. We employed a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO). With the BZW-EF method, our results possess the full, physical content of DFT and agree with available, corresponding experimental ones. In particular, we found a room temperature indirect band gap of 6.659 eV that compares favorably with experimental values ranging from 5 to 7.99 eV. We also calculated total and partial density of states (DOS and PDOS), effective masses of charge carriers, the equilibrium lattice constant, and the bulk modulus. Acknowledgments: This work was funded in part by the National Science Foundation (NSF) and the Louisiana Board of Regents, through LASiGMA [Award Nos. EPS- 1003897, NSF (2010-15)-RII-SUBR] and NSF HRD-1002541, the US Department of Energy - National, Nuclear Security Administration (NNSA) (Award Nos. DE-NA0001861 and DE- NA0002630), LaSPACE, and LONI-SUBR.
Theoretical calculations on structural and electronic properties of BGaAsBi alloys
Aslan, Metin; Yalcin, Battal G.; Ustundag, Mehmet; Bagci, Sadik
2015-11-01
The structural and electronic properties of cubic B x Ga1- x As1- y Bi y alloys with bismuth (Bi) concentration of 0.0625, 0.125, 0.1875 and 0.25 are studied with various boron (B) compositions by means of density functional theory (DFT) within the Wu-Cohen (WC) exchange correlation potential based on generalized gradient approximation (GGA). For all studied alloy structures, we have implemented geometric optimization before the volume optimization calculations. The obtained equilibrium lattice constants and band gap of studied quaternary alloys are investigated for the first time in literature. While the lattice constant behavior changes linearly with boron concentration, increasing small amount of bismuth concentration alter the lattice constant nonlinearly. The present calculation shows that the band gap decreases with increasing bismuth concentration and direct band gap semiconductor alloy became an indirect band gap with increasing boron concentration. From the band offset calculation we have shown that increasing B and Bi concentration in host GaAs reduced the valance band offset in a heterostructure formed by GaAs and studied alloys.
Thermoelectric properties of AgSbTe₂ from first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Rezaei, Nafiseh; Akbarzadeh, Hadi [Department of Physics, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Hashemifar, S. Javad, E-mail: hashemifar@cc.iut.ac.ir [Department of Physics, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of)
2014-09-14
The structural, electronic, and transport properties of AgSbTe₂ are studied by using full-relativistic first-principles electronic structure calculation and semiclassical description of transport parameters. The results indicate that, within various exchange-correlation functionals, the cubic Fd3⁻m and trigonal R3⁻m structures of AgSbTe₂ are more stable than two other considered structures. The computed Seebeck coefficients at different values of the band gap and carrier concentration are accurately compared with the available experimental data to speculate a band gap of about 0.1–0.35 eV for AgSbTe₂ compound, in agreement with our calculated electronic structure within the hybrid HSE (Heyd-Scuseria-Ernzerhof) functional. By calculating the semiclassical Seebeck coefficient, electrical conductivity, and electronic part of thermal conductivity, we present the theoretical upper limit of the thermoelectric figure of merit of AgSbTe₂ as a function of temperature and carrier concentration.
Guo, San-Dong; Wang, Yue-Hua
2017-01-01
Two-dimensional (2D) materials may have potential applications in thermoelectric devices. In this work, the thermoelectric properties of orthorhombic group IV-VI monolayers AB (A = Ge and Sn; B = S and Se) are systematically investigated by the first-principles calculations and semiclassical Boltzmann transport theory. The spin-orbit coupling (SOC) is considered for their electron part, which produces observable effects on the power factor, especially for n-type doping. According to the calculated ZT, the four monolayers exhibit diverse anisotropic thermoelectric properties although they have a similar hinge-like crystal structure. The GeS along zigzag and armchair directions shows the strongest anisotropy, while SnS and SnSe show mostly isotropic efficiency of thermoelectric conversion. This can be explained by the strength of anisotropy of their respective power factor and electronic and lattice thermal conductivities. The calculated results show that the ZT between n- and p-type doping has little difference for GeS, SnS, and SnSe. It is found that GeSe, SnS, and SnSe show better thermoelectric performance compared to GeS in n-type doping and that SnS and SnSe exhibit higher efficiency of thermoelectric conversion in p-type doping. Compared to other many 2D materials, orthorhombic group IV-VI monolayers AB (A = Ge and Sn; B = S and Se) may possess better thermoelectric performance due to lower lattice thermal conductivities. Our work would be beneficial to stimulate further theoretical and experimental works.
