Energy Distribution Of Radiation Research Articles

Numerical investigation of oxy-coal combustion in a large-scale furnace: Non-gray effect of gas and role of particle radiation

Computational fluid dynamics (CFD) simulations of the oxy-coal combustion in a large-scale furnace were performed by applying different weighted sum of gray-gases models (WSGGMs). Before simulation of the furnace, the different WSGGMs were tested in an enclosed rectangular box containing only gases inside. In both cases of air and oxy-fuel combustion, the calculated radiative sources and wall heat fluxes obtained with gray and non-gray WSGGMs were completely different. Only with the non-gray WSGGMs (i.e., non-gray implementation), the calculated results could well agree with the benchmark data. In the simulation of furnace, three WSGGMs were adopted: Smith’s gray WSGGM (i.e., gray implementation), Johansson’s non-gray-A WSGGM with uniform distribution of radiative energy of particles in each gray band, and Johansson’s non-gray-B WSGGM, in which the radiative energy of particles was distributed using weighting factors. The weighting factors for the particles can be calculated with the same function as that used for gas but using the particle temperature instead of gas temperature, i.e., wp,i=wg,i (Tp). Being different from the rectangular box without particle radiation, in the real furnace, the gas temperature and wall heat flux calculated by gray and non-gray-A WSGGMs almost show no obvious difference. This is attributed to the fact that particle radiation plays a more significant role than gas radiation in the real furnace. However, using the non-gray-B model instead of Smith’s gray model or non-gray-A model can obviously influence the distribution of wall heat flux and total amount of heat absorbed by the walls. This indicates that in the numerical simulation of oxy-fuel combustion, the non-gray WSGGMs should be used by combining with the weighting factors of wp,i=wg,i (Tp) for particles, in order to rigorously describe both the gas and particle radiation during oxy-fuel combustion of coal in real furnace.

Black hole mass dynamics and renormalization group evolution

We examine the real-time dynamics of a system of one or more black holes interacting with long wavelength gravitational fields. We find that the (classical) renormalizability of the effective field theory that describes this system necessitates the introduction of a time dependent mass counterterm, and consequently the mass parameter must be promoted to a dynamical degree of freedom. To track the time evolution of this dynamical mass, we compute the expectation value of the energy-momentum tensor within the in-in formalism, and fix the time dependence by imposing energy-momentum conservation. Mass renormalization induces logarithmic ultraviolet divergences at quadratic order in the gravitational coupling, leading to a new time-dependent renormalization group (RG) equation for the mass parameter. We solve this RG equation and use the result to predict heretofore unknown high order logarithms in the energy distribution of gravitational radiation emitted from the system.

Microdosimetric characterisation of radiation fields for modelling tissue response in radiotherapy

Purpose: Our overall goal is the development of an approach to model tissue response to radiotherapy in which a tissue is viewed as a statistical ensemble of interacting cells. This involves characterisation of radiation fields on the spatial scale of subcellular structures. On this scale, the spatial distribution of radiation energy imparted to tissue is highly non-uniform and should be characterised in statistical terms. Microdosimetry provides a formalism developed for that purpose. This study addresses limitations of the standard microdosimetric approach to modelling tissue response by introducing two new characteristics that include additional information in a form convenient for this application. Methods : The standard microdosimetric approach is based on the concept of a sensitive volume (SV) representing a target volume in the cell. It is considered in isolation from other SVs, implying that energy depositions in different SVs are statistically independent and that individual cells respond to radiation independent of each other. In this study, we examined the latter approximation through analysis of correlation functions. All calculations were performed with Geant4-DNA Monte Carlo code. Results: We found that for some realistic scenarios, spatial correlations of deposited energy can be significant. Two new characteristics of radiation fields are proposed. The first is the specific energy-volume histogram (zVH), which is a microscopic analogue of the dose-volume histogram. The second describes the probability distribution of deposited energies in two SVs without assuming statistical independence between the SVs. Numerical examples for protons and carbon ions of therapeutic energies are presented and discussed. Conclusion: We extended the microdosimetric approach to modelling tissue response by including additional important characteristics and presented them in a more conventional radiotherapy format. --------------------------------------------- Cite this article as : Wang H, Vassiliev ON. Microdosimetric characterisation of radiation fields for modelling tissue response in radiotherapy. Int J Cancer Ther Oncol 2014; 2 (1):020116. DOI : http://dx.doi.org/10.14319/ijcto.0201.16

Numerical modelling the unsteady process of closed rectangular area radiant heating in conjugate formulation with accounting energy distribution along horizontal and vertical enclosure structures

Mathematical modelling of unsteady convective-conductive heat exchange in premises, heated by infrared radiant heater is passed. Heat flux density from infrared radiant heater was calculated accounting energy distribution along horizontal and vertical building envelope. Comparison between zonal method and Lambert's law radiant energy distribution was done.

