Distribution Of Radiation Research Articles

Novel additive-manufactured tracking solar concentrating system for cooking applications: Design, geometry assessment, and optical evaluation

A novel solar concentrating system for cooking applications was developed, featuring a stationary reflector and a flat heliostat with equatorial tracking. This design allows for simple one-axis tracking at a constant speed with no need for deformable reflectors, ensuring the direction of the concentrated radiation in the cooking area remains steady and a quasi-constant power capture regardless of the Sun's position. The concentrator is made from 3D printed flat tiles, allowing for an easy do-it-yourself manufacturing process and avoiding highly focused irradiance on the receiver. The geometry of the reflector was scanned and compared to an ideal CAD reflector model, revealing some assembly imperfections, and a slightly concave tile geometry which causes a moderately sharp concentration peak. The irradiance distribution on a plane target near the effective focus of the reflector was analysed with a photographic flux mapping technique, and the results were compared to those obtained from ray tracing simulations of the ideal CAD model, confirming the tile concavity predicted by the geometrical examination. Conversely, it shows a reduction in the total energy gathered on the entire target plate when compared with ray tracing outcomes.

Polymer Boron-Containing Composite for Protecting Astronauts of Manned Orbital Stations from Secondary Neutron Radiation

This article considers the prospects of using heat-resistant polyimide boron-containing composites to protect astronauts of manned orbital stations from secondary neutron radiation. Variant calculations are performed regarding neutron and gamma-quanta flux distributions in a polyimide composite material with different boron content used to reduce capture radiation. The dependences of spatial distributions of thermal neutron flux density and the gamma-quanta dose rate in a polyimide composite layer with a boron content of 0 to 5% are obtained. An experimental assessment of the energy distribution of neutron and gamma radiation behind the protective polyimide composite is carried out. The introduction of boron atoms in an amount of 3.0 wt.% shows the absence of bursts of secondary gamma radiation energy in the composite, which is due to the high cross-section of thermal neutron absorption by boron atoms. As a result, with a material layer thickness of 3–10 cm, the gamma-quanta dose rate decreases by 2–3 times. The differential thermal analysis method showed that the upper limit of the working temperature of the polyimide composite is 500 °C. The polyimide matrix filled with boron atoms can find effective application in the development of new radiation-protective polymer materials used in manned orbital stations.

Vertical structures of typhoon cloud microphysical and radiative features associated with the precipitation type over the western North Pacific

Intensity of different precipitation types (convective, stratiform and shallow) and associated cloud vertical microphysical and radiative heating features are analyzed considering typhoon development, maturity, and decaying stages over the western North Pacific using the CloudSat Tropical Cyclone and China Meteorological Administration tropical cyclone best-track datasets from 2 June 2006 to 31 December 2015. At all three stages, the convective precipitation intensity, approximately twice that of stratiform precipitation, is the highest and peaks at development stage. The strongest stratiform precipitation occurs at typhoon maturity stage. Shallow precipitation is the weakest throughout the typhoon lifespan. Although the cloud microphysical parameters (radar reflectivity, cloud ice particle number concentration and effective radius) of both convective and stratiform precipitation tend to increase with precipitation intensity, convective precipitation contains more ice water of larger sizes in upper layers than stratiform precipitation. Unlike convective and stratiform precipitation, dominated by cold clouds, shallow precipitation is dominated by warm clouds with weak vertical contrast in the radiative distribution but strong radiation nearby 5 km. Our results show that cloud ice particle number concentration is important not only in precipitation intensity enhancement but also in determining the shortwave radiative heating center vertical location. More and larger ice particles in convective precipitation profiles result in stronger or comparable shortwave radiative heating than those in stratiform precipitation profiles, while the longwave radiative cooling rates in convective and stratiform precipitation profiles exhibit very similar features, likely attributable to similar infrared radiation levels due to comparable temperatures in these profiles.