Structural and electronic properties of cerium from LDA+U calculations
Directory of Open Access Journals (Sweden)
F. Kheradmand
2008-12-01
Full Text Available In this work structural, electronic and magnetic properties of alpha and gamma phases of cerium crystal have been calculated by means of the LDA and LDA+U methods. The equilibrium volume and magnetic moment obtained from the GGA approximation in agreement with the experiment are equal to 27.64 Å3 and 0.00018 µB, respectively. This agreement shows that the 4f electrons in alpha phase are itinerant due to the use of the GGA, where no strong correlations have been yet thaken into account. We have observed that even after applying the GGA+U method with U = 6.1 eV, the density of states of f orbital remains still at Fermi surface. Therefore, in complete accord with the experiment, our results show that the 4f electrons in the alpha phase are not localized. This is the case where the LDA and the GGA approximations could not describe the gamma phase properly. Indeed, physical properties of the gamma phase is consistent with the experiment and could only be reproduced after applying LDA+U method with U = 4.4 eV. In this way, the value of equilibrium volume and magnetic moment calculated for the gamma phase were found to be 34.33 Å3 and 1.15 µB, respectively. After including correlations among 4f electrons the γ-Ce DOS is positioned at its more reasonable place lower than Fermi level compared with the DOS obtained from GGA calculations. Our results, then, show that the 4f electrons in the gamma phase, as opposed to the alpha phase, are localized which is indicative of the fact that gamma cerium is a strongly correlated system. The volume of 11 kbar has been obtained for the pressure of the alpha-gamma phase transition .
Mehmood, Faisal; Pachter, Ruth; Murphy, Neil R.; Johnson, Walter E.
2015-11-01
Prediction of the frequency-dependent dielectric function of thin films poses computational challenges, and at the same time experimental characterization by spectroscopic ellipsometry remains difficult to interpret because of changes in stoichiometry and surface morphology, temperature, thickness of the film, or substrate. In this work, we report calculations for titanium nitride (TiN), a promising material for plasmonic applications because of less loss and other practical advantages compared to noble metals. We investigated structural, electronic, and optical properties of stoichiometric bulk TiN, as well as of the TiN(100), TiN(110), and TiN(111) outermost surfaces. Density functional theory (DFT) and many-body GW methods (Green's (G) function-based approximation with screened Coulomb interaction (W)) were used, ranging from G0W0, GW0 to partially self-consistent sc-GW0, as well as the GW-BSE (Bethe-Salpeter equation) and time-dependent DFT (TDDFT) methods for prediction of the optical properties. Structural parameters and the band structure for bulk TiN were shown to be consistent with previous work. Calculated dielectric functions, plasma frequencies, reflectivity, and the electron energy loss spectrum demonstrated consistency with experiment at the GW0-BSE level. Deviations from experimental data are expected due to varying experimental conditions. Comparison of our results to spectroscopic ellipsometry data for realistic nanostructures has shown that although TDDFT may provide a computationally feasible level of theory in evaluation of the dielectric function, application is subject to validation with GW-BSE calculations.