A Multi-Modal Analysis of Climate-Economics

We investigate the qualitative properties of the climate-economic growth model introduced by Brock et al., (2012). We assume that the mean annual distribution of solar radiation energy and the fraction of incoming radiation flux absorbed by the surface have a specific form, and perform a rigorous mathematical analysis when the time scale for temperature is taken to be faster than that of carbon. We analyze the impact of moving welfare weights away from Negishi weights by introducing a simple welfare weights function. We perform a qualitative analysis on the output elasticities of carbon and capital, and examine the way thermal diffusion affects local economic variables and taxes at the equilibrium. We then evaluate the robustness of the two- and four-mode forms in the context of the temperature model.

Calculation of spatial distribution of energy of a complex radiator

The paper presents the results of calculating spatial distribution of radiant energy from a radiator consisting of a cylindrical source of radiation and two disk reflectors, accordingly, with a diffuse character of radiation and reflection. A program of modeling optical parameters of complex reflectors is used as the basic tool of calculation. The basis for the procedure applied is the iterative-zonal method the essence of which consists in separating the radiating and reflecting systems as well as the light-trapping hemisphere into mentary platforms. The exchange of energy between the platforms is defined by means of a forward stroke beam method. The results of calculation are compared to the experimental data obtained in the course of the model light experiment.

Probability characteristics of thermal infrared radiation for anisotropic spheres

针对红外探测制导和检测等研究的热点问题, 探讨了目标红外辐射的方向性对红外探测的影响.以各向异性等温球体为研究对象, 建立从目标到探测器敏感面阵的红外传输整体模型.以能量概率密度分布函数为基础, 构造敏感面上单元格的能量描述方法.采用蒙特卡洛法, 计算单元格的红外信号强度, 分析红外小目标的方向辐射特性对探测敏感面上能量分布的影响.结果表明, 当目标表面半球方向发射率一定时, 提高法向发射率可显著增强目标中心所在像元的红外信号强度, 增大目标像元间红外信号对比度.;In accordance with the hot issues of infrared detection and guidance, an IR transmission process from target to sensitive array was established to explore the IR signatures of an anisotropic-isothermal sphere model. The energy probability density distribution function was employed to describe the energy intensity levels of sensitive array units. The energy distributions of detector units were abtained with the aid of the Monte Carlo Method. The relationship between target directional IR radiation characteristics and energy distributions on the sensitive array was revealed. It indicates that in the case of the equal hemispherical emissivity of far-field small targets, increasing the emissivity in the near-normal direction can appreciably enhance the IR intensity of the image-center unit and improve the IR intensity contrast among the image units.

Numerical simulations of the solar transmission process for a pressurized volumetric receiver

A three-dimensional optical model for a pressurized volumetric receiver (PVR) is developed and corresponding solar radiation propagation process within the PVR is simulated by the Monte Carlo Ray Tracing (MCRT) method. In the computation, the complicated photon transmission process in the SiC porous absorber is simplified as the transmission process in the statistically homogeneous and isotropic turbid medium. Meanwhile, the non-uniform cylindrical coordinate grid is applied in the statistics of energy distribution, which could greatly reduce the number of cells in the computational grid and time compared with normal uniform grid. Based on the above model, the energy distribution in the irregular macro scale porous absorber is determined and then the effects of system parameters, including the incidence angle, the shape of absorber and the optical property of absorber, on the local heat flux of the absorber are investigated. The results show that, under the given operating condition, the radiation heat flux is mostly concentrated at the top area of the absorber and the maximum heat flux value is up to 2.73 × 109 W m−3, but it quickly decreases in the sideward locations. The incidence angle and a relative narrow shape of absorber are helpful to reduce the maximum heat flux in the absorber. Furthermore, as the ratio of absorption coefficient/extinction coefficient decreases, the absorbed radiation energy distribution is more uniform and the max heat flux in the absorber decreases greatly.