Optical beam spread in seawater

We study the spatial and angular distribution of light in a narrow stationary beam propagating in a medium like seawater. For a power-law parametrization of the seawater phase function, using radiative transfer analysis, we derive analytical expressions that determine the radiance distribution in the medium. Both the case of intermediate source–receiver distances, where absorption only begins to affect spreading of the beam, and the asymptotic regime of beam propagation are examined. For the main characteristics of the radiance distribution (the total power, the variance of the angular and radial distributions), scaling relations involving the inherent optical parameters of seawater are found. To validate the expressions obtained we carry out Monte Carlo simulation for commonly adopted seawater scattering models (of Petzold and Morel et al) and their analytical parameterizations. For optical parameters typical to seawater, the predicted analytical laws are in excellent agreement with the results of the Monte Carlo computations.

An efficient 3D tube-level flux-thermal model of external tubular receivers in solar power tower systems

Accurate and efficient radiative flux simulation and thermal analysis of liquid tubular receivers are essential for safe and stable operations of solar power tower systems. However, the complicated structure and photothermal processes on these receivers pose significant challenges for simulation. Although existing models have made great simplifications, the simulation results are still inefficient and inaccurate. To address these issues, a novel and universal 3D flux-thermal model is proposed. Firstly, a flux model is proposed via a tube-level Monte Carlo ray tracing method based on GPU parallel computing, enabling real-time and accurate radiative flux density distribution simulation for each absorber tube. Secondly, a high-resolution multi-tube thermal model is proposed, providing accurate 3D thermal analysis for each absorber tube. Through pre-factorization and highly parallelized designs, the proposed thermal model achieves a 600 times acceleration in efficiency, even with tens of millions of discrete elements. Finally, the novel flux-thermal model is validated against publicly published measured data from Solar Two, indicating a mean deviation of only 0.1% and a root mean square error of 0.006, demonstrating its high accuracy. Furthermore, the proposed flux-thermal model reveals complex and asymmetrical flux and temperature distributions on the absorber tube, in contrast to the symmetrical distributions obtained by the simplified models. Such inaccuracies in the simplified simulations may cause operational misjudgements and affect system safety potentially. Therefore, the proposed 3D tube-level flux-thermal model provides an accurate and efficient solution to radiative flux simulation and thermal analysis, enhancing the safe and stable operation of solar power tower systems.

Entropy generated nonlinear mixed convective beyond constant characteristics nanomaterial wedge flow

Background and objectiveNanomaterial flows at present have received much attention of the researchers. Such motivation stems for their utilization in pharmaceutical, industrial, petroleum, manufacturing and engineering applications including regenerative medicine, treatment of cancer, electronic device cooling, solar collector, mineral oil, antimicrobial agents, thermal storage system, transformer cooling and X-imaging etc. Higher thermal energy requirement in several electrical and mechanical systems is desired in recent time due to high advancement of science and technology. For important application here the stagnation point flow due to wedge with nonlinear convection is explored. For porous media, the Darcy-Forchheimer relation is considered. Characteristics of nanofluid is added by utilizing Buongiorno's model. Variable fluid characteristics are under consideration. Applied magnetic field is accounted. Energy expression comprises thermal radiation, Brownian motion, Ohmic heating, thermophoresis and heat generation. First order reaction and entropy rate are considered. MethodologyNonlinear differential expressions are changed into dimensionless ordinary systems through adequate transformations. The resultant nonlinear ordinary systems are solved through optimal homotopy analysis technique (OHAM). ResultsOutcomes for influential variables about temperature, velocity, concentration and entropy rate have been arranged. Here results show that for magnetic field the liquid flow and entropy rate have opposite scenarios. Thermal distribution and concentration have reverse effects for random motion variable while similar effect holds for thermophoresis parameter. Magnetic field and diffusion parameters contribute to augment entropy generation. Higher values of temperature dependent electrical conductivity variable lead to increase entropy rate. Thermal distribution for radiation and Eckert number is similar.

