Radiation transport model

Solar Radiation in the Atmosphere Solar radiation is modified considerably on its path from the top of the atmosphere down to the sea surface. The simple radiation transport model used here follows mainly Bodin (1979), modified by Meier et al. (1999). The radiation at the sea surface is described as... 

The models proposed to represent radiation transport process can be grouped into two classes. The first and simpler approach is to use some form of the Stefan-Boltzmann equation for radiant exchange between opaque gray bodies,... 

By far, the most widely used model in calculating hemodynamic response is based on the classic Beer-Lambert law. The Beer-Lambert law is derived from solution to radiation transport equation under several simplifying assumptions [91]. It describes a linear relationship between absorbance, A, of light through a medium and wavelength dependent extinction coefficient, e(A). This relationship is given by Equation (1)... 

Recently there has been interest in the sorptive behavior of natural clays toward metal ions potentially present in radioactive wastes. Initial studies of the transplutonium elements have been carried out to define their sorption behavior with such materials ( ). However, it is also important to understand the stability of the clay-actinide product with regard to radiation damage and to be able to predict what changes in behavior may occur after exposure to radiation, so that accurate transport models may be constructed. 

Model calculations performed during PAUR I included three-dimensional regional Chemistry-Transport Models to study chemical processes and transport at the regional and the urban level and radiation transfer models. These models were applied for a number of ozone depletion scenaria. 

In connection with the SHEBA project, the U.S. Department of Energy s Atmosphere Radiation Measurement (ARM) program indicated its intention to develop a Cloud and Radiation Testbed (CART) facility on the North Slope of Alaska. The principal focus of this program will be on atmospheric radiative transport, especially as modified by clouds (such transport impacts the growth and decay of sea ice), as well as testing, validation, and comparison of radiation transfer models in both the ice pack and Arctic coastal environment. 

In the current state-of-the-art, one-dimensional models can best be used to look in detail at the coupling of a very large number of species interactions in a geometry that is an approximation to reality. Processes such as radiation transport, turbulence, or the effects of heterogeneity of materials can be included either as empirically or theoretically derived submodels. 

In enclosure fires, radiation may be the dominant mode of heat transfer. For flames burning in an open atmosphere, the radiative fraction of overall heat transfer ranges from less than 0.1 to 0.4, depending both on the fuel type and the fire diameter [45], Owing to the important role that radiation plays in fires, all fire CFD models have a radiation model that solves the radiation transport equation (RTE) [46,48] ... 

The experimental results were analyzed using an integrated approach. To obtain the temporal evolution of the temperature and the density profiles of the bulk plasma, the experimental hot-electron temperature was used as an initial condition for the 1D-FP code [26]. The number of hot electrons in the distribution function were adjusted according to the assumed laser absorption. The FP code is coupled to the 1-D radiation hydrodynamic simulation ILESTA [27]. The electron (or ion) heating rate from hot electrons is first calculated by the Fokker-Planck transport model and is then added to the energy equation for the electrons (or ions) in ILESTA-1D. Results were then used to drive an atomic kinetics package [28] to obtain the temporal evolution of the Ka lines from partially ionized Cl ions. 

The radiation-hydrodynamic simulation includes the Quotidien EOS [29] and Ion EOS based on the Cowan model [30], For the electron component, a set of fitting formulae derived from the numerical results from the Thomas-Fermi model and a semi-empirical bonding correction [31] are adopted. The effective Z-number of the partially ionized plasma is obtained from the average atom model. Radiation transport is treated by multigroup diffusion. 

Owens, A. J., C. H. Hales, D. L. Filkin, C. Miller, J. M. Steed, and J. P. Jesson (1985). A coupled one-dimensional radiation-convective chemistry transport model of the atmosphere. 1. Model structure and steady-state perturbation calculations. J. Geophys. Res. 90, 2283-2311. 

The TRIO-VF computer code was improved in order to calculate transport of sodium aerosols in gas volume. The generation phenomena and physics of sodium aerosols have been modelized as well as coupling between free convection, radiation transport and aerosols transport. 

EPRI (Electric Power Research Institute) Proceedings of the BWR Radiation Control and Radwaste Processing Seminar. Report EPRI NP-2417-LD (1982) Chapter 16 Hemmi, Y, Kamata, T., Nakayama, Y, Tani, A., Morikawa, Y, Sato, Y, Nagao, H., Sasaki, S., Sato, Y, Kuba, M., Kakefuda, M. BWR cobalt transport model. Proc. 2. BNES Conf Water Chemistry of Nuclear Reactor Systems, Bournemouth, UK, 1980, p. 319-326... 

In general, organ doses carmot be measured directly they have to be calculated by radiation transport simulations, mostly using Monte Carlo techniques and computational models of the human body. The results of these calculations are so-called organ dose conversion coefficients, i.e., mean organ doses normalized to a measurable dose quantity, such as the CTDl (see below). 

The latest development is now to combine continuous photochemistry with microstmctured equipment. Only very recenfly photochemical conversions in microreactors have received a considerable amount of attention due to the problem often encountered in conventional photoreactors that the distribution of radiation is inhomogeneous in the reaction zone. During the scale-up process, such inhomogeneities often require intensive modeling and design considerations usually on the basis of photon transport models [66], and such models have been, for example, developed for biomedical and analytical purposes [67]. The problem of the intensity distribution in a reactor is illustrated in Figure 3.10. It is obvious that spatial restriction of the irradiation zone in a microphotoreactor to a... 

Nonetheless, these methods only estimate organ-averaged radiation dose. Any process which results in high concentrations of radioactivity in organs outside the MIRD tables or in very small volumes within an organ can result in significant error. In addition, the kinetic behavior of materials in the body can have a dramatic effect on radiation dose and models of material transport are constandy refined. Thus radiation dosimetry remains an area of significant research activity. 

GASFLOW models geometrically complex containments, buildings, and ventilation systems with multiple compartments and internal structures. It calculates gas and aerosol behavior of low-speed buoyancy driven flows, diffusion-dominated flows, and turbulent flows dunng deflagrations. It models condensation in the bulk fluid regions heat transfer to wall and internal stmetures by convection, radiation, and condensation chemical kinetics of combustion of hydrogen or hydrocarbon.s fluid turbulence and the transport, deposition, and entrainment of discrete particles. 

Atmospheric aerosols have a direct impact on earth s radiation balance, fog formation and cloud physics, and visibility degradation as well as human health effect[l]. Both natural and anthropogenic sources contribute to the formation of ambient aerosol, which are composed mostly of sulfates, nitrates and ammoniums in either pure or mixed forms[2]. These inorganic salt aerosols are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence in humid air. That is, relative humidity(RH) history and chemical composition determine whether atmospheric aerosols are liquid or solid. Aerosol physical state affects climate and environmental phenomena such as radiative transfer, visibility, and heterogeneous chemistry. Here we present a mathematical model that considers the relative humidity history and chemical composition dependence of deliquescence and efflorescence for describing the dynamic and transport behavior of ambient aerosols[3]. 

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