What the exercise of the SPICE source inversion validation BlindTest 1 did not tell you

Uncertainties of earthquake finite-fault inversions based upon strong motion data are investigated using the source inversion validation BlindTest 1 exercise of the SPICE (Seismic Wave Propagation and Imaging in Complex Media: A European Network) project, motivated by previous counterintuitive results. The distribution of slip and the shapes of asymmetric slip rate functions are simultaneously inverted by matching 10 or 33 broad-band three-component velocity waveforms within the period ranging from 0.02 to 2 Hz, using a finite-fault method that carries out the waveform inversion in the wavelet domain. The effects of subfault size, data noise and the number of stations have been explored. Our results suggest: (1) Although there are inevitable discrepancies between the inverted model and the target model because of ignoring the spatial slip variations within individual subfaults, the fault slip and rise-time distributions can be well constrained even with the data including large Gaussian noise. (2) It is crucial for source studies to develop new inversion schemes that can properly honour the frequency- and time-dependent energy distribution of seismic radiation and data noise. For instance, inversions using the variance reduction function of velocity waveforms as the objective function have low sensitivities to the total seismic moment and peak slip. (3) Although the relative value of the objective function is guided in the inversion, the absolute value of the objective function cannot be used to evaluate the quality of an inverted model. (4) Because the source inversion is based on surface observations, the spatiotemporal resolution of source inversion is affected not only by the data quality but also by the earthquake itself. For vertical strike-slip faults, the along-strike resolution is better than that along the downdip direction.

Modeling the spatial distribution of the radiant energy density and absorbed dose of radiation in the DNA structure under accelerated heavy ions

Model approaches are developed to the description of the mechanism of the formation of different types of atomic-level DNA lesions under accelerated heavy ions. The radial distribution of radiant energy and the absorbed dose are calculated in accelerated 4He, 12C, and 40Ar ion tracks in the energy range of 3–20 MeV/nucleon. The spatial location of the atoms of an adenine-thymine nucleotide pair is compared with the calculated radial dose and radiant energy density distributions.

Clouds in the atmospheres of extrasolar planets

We study the influence of low-level water and high-level ice clouds on low-resolution reflection spectra and planetary albedos of Earth-like planets orbiting different types of stars in both the visible and near infrared wavelength range. We use a one-dimensional radiative-convective steady-state atmospheric model coupled with a parametric cloud model, based on observations in the Earth's atmosphere to study the effect of both cloud types on the reflection spectra and albedos of Earth-like extrasolar planets at low resolution for various types of central stars. We find that the high scattering efficiency of clouds substantially causes both the amount of reflected light and the related depths of the absorption bands to be substantially larger than in comparison to the respective clear sky conditions. Low-level clouds have a stronger impact on the spectra than the high-level clouds because of their much larger scattering optical depth. The detectability of molecular features in near the UV - near IR wavelength range is strongly enhanced by the presence of clouds. However, the detectability of various chemical species in low-resolution reflection spectra depends strongly on the spectral energy distribution of the incident stellar radiation. In contrast to the reflection spectra the spectral planetary albedos enable molecular features to be detected without a direct influence of the spectral energy distribution of the stellar radiation. Here, clouds increase the contrast between the radiation fluxes of the planets and the respective central star by about one order of magnitude, but the resulting contrast values are still too low to be observable with the current generation of telescopes.

Polarization of AGN in UV spectral range

We present the review of some new problems in cosmology and physics of stars in connection with future launching of WSO. We discuss three problems. UV observations of distant z > 6 quasars allow to obtain information on the soft < 1 KeV X-ray radiation of the accretion disk around a supermassive black hole because of its cosmological redshift. Really the region of X-ray radiation is insufficiently investigated because of high galactic absorption. In a result one will get important information on the reionization zone of the Universe. Astronomers from ESO revealed the effect of alignment of electric vectors of polarized QSOs. One of the probable mechanism of such alignment is the conversion of QSO radiation into low mass pseudoscalar particles (axions) in the extragalactic magnetic field. These boson like particles have been predicted by new SUSY particle physics theory. Since the probability of such conversion is increasing namely in UV spectral range one can expect the strong correlation between UV spectral energy distribution of QSO radiation and polarimetric data in the optical range. In the stellar physics one of the interesting problems is the origin of the X-ray sources with super Eddington luminosities. The results of UV observations of these X-ray sources will allow to find the origin of these sources as accreting intermediate mass black holes.

The Characteristics of Atmospheric Turbulence and Radiation Energy Transfer and the Structure of Atmospheric Boundary Layer over the Northern Slope Area of Himalaya