Зависимость величины сигнала от смещения функции рассеяния точки, вписанной в четыре пиксела матрицы

An algorithm has been developed for calculating changes in the signal level of a matrix pixel when the point scattering function is shifted at an angle of 45º relative to the joining point of 4 matrix pixels. In the initial state of the point spread function, the point is inscribed in four pixels. The spectral sensitivity of a pixel is constant within the pixel area. The distribution of pixel irradiance in the point spread function in the form of uniform irradiance is considered. Method. The calculation is based on the method of dividing the point spread function on each pixel of the matrix into separate areas for which the signal is calculated. The displacement of the point scattering function by Δx along the X axis and by Δy along the Y axis is taken in a form normalized to the radius of the spot. To create a two-dimensional graph of the dependence of the pixel signal on the displacement of the point scattering function along the X, Y axes, we introduce the relative displacement of the point scattering function η. Main results. An algorithm has been developed for calculating changes in the signal level of a matrix pixel when the point scattering function is shifted relative to the matrix pixels for the case of pixel irradiation in the lens scattering circle in the form of uniform irradiance. The dependence of the normalized matrix pixel signal on the relative displacement of the point scattering function η at an angle of 45º has been plotted for the above case of irradiation. Practical significance. Matrix photodetectors are widely used in guidance and tracking systems for space objects and astronomical sensors. For a defocused optical system, uniform distribution is used. When the point scattering function shifts relative to the joining point of the four pixels of the matrix, the matrix signal drops, which, with a low signal-to-noise ratio, can lead to a breakdown in tracking or an increase in the error in measuring the angular coordinates of a space object. The results of these studies can be used to model a target guidance system and determine target coordinates.

Coulomb excitation of hydrogen atoms by vortex ion beams

Abstract Coulomb excitation of hydrogen atoms by vortex protons is theoretically investigated within the framework of the non--relativistic first--Born approximation and the density matrix approach. Special attention is paid to the magnetic sublevel population of excited atoms and, consequently, to the angular distribution of the fluorescence radiation. We argue that both these properties are sensitive to the projection of the orbital angular momentum (OAM), carried by the projectile ions. In order to illustrate the OAM--effect, detailed calculations have been performed for the $1s \to 2p$ excitation and the subsequent $2p \to 1s$ radiative decay of a hydrogen target, interacting with incident Laguerre--Gaussian vortex protons. The calculation results suggest that Coulomb excitation can be employed for the diagnostics of vortex ion beam at accelerator and storage ring facilities.

Design and modeling of PV-integrated Double Skin Facades and application to retrofit buildings

Double Skin Façade (DSF) system comprises two glazing layers with a ventilated cavity. Integrating photovoltaic (PV) modules within the outer layer of DSFs offers an efficient method for electricity generation. Current tools for modeling and analyzing DSF systems are complex and resource-intensive, lacking the capability to evaluate the performance of innovative PV-DSF systems during the early design stage. This study develops a mathematical model to evaluate the electrical and thermal performance of PV-DSF systems, considering architectural design elements such as PV color and relative orientation. Based on an energy balance approach, the model is particularly suited for designing PV-DSF systems in heritage buildings, which often have color and relative orientation constraints. The model is applied to assess the performance of PV-DSF systems with conventional clear glass PV and colored front glass PV modules under the climatic conditions of Montreal, Canada. Results indicated that conventional clear glass PV module exhibit higher PV cell temperature than colored PV modules due to greater transmissivity, with peak temperature differences at noon of 5.5 °C, 6.2 °C, and 6.5 °C for orange, blue, and gray PV modules, respectively. On the contrary, the influence of PV's color front glass on room air temperature is non-significant. Furthermore, the optimal orientation for maximum energy yield is not always south-facing; it depends on the hourly distribution of the beam, diffuse solar irradiation, and ambient air temperature. For Montreal, west-facing DSFs produce more electrical and thermal energy on a summer design day because the hourly distribution of beam radiation is skewed towards afternoon hours.

Study of the Spatial Distribution of X-Pinch Plasma Radiation Using a New-Type Coded Aperture

To study the spatial distribution of the intensity of an X-ray source of electric discharge plasma, a new-type coded aperture, which is a structure of intersecting mutually perpendicular transparent and opaque strips with the widths selected using a random number generator, has been used. The radiation passed through the coded aperture has produced a complex pattern of the coded image, which has been recorded on a Fuji TR fluorescent imaging plate without a protective coating. A mathematical procedure based on the iterative method of solving an incorrectly posed problem given by the Fredholm integral equation of the first kind has been applied to reconstruct the spatial distribution of plasma radiation intensity from this pattern. It has been shown that the use of the coded aperture not only has increased significantly the light intensity of the recording system in comparison with a pinhole camera, but also has made it possible to obtain a spatial resolution of the discharge plasma no worse than the resolution of the pinhole camera. The applicability of the developed iterative method for both sources close to point ones and extended emitting objects has been demonstrated.