Properties and recrystallization of radiation damaged pyrochlore and titanite
Energy Technology Data Exchange (ETDEWEB)
Zietlow, Peter
2016-11-02
Radiation damage in minerals is caused by the alpha-decay of incorporated radionuclides, such as U and Th and their decay products. The effect of thermal annealing (400-1400 K) on radiation-damaged pyrochlores has been investigated by Raman scattering, X-ray powder diffraction (XRD), and combined differential scanning calorimetry/thermogravimetry (DSC/TG) (Zietlow et al., in print). The analysis of three natural radiation-damaged pyrochlore samples from Miass/Russia (6.4 wt% Th, 23.1.10{sup 18} a-decay events per gram (dpg)), Zlatoust/Russia (6.3 wt% Th, 23.1.10{sup 18} dpg), Panda Hill/Tanzania (1.6 wt% Th, 1.6.10{sup 18} dpg), and Blue River/Canada (10.5 wt% U, 115.4.10{sup 18} dpg), are compared with a crystalline reference pyrochlore from Schelingen (Germany). The type of structural recovery depends on the initial degree of radiation damage (Panda Hill 28 %, Blue River 85 %, Zlatoust and Miass 100 % according to XRD), as the recrystallization temperature increases with increasing degree of amorphization. Raman spectra indicate reordering on the local scale during annealing-induced recrystallization. As Raman modes around 800 cm{sup -1} are sensitive to radiation damage (Vandenborre and Husson 1983, Moll et al. 2011), the degree of local order was deduced from the ratio of the integrated intensities of the sum of the Raman bands between 605 and 680 cm{sup -1} devided by the sum of the integrated intensities of the bands between 810 and 860 cm{sup -1}. The most radiation damaged pyrochlores (Miass and Zlatoust) show an abrupt recovery of both, its short- (Raman) and long-range order (X-ray) between 800 and 850 K. The volume decrease upon recrystallization in Zlatoust pyrochlore was large enough to crack the sample repeatedly. In contrast, the weakly damaged pyrochlore (Panda Hill) begins to recover at considerably lower temperatures (near 500 K), extending over a temperature range of ca. 300 K, up to 800 K (Raman). The pyrochlore from Blue River shows in its
Effect of UV/EB radiation dosages on the properties of nanocomposite coatings
Energy Technology Data Exchange (ETDEWEB)
Nik Salleh, Nik Ghazali, E-mail: Nik_Ghazali@nuclearmalaysia.gov.m [Malaysian Nuclear Agency, Block 42, Radiation Curing and Synthesis Group, Bangi, 43000 Kajang, Selangor (Malaysia); Firdaus Yhaya, Mohd; Hassan, Azman; Abu Bakar, Aznizam; Mokhtar, Munirah [Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)
2011-02-15
The aim of this study was to compare the effects of ultraviolet (UV) and electron beam (EB) radiation on the properties of cured nanocomposite coatings. Surface hardness increased with increase in radiation dosages (number of passes) for all samples. This was due to the increase in crosslinking with increase in radiation dosage. Pendulum hardness, gel content, and thumb twist results were analyzed to choose appropriate curing dosage for both curing techniques. The selected dosages were then used to cure coatings for scratch and abrasion resistance tests. It was found that the UV curing produced coatings with better abrasion resistance, whereas EB curing was a more suitable approach for producing scratch resistance coatings.
Saurabh, Chaturbhuj K; Gupta, Sumit; Bahadur, Jitendra; Mazumder, S; Variyar, Prasad S; Sharma, Arun
2013-11-06
Mechanical and water vapor barrier properties of biodegradable films prepared from radiation processed guar gum were investigated. Films prepared from GG irradiated up to 500 Gy demonstrated significantly higher tensile strength as compared to non-irradiated control films. This improvement in tensile strength observed was demonstrated to be due to the ordering of polymer structures as confirmed by small angle X-ray scattering analysis. Exposure to doses higher than 500 Gy, however, resulted in a dose dependent decrease in tensile strength. A dose dependent decrease in puncture strength with no significant differences in the percent elongation was also observed at all the doses studied. Water vapor barrier properties of films improved up to 15% due to radiation processing. Radiation processing at lower doses for improving mechanical and barrier properties of guar based packaging films is demonstrated here for the first time. Copyright © 2013 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Martin-Rengel, M.A. [Departamento de Ciencia de Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, Profesor Aranguren s/n, E-28040 Madrid (Spain); Consejo de Seguridad Nuclear (CSN), Justo Dorado 11, E-28040 Madrid (Spain); Gomez, F.J.; Ruiz-Hervias, J.; Caballero, L.; Valiente, A. [Departamento de Ciencia de Materiales, UPM, E.T.S.I. Caminos, Canales y Puertos, Profesor Aranguren s/n, E-28040 Madrid (Spain)