The mountains of Himalayas are the important channels for the mass exchange between surface layer of Northern Hemisphere and troposphere. The mountains relate surface layer atmosphere over the Tibetan Plateau and the above free atmosphere through many atmospheric circulation systems including mountain-valley wind and glacier wind etc. Mt. Qomolangma (Mt. Everest) is the highest peak in the world, and its nearby region is a representative case of mountains of Himalayas. Firstly the back ground of the establishment of the Qomolangma Station for Atmospheric and Environmental Observation and Research, Chinese Academy of Sciences (QOMS/ CAS) and the role of the station in the study of the atmosphere-land interaction over Himalayan area were intro-duced in this paper. Then some preliminary observational analysis results, such as the structure of the Atmo-spheric Boundary Layer (ABL) and the characteristics of the atmospheric turbulence and the radiation energy distribution were shown. The results showed that: The excess resistance to heat transfer kB-1 has obvious diurnal variations with lower values in the night and higher values in the daytime; The low frequency perturbations have a large influence on the spectra variation of all wind components, but mid frequency perturbations have only in-fluence on the spectra variation of vertical wind components and also alter the co-spectra of momentum and sen-sible heat flux under near neutral stratification; The downward shortwave radiation over this area are obviously larger than that in other areas; There is very clear constant layer of potential temperature existing in the northern slope of Mt. Qomolangma area around 12:00 (Beijing Standard Time, BST) in May, and the layer is about 2,200 m during the period over this area. In comparison with study results from other areas, some uniqueness and commonness of the Himalayan region are clearly identified.

A three‐dimensional characterization of Arctic aerosols from airborne Sun photometer observations: PAM‐ARCMIP, April 2009

The Arctic climate is modulated, in part, by atmospheric aerosols that affect the distribution of radiant energy passing through the atmosphere. Aerosols affect the surface‐atmosphere radiation balance directly through interactions with solar and terrestrial radiation and indirectly through interactions with cloud particles. Better quantification of the radiative forcing by different types of aerosol is needed to improve predictions of future climate. During April 2009, the airborne campaign Pan‐Arctic Measurements and Arctic Regional Climate Model Inter‐comparison Project (PAM‐ARCMIP) was conducted. The mission was organized by Alfred Wegener Institute for Polar and Marine Research of Germany and utilized their research aircraft, Polar‐5. The goal was to obtain a snapshot of surface and atmospheric conditions over the central Arctic prior to the onset of the melt season. Characterizing aerosols was one objective of the campaign. Standard Sun photometric procedures were adopted to quantify aerosol optical depth AOD, providing a three‐dimensional view of the aerosol, which was primarily haze from anthropogenic sources. Independent, in situ measurements of particle size distribution and light extinction, derived from airborne lidar, are used to corroborate inferences made using the AOD results. During April 2009, from the European to the Alaskan Arctic, from sub‐Arctic latitudes to near the pole, the atmosphere was variably hazy with total column AOD at 500 nm ranging from ∼0.12 to &gt;0.35, values that are anomalously high compared with previous years. The haze, transported primarily from Eurasian industrial regions, was concentrated within and just above the surface‐based temperature inversion layer. Extinction, as measured using an onboard lidar system, was also greatest at low levels, where particles tended to be slightly larger than at upper levels. Black carbon (BC) (soot) was observed at all levels sampled, but at moderate to low concentrations compared with historical records. BC was highest near the North Pole, suggesting there had been an accumulation of soot within the Arctic vortex. Few, optically thick elevated aerosol layers were observed along the flight track, although independent lidar observations reveal evidence of the passage of volcanic plumes, which may have contributed to abnormally high values of AOD above 4 km. Enhanced opacity at higher altitudes during the campaign is attributed to an accumulation of industrial pollutants in the upper troposphere in combination with volcanic aerosol resulting from the March–April 2009 eruptions of Mount Redoubt in Alaska. The presence of Arctic haze during April 2009 is estimated to have reduced the net shortwave irradiance by ∼2–5 W m−2, resulting in a slight cooling of the surface.

Radiation from a charged particle-in-flight from a laminated medium to vacuum

The radiation from a charged particle-in-flight from a semi-infinite laminated medium to vacuum and back,- from vacuum to the laminated medium, has been investigated. Expressions for the spectral-angular distribution of radiation energy in vacuum (at large distances from the boundary of laminated medium) were obtained for both the cases with no limitations on the amplitude and variation profile of the laminated medium permittivity. The results of appropriate numerical calculations are presented and possible applications of the obtained results are discussed.