Optical characterization and thermal performance of a novel solar dryer with dynamic control of solar radiation

In this study, a novel adaptive solar dryer with a coating of polymer-dispersed liquid crystals (PDLC) was designed, built, and characterized to evaluate its optical properties and thermal performance by modulating the transmission of solar radiation toward the drying chamber. PDLC films can electrically switch between opaque and transparent states, making them ideal for controlling solar radiation. Unlike conventional direct dryers, the proposed solar drying system takes advantage of direct solar radiation, known for its rapid drying process, while minimizing the impact on product properties. The results show that the PDLC coating exhibited a significant difference in transmittance between the “on” and “off” states under ambient conditions. At 400 nm, the transmittance varied by 20 %, increasing to 30 % at 450 nm. The solar dryer with dynamic control of solar irradiance constantly maintained a temperature range of 52.19 °C–57 °C. Lower relative humidity values were achieved compared to the uncontrolled solar dryer, resulting in a uniform irradiance distribution within the drying cabinet. The solar dryer with dynamic control of solar irradiance (acrylic and PDLC film) presents a total thermal resistance (0.02817 mK/W) exhibiting better heat permanence inside the drying cabinet compared to polycarbonate (one of the materials most used for drying systems). The system's thermal efficiency ensures reliable operation regardless of weather conditions, efficiently capturing and converting solar energy into heat.

Optimization of Lamps Configuration for a Large-scale Indoor Solar Simulator for PV Panels and Solar Collectors

The current study presents investigations of a solar simulator design, development, and performance characterization for the application of photovoltaic (PV), thermal collector, and photovoltaic/thermal (PV/T) indoor experiments. The study highlights the research outcomes of the lamp configurations and numbers in the simulator to achieve an acceptable radiation distribution in the targeted area as per the ASTM standards. Tungsten Halogen lamps were used to mimic solar radiation due to their proximity to the solar spectrum of the visible and infrared band and relatively low cost. The results indicate that a solar simulator of Class-C for spatial uniformity and Class-A for temporal uniformity can be achieved with the application of Tungsten Halogen lamps if arranged properly and a range of radiation flux can be obtained to replicate the variation of solar flux during the daytime. It was observed that three to six lamps of 1kW arranged in specific configurations can provide solar radiation varying from 378 to 969 W/m2 mimicking the daytime solar flux variation on an experimental area of 1200 × 520 mm2.

Statistical Analysis of Annual DNI Distribution and its Impact on Bankability Assessment for Concentrated Solar Power Plants

The Weibull distribution is commonly accepted as the most suitable model for describing the annual distribution of Direct Normal Irradiance (DNI). However, when the annual DNI is assumed to follow a Normal distribution instead of a Weibull distribution, there is a notable increase in the cumulative annual values for unfavourable and worst-case scenarios. In this research, we assess the suitability of different statistical indexes for goodness-of-fit by applying them to the annual cumulative DNI and Global Horizontal Irradiance (GHI) data recorded at six locations with varying climates. Our observations reveal that, across all locations, the Representative Solar Year (RSY) aligns with the 50% Probability of Exceedance (PoE50) of a Normal distribution fitted to the observed data. We quantify that assuming the annual DNI conforms to a Weibull distribution, as opposed to a Normal distribution, results in a substantial decrease of approximately 7% in the annual cumulative value for the worst-case scenario. Based on our analysis, we find no compelling evidence to reject the hypothesis that the annual DNI follows a Normal distribution.