2009-06-15
Nuclear fuel cladding is the first barrier used to confine the fuel and the fission products produced during irradiation. Zirconium alloys are used for this purpose due to their remarkable neutron transparency, together with their good mechanical properties at operational temperatures. Consequently, it is very important to be able to characterize the mechanical response of the irradiated cladding. The mechanical behaviour of the material can be modelled as elastoplastic with different stress-strain curves depending on the direction: radial, hoop or longitudinal direction. The ring tensile test has been proposed to determine the mechanical properties of the cladding along the hoop direction. The initial test consisted of applying a force inside the tube, by means of two half cylinders. Later Arsene and Bai [1,2] modified the experimental device to avoid tube bending at the beginning of the test. The same authors proposed a numerical method to obtain the stress-strain curve in the hoop direction from the experimental load versus displacement results and a given friction coefficient between the loading pieces and the sample [3]. This method has been used by different authors [4] with slight modifications. It is based on the existence of two universal curves under small strain hypothesis: the first correlating the hoop strain and the displacement of the loading piece and the second one correlating the hoop stress and the applied load. In this work, a new method to determine the mechanical properties of the cladding from the ring tensile test results is proposed. Non-linear geometry is considered and an iterative procedure is proposed so universal curves are not needed. A stress-strain curve is determined by combining numerical calculations with experimental results in a convergent loop. The two universal curves proposed by Arsene and Bai [3] are substituted by two relationships, one between the equivalent plastic strain in the centre of the specimen ligament and the
Luminescence properties of porcelain ceramics relevant to restrospective radiation dosimetry
DEFF Research Database (Denmark)
Bøtter-Jensen, L.; Markey, B.G.; Poolton, N.R.J.
1996-01-01
. This appears to arise from the fact that OSL is potentially stimulated in a variety of component phases of the ceramic, and these phases vary from sample to sample. This article reports an initial attempt at characterising the luminescence properties of widely available porcelain wares manufactured under...
Tracking properties of the ATLAS Transition Radiation Tracker (TRT)
Krasnopevtsev, Dimitriy; The ATLAS collaboration
2016-01-01
The tracking performance parameters of the ATLAS Transition Radiation Tracker (TRT) as part of the ATLAS Inner Detector are described for different data taking conditions in proton-proton, proton-lead and heavy ion collisions at the Large Hadron Collider (LHC). These studies are performed using data collected during the first and the second periods of LHC operation and are compared with Monte Carlo simulations. The performance of the TRT, operating with different gas mixtures (Xenon-based and Argon-based) and for high track multiplicities is presented. These studies show that the tracking performance of the TRT with these two gas mixtures is similar and that the detector still provides a significant contribution to the particle momentum measurement of the overall Inner Detector of the ATLAS experiment.
Ab initio quantum Monte Carlo calculations of ground-state properties of manganese's oxides
Sharma, Vinit; Krogel, Jaron T.; Kent, P. R. C.; Reboredo, Fernando A.
One of the critical scientific challenges of contemporary research is to obtain an accurate theoretical description of the electronic properties of strongly correlated systems such as transition metal oxides and rare-earth compounds, since state-of-art ab-initio methods based on approximate density functionals are not always sufficiently accurate. Quantum Monte Carlo (QMC) methods, which use statistical sampling to evaluate many-body wave functions, have the potential to answer this challenge. Owing to the few fundamental approximations made and the direct treatment of electron correlation, QMC methods are among the most accurate electronic structure methods available to date. We assess the accuracy of the diffusion Monte Carlo method in the case of rocksalt manganese oxide (MnO). We study the electronic properties of this strongly-correlated oxide, which has been identified as a suitable candidate for many applications ranging from catalysts to electronic devices. ``This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.'' Ab initio quantum Monte Carlo calculations of ground-state properties of manganese's oxides.
Khadraoui, Z.; Horchani-Naifer, K.; Ferhi, M.; Ferid, M.