SU‐GG‐J‐53: A Novel Dose Reconstruction Method for Four‐Dimensional Treatment Planning

Purpose: To present a novel dose mapping algorithm that takes into account heterogeneity effects of radiation energy distribution in 4D planning, and compare it with two well‐established dose calculation strategies. Method and Materials: A 4DCT dataset was imported into Eclipse and the end‐inhalation image (EI) was used to develop a free‐breathing lung cancer radiotherapy treatment plan. The EI was registered to the end‐exhalation image (EE, reference) using a B‐Spline deformable registration algorithm. The resultant displacement map Φ, defined from EE to EI, was iteratively reversed to generate a self‐inverse consistent map ΦR. With the Eclipse Advanced Planning‐Interface (API, Varian Medical Systems), the mass density matrix of EI was derived from the treatment plan and mapped to EE using ΦR. The dose was calculated on the EI using the AAA algorithm and multiplied by the mass density matrix of EI to generate the deposited energy. The energy was then mapped to the image EE again using ΦR. The warped dose D on the EE image was calculated as the ratio of the mapped energy and mass (REM). For comparison, two additional approaches were used that warped the dose on EI with Φ: center of mass (COM) and trilinear dose interpolation (TRI). The three dose reconstruction strategies were then compared on the reference image (EE). Results: The average spatial difference between the composition of Φ and ΦR and the identity map was approximately 0.0 mm. On average, the dose to 95% of the ITV (D95) was 70.2%, 67.5%, and 64.3% for the REM, TRI, and COM methods, respectively. The dose difference between COM and REM was up to 14.5% at the high gradient beam edges. Conclusion: The independent mappings of mass and energy may help minimize heterogeneity‐induced dose interpolation errors, thereby improving dose mapping accuracy in 4D treatment planning.

Radiation model of a TiO2‐coated, quartz wool, packed‐bed photocatalytic reactor

AbstractThe radiation field of a packed‐bed photocatalytic reactor filled with quartz wool coated with titanium dioxide was modeled using the Monte Carlo technique and the following information: the radiation flux emitted by the lamps, the diameter size distribution of the quartz fiber cloth, the mass of quartz fibers and of TiO2 that was immobilized on the fiber surface as well as the refractive index, and the spectral absorption coefficient of the materials of the system. Modeling predictions were validated with radiometer measurements of the transmitted radiation through the reactor, the root mean square error being &lt;9.7%. Finally, by means of a parametric study, the validated model was used to analyze the effect of the design variables, such as the radii of the quartz fibers, thickness of the TiO2 coatings, and amount of TiO2‐coated quartz wool, on the distribution and nonuniformity of the radiative energy distribution inside the reactor. © 2009 American Institute of Chemical Engineers AIChE J, 2010

Radiant energy distribution in guava (Psidium guajava L.) plants at different spacings

The study on radiant energy distribution in guava was carried out to optimize the planting density with respect to solar radiation interception by the plants to get higher yield of good quality fruits per unit area. The present investigations reveals that with increase in plant spacing from 6x2m to 6x4m the interception of radiation increased significantly during both rainy and winter crop seasons. However, it starts declining with further increase in plant spacing to 6x5m level. The interception of radiation remains somewhat static during the summer and rainy season months (May-September) and then starts decreasing with the advent of winter season upto April with sharp decline during the month of December to February. In the upper 1/3rd portion of plant canopy, more than 75% radiations were intercepted irrespective of plant spacing followed by 12-16% in middle and 6-9% in the lower 1/3rd parts of plant canopies. The plant spacing of 6x2m and 6x3m was found to be not encouraging owing to lower distribution of radiations particularly in middle and lower parts of plants. The plant spacing of 6x4m was found to be best due tomaximum absorption of solar radiation for higher fruiting of better quality fruits.

Modeling of optical radiation energy distribution in plant tissue

A three-dimensional mathematical model of interactions of optical radiation with plant tissue taking into account its structural inhomogeneity, spectral properties, and the effects of fluorescence is constructed. The developed model is implemented using the statistical Monte Carlo method for the Henyey-Greenstein phase function. The dependence of differential backscattering and fluorescence coefficients on the concentration of photosynthetic pigments (chlorophylls) is numerically studied. It is demonstrated that numerical characteristics agree with results of physical experiment. The approximate solution based on the expansion of the diffusion and fluorescence radiation fluxes into a series in terms of a small parameter is found. This expansion makes it possible to calculate the field of backscattered radiation with satisfactory accuracy and to qualitatively correctly describe the experimentally observed dependences of the fluorescence coefficient in the region of high chlorophyll concentration.

Continuous spectrum generated by the excited dental X-ray tube

The continuous X-ray spectral profiles have been successfully produced using the excited dental X-ray tube, where used dental X-ray tube was employed in the experimental setup. The effect of parameters on the continuous spectrum is investigated, whereas the major parameters are the anode current and adjustable voltage. It was found that the optimum conditions for the threshold voltage were three times higher than the highest energy absorption edge with tungsten anode target on the spectral distribution of radiation energy, which was increased, and the short wavelengths limitation obtained are 1.03, 0.73, 0.59, 0.48 and 0.46 Å.. The relative sensitivity is increased from 12 to 25 kV, and it is decreased at 26 and 27 kV. The intensity near the short wavelength is increased by the double voltage value.