The exact relativistic scalar quasibound states of the dyonic Kerr–Sen black hole: quantized energy, and Hawking radiation

We consider Klein–Gordon equation in the Dyonic Kerr–Sen black hole background, which is the charged rotating axially symmetric solution of the Einstein–Maxwell–Dilaton–Axion theory of gravity. The black hole incorporates electric, magnetic, dilatonic and axionic charges and is constructed in 3+1 dimensional spacetime. We begin our investigations with the construction of the scalar field’s governing equation, i.e., the covariant Klein–Gordon equation. With the help of the ansatz of separation of variables, we successfully separate the polar part, and find the exact solution in terms of Spheroidal Harmonics, while the radial exact solution is obtained in terms of the Confluent Heun function. The quantization of the quasibound state is done by applying the polynomial condition of the Confluent Heun function that gives rise to discrete complex-valued energy levels for massive scalar fields. The real part is the scalar field relativistic quantized energy, while the imaginary part represents the quasibound states’s decay. We present all of the sixteen possible exact energy solutions for both massive and massless scalars. We also present the investigation the Hawking radiation of the Dyonic Kerr–Sen black hole’s apparent horizon, via the Sigurd–Sannan method by making use of the obtained exact scalar wave functions. The radiation distribution function, and the Hawking temperature are also obtained.

Inverse problem for thermal radiation distribution on turbine blade under quartz lamp irradiation

Due to the strong time-varying characteristics and complex geometry of aerospace components, rapid changes in the distribution of radiative heat flux on the test surface are often required during non-uniform aerodynamic heating tests. However, it takes time to adjust the geometric parameters of the lamp array, which cannot meet the requirement for rapidly changing radiative heat flux distribution. To address this issue, a new method for calculating radiant heat flux and a fast linear analysis method of quartz lamp power are proposed which can calculate radiant heat flux distribution of complex surface and meet the need of timeliness and rapidity in radiant heat flux distribution, making it more suitable for engineering applications. Through numerical verification under single lamp and quartz lamp array, the maximum difference between the theoretical analysis method and the Monte Carlo method is less than 2.25% under single lamp, and less than 5% under quartz lamp array. Finally, turbine blade model and plane model are taken as research objects to verify the feasibility and reliability of the fast linear analysis method of quartz lamp power. The results show that the relative average error of the calculated quartz lamp power is 5.86% and 14.83%, respectively, compared with the actual power. This provides a reference and basis for the rapid simulation design of thermal radiation environment during the experiment.

Evaluation of radiation leakage in X-ray security inspection machine using a CZT spectrometer

Leakage radiation from X-ray security inspection machines is important, and measurement based on ionization chamber or scintillator detector is widely used. The leakage radiation is closely related to the size and the passing time of the luggage, the lead equivalent, the opening angle of the lead curtain, and the response time of the measuring instrument. To characterize the distribution of leakage radiation from the X-ray security inspection machine accurately, a small-volume CZT(CdZnTe) spectrometer was used to measure the energy spectra at a distance of 5 cm from the surface of the inspection machine. By designing and controlling the opening angle of the lead curtain according to the size of the luggage passing through the entrance and exit, the radiation dose was determined based on the measured energy spectra combined with the G(E)-function method. The results show that the maximum relative deviation between the air kerma rate and the ambient dose equivalent rate calculated by the G(E) function method with the standard dose rate does not exceed ±5%. The maximum relative deviation of the dose rate linear verification in the 137Cs radiation field is less than 2.5%. A calibrated CZT detector was utilized to measure the radiation leakage on the surface of the X-ray security inspection machine. It was discovered that the presence of the luggage items and the opening angle of the lead curtain will increase the leakage radiation dose on the surface of the security inspection machine system. This study provides a new approach for measuring scattered radiation of X-ray security inspection machines.

Tracing the physical signatures among the calculated global clear-sky spectral shortwave radiative flux distribution