2015-09-01
Single crystals of TbPO4 were grown by high temperature solid-state reaction and identified by means of X-ray diffraction, infrared and Raman spectroscopies analysis. The electronic properties of TbPO4 such as the energy band structures, density of states were carried out using density functional theory (DFT). We have employed the LDA+U functional to treat the exchange correlation potential by solving Kohn-Sham equation. The calculated total and partial density of states indicate that the top of valance band is mainly built upon O-2p states and the bottom of the conduction band mostly originates from Tb-5d states. The population analysis indicates that the P-O bond was mainly covalent and Tb-O bond was mainly ionic. The emission spectrum, color coordinates and decay curve were employed to reveal the luminescence properties of TbPO4. Moreover, the optical properties including the dielectric function, absorption spectrum, refractive index, extinction coefficient, reflectivity and energy-loss spectrum are investigated and analyzed. The results are discussed and compared with the available experimental data.
Ansari, Reza; Ajori, Shahram; Malakpour, Sina
2016-04-01
The considerable demand for novel materials with specific properties has motivated the researchers to synthesize supramolecular nanostructures through different methods. Porous graphene is the first two-dimensional hydrocarbon synthesized quite recently. This investigation is aimed at studying the mechanical properties of atom-decorated (functionalized) porous graphene by employing density functional theory (DFT) calculation within both local density approximations (LDA) and generalized gradient approximations (GGA). The atoms are selected from period 3 of periodic table as well as Li and O atom from period 2. The results reveal that metallic atoms and noble gases are adsorbed physically on porous graphene and nonmetallic ones form chemical bonds with carbon atom in porous graphene structure. Also, it is shown that, in general, atom decoration reduces the values of mechanical properties such as Young's, bulk and shear moduli as well as Poisson's ratio, and this reduction is more considerable in the case of nonmetallic atoms (chemical adsorption), especially oxygen atoms, as compared to metallic atoms and noble gases (physical adsorption).
Han, Kuk-Il; Kim, Do-Hwi; Choi, Jun-Hyuk; Kim, Tae-Kuk; Shin, Jong-Jin
2016-09-01
Infrared signals are widely used to discriminate objects against the background. Prediction of infrared signal from an object surface is essential in evaluating the detectability of the object. Appropriate and easy method of procurement of the radiative properties such as the surface emissivity, bidirectional reflectivity is important in estimating infrared signals. Direct measurement can be a good choice but a costly and time consuming way of obtaining the radiative properties for surfaces coated with many different newly developed paints. Especially measurement of the bidirectional reflectivity usually expressed by the bidirectional reflectance distribution function (BRDF) is the most costly job. In this paper we are presenting an inverse estimation method of the radiative properties by using the directional radiances from the surface of concern. The inverse estimation method used in this study is the statistical repulsive particle swarm optimization (RPSO) algorithm which uses the randomly picked directional radiance data emitted and reflected from the surface. In this paper, we test the proposed inverse method by considering the radiation from a steel plate surface coated with different paints at a clear sunny day condition. For convenience, the directional radiance data from the steel plate within a spectral band of concern are obtained from the simulation using the commercial software, RadthermIR, instead of the field measurement. A widely used BRDF model called as the Sandford-Robertson(S-R) model is considered and the RPSO process is then used to find the best fitted model parameters for the S-R model. The results obtained from this study show an excellent agreement with the reference property data used for the simulation for directional radiances. The proposed process can be a useful way of obtaining the radiative properties from field measured directional radiance data for surfaces coated with or without various kinds of paints of unknown radiative
Safronova, U I; Johnson, W R
2016-01-01
Energy levels of 30 low-lying states of Lu2+ and allowed electric-dipole matrix elements between these states are evaluated using a relativistic all-order method in which all single, double and partial triple excitations of Dirac-Fock wave functions are included to all orders of perturbation theory. Matrix elements are critically evaluated for their accuracy and recommended values of the matrix elements are given together with uncertainty estimates. Line strengths, transition rates and lifetimes of the metastable 5d(3/2) and 5d(5/2) states are calculated. Recommended values are given for static polarizabilities of the 6s, 5d and 6p states and tensor polarizabilities of the 5d and 6p(3/2) states. Uncertainties of the polarizability values are estimated in all cases. The blackbody radiation shift of the 6s(1/2)-5d(5/2) transition frequency of the Lu2+ ion is calculated with the aid of the recommended scalar polarizabilities of the 6s(1/2) and 5d(5/2) states. Finally, A and B hyperfine constants are determined f...