This study utilized the high-spectral resolution radiative transfer model (MODerate resolution atmospheric TRANsmission, MODTRAN6.0.2.5) to compute global clear-sky shortwave (SW) radiative flux and compared it with NASA’s Clouds and the Earth’s Radiant Energy System (CERES) Synoptic Radiative Fluxes and Clouds (SYN1deg) product. The comparison revealed that the global distributions of clear-sky downwelling SW fluxes at the surface from the M6.0 calculations and SYN1 results are similar, with annual means of 246.51 Wm-2 and 242.42 Wm-2, respectively. Analysis further showed that most of the M6.0 calculations are slightly higher from low to mid-latitudes, particularly in the Northern Hemisphere (NH), but lower in higher latitudes compared to SYN1 results. However, these differences mostly fall within the CERES estimated uncertainty (6 Wm-2) of monthly mean clear-sky downwelling SW flux at the surface. The sensitivity of clear-sky SW/μ0 fluxes to changes in Precipitable Water Vapor (PWV), represented by the clear-sky water vapor radiative kernel, is about -0.7 Wm-2/(kgm-2) over oceans for both M6.0 and CERES SYN1 products, except for SYN1 results over the Southern Hemisphere (SH) ocean. Additionally, the zonal means of land coverage and SW/VIS/NIR albedos from M6.0 calculations indicate that VIS albedos are highest in polar regions (>60°), followed by SW and NIR albedos, while NIR albedos become highest from low to mid-latitudes (<60°). Generally, SW/VIS/NIR albedos and their differences increase monotonically with increased land coverage from 60°S to 60°N. The consistent clear-sky water vapor radiative kernels derived from both products exceeded our expectations, suggesting their potential use to trace physical signatures in climate model calculations. It is recommended that these model-derived radiative kernels should be validated by the long-term global and regional surface observations in order to enhance confidence to implement these radiative kernels in climate models.

Experimental study on the effect of light source arrangements on the disinfection performance of upper-room 222 nm Far-UVC

The air disinfection efficacy of upper-room 222 nm Far-UVC was experimentally investigated in a real-size chamber under well-mixed air conditions. Two bacteria (Escherichia coli, Staphylococcus epidermidis) and two bacteriophages (MS2, and P22) were selected for the test. The study considered different lamp source arrangements, including single and double sources, stationary and rotating operating modes, and an overlapping mode with a 45° irradiation angle. A numerical view-factor model was developed to analyze the irradiance distributions. Four irradiation angles, 30°, 45°, 60°, and 90°, were chosen. The results show that the lamps operating with an irradiation angle of 45° provide the highest chamber-averaged irradiance. This suggests an optimal irradiance level for a given room dimension, as inferred from the view factor model. Experimental results indicated that the overlapping mode with a 45° irradiation angle consistently outperformed both the stationary mode and rotating mode in disinfection. This can be attributed to the higher chamber-averaged irradiance, which is also supported by the numerical model predictions. The increment ratios ranged from 14.9 % to 42.9 % compared to the stationary mode. The susceptibility constants of Escherichia coli, Staphylococcus epidermidis, MS2, and P22 were measured as 0.572 m2/J, 0.099 m2/J, 0.060 m2/J, and 0.081 m2/J respectively.

Evaluation of radiation protection effectivity in a cardiac angiography room using visualized scattered radiation distribution

In this study, we devised a radiation protection tool specifically designed for healthcare professionals and students engaged in cardiac catheterization to easily monitor and evaluate scattered radiation distribution across diverse C-arm angles and arbitrary physician associated staff positions—scrub nurse and technologist positions. In this study, scattered radiation distributions in an angiography room were calculated using the Monte Carlo simulation of particle and heavy ion transport code system (PHITS) code. Four visualizations were performed under different C-arm angles with and without radiation protection: (1) a dose profile, (2) a 2D cross-section, (3) a 3D scattered radiation distribution, and (4) a 4D scattered radiation distribution. The simulation results detailing the scattered radiation distribution in PHITS were exported in Visualization Toolkit format and visualized through the open-source visualization application ParaView for analysis. Visualization of the scattered dose showed that dose distribution depends on the C-arm angle and the x-ray machine output parameters (kV, mAs s−1, beam filtration) which depend upon beam angulation to the patient body. When irradiating in the posterior–anterior direction, the protective curtain decreased the dose by 62% at a point 80 cm from the floor, where the physician’s gonads are positioned. Placing the protection board close to the x-ray tube reduced the dose by 24% at a location 160 cm from the floor, where the lens of the eye is situated. Notably, positioning the protection board adjacent to the physician resulted in a 95.4% reduction in incident air kerma. These visualization displays can be combined to understand the spread and direction of the scattered radiation distribution and to determine where and how to operate and place radiation protection devices, accounting for the different beam angulations encountered in interventional cases. This study showed that scatter visualization could be a radiation protection teaching aid for students and medical staff in angiography rooms.

Sun Declination and Distribution of Natural Beam Irradiance on Earth

Sun Declination and Distribution of Natural Beam Irradiance on Earth