Goriely, S; Krewald, S
2011-01-01
The E1 strength function for 15 stable and unstable Sn even-even isotopes from A=100 till A=176 are calculated using the self-consistent microscopic theory which, in addition to the standard (Q)RPA approach, takes into account the single-particle continuum and the phonon coupling. Our analysis shows two distinct regions for which the integral characteristics of both the giant and pygmy resonances behave rather differently. For neutron-rich nuclei, starting from $^{132}$Sn, we obtain a giant E1 resonance which significantly deviates from the widely-used systematics extrapolated from experimental data in the $\\beta$-stability valley. We show that the inclusion of the phonon coupling is necessary for a proper description of the low-energy pygmy resonances and the corresponding transition densities for $A132$ region the influence of phonon coupling is significantly smaller. The radiative neutron capture cross sections leading to the stable $^{124}$Sn and unstable $^{132}$Sn and $^{150}$Sn nuclei are calculated wi...
Safronova, U. I.; Safronova, M. S.; Johnson, W. R.
2016-09-01
Energy levels of 30 low-lying states of Lu2 + and allowed electric-dipole matrix elements between these states are evaluated using a relativistic all-order method in which all single, double, and partial triple excitations of Dirac-Fock wave functions are included to all orders of perturbation theory. Matrix elements are critically evaluated for their accuracy and recommended values of the matrix elements are given together with uncertainty estimates. Line strengths, transition rates, and lifetimes of the metastable 5 d3 /2 and 5 d5 /2 states are calculated. Recommended values are given for static polarizabilities of the 6 s , 5 d , and 6 p states and tensor polarizabilities of the 5 d and 6 p3 /2 states. Uncertainties of the polarizability values are estimated in all cases. The blackbody radiation shift of the 6 s1 /2-5 d5 /2 transition frequency of the Lu2 + ion is calculated with the aid of the recommended scalar polarizabilities of the 6 s1 /2 and 5 d5 /2 states. Finally, A and B hyperfine constants are determined for states of 2+175Lu with n ≤9 . This work provides recommended values of transition matrix elements, polarizabilities, and hyperfine constants of Lu2 +, critically evaluated for accuracy, for benchmark tests of high-precision theoretical methodology and planning of future experiments.
Energy Technology Data Exchange (ETDEWEB)
Han, Gi Young; Seo, Bo Kyun [Korea Institute of Nuclear Safety,, Daejeon (Korea, Republic of); Kim, Do Hyun; Shin, Chang Ho; Kim, Song Hyun [Dept. of Nuclear Engineering, Hanyang University, Seoul (Korea, Republic of); Sun, Gwang Min [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2016-06-15
In analyzing residual radiation, researchers generally use a two-step Monte Carlo (MC) simulation. The first step (MC1) simulates neutron transport, and the second step (MC2) transports the decay photons emitted from the activated materials. In this process, the stochastic uncertainty estimated by the MC2 appears only as a final result, but it is underestimated because the stochastic error generated in MC1 cannot be directly included in MC2. Hence, estimating the true stochastic uncertainty requires quantifying the propagation degree of the stochastic error in MC1. The brute force technique is a straightforward method to estimate the true uncertainty. However, it is a costly method to obtain reliable results. Another method, called the adjoint-based method, can reduce the computational time needed to evaluate the true uncertainty; however, there are limitations. To address those limitations, we propose a new strategy to estimate uncertainty propagation without any additional calculations in two-step MC simulations. To verify the proposed method, we applied it to activation benchmark problems and compared the results with those of previous methods. The results show that the proposed method increases the applicability and user-friendliness preserving accuracy in quantifying uncertainty propagation. We expect that the proposed strategy will contribute to efficient and accurate two-step MC calculations.