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We investigate the Dirac and Klein-Gordon equations, as well as greybody radiation, for the Hayward black hole (BH) space-time. We first consider the Dirac equation using a null tetrad in the Newman-Penrose formalism. The equations are then separated into angular and radial parts. A pair of one-dimensional Schrodinger-like wave equations with effective potentials is obtained from the radial part. In order to examine the behavior of potentials, they are plotted with respect to radial distances. Additionally, the Klein-Gordon equation is considered in the Hayward BH space-time. At the end, we compute greybody factors for bosons and fermions and our results are shown graphically and discussed. Key words: Hayward black hole, Dirac equation, Klein-Gorden equations, greybody factors, radiation, 1. Introduction Regular black holes (BHs) were discovered first by Bardeen and came to be known as Bardeen BHs [1-3]. These types of BHs do have an event horizon but [...]

Byline: Siti. Zuber, Muhammad. Abdul Hadi, Damilola. Samson, Jayapramila. Jayamani, Nor. Rabaiee, Mohd. Abdul Aziz, Nurul. Aziz Hashikin, Chee. Ying, Mohd. Mohd Yusof, Rokiah. Hashim Purpose: This study aims to [...]

The problem of sound radiation from a train is considered. This object has been simulated as sets of point sources uniformly distributed in the domain of a moving lengthened rectangle. The solution of the problem is obtained using integral Fourier transforms over the space coordinates and time. The integrals are calculated by using the stationary phase method. Numerical analysis is carried out for acoustic pres-sure and sound intensity., UDC 539.3:534.242 1. Formulation and Analysis Fast trains are sources of significant noise. In the last years, the problem of sound generation by trains and the protection of the natural [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.06.002 Byline: Jose A. Ruiz-Arias (a), TomaA Cebecauer (b)(c)(d), Joaquin Tovar-Pescador (a), Marcel A uri (b)(c) Keywords: Solar irradiance; Satellite; Digital elevation model; DEM; Disaggregation Abstract: Downscaling of the Meteosat-derived solar radiation ([approximately equal to]5km grid resolution) is based on decomposing the global irradiance and correcting the systematic bias of its components using the elevation and horizon shadowing that are derived from the SRTM-3 digital elevation model (3 arc sec resolution). The procedure first applies the elevation correction based on the difference between coarse and high spatial resolution. Global irradiance is split into direct, diffuse circumsolar and diffuse isotropic components using statistical models, and then corrections due to terrain shading and sky-view fraction are applied. The effect of reflected irradiance is analysed only in the theoretical section. The method was applied in the eastern Andalusia, Spain, and the validation was carried out for 22days on April, July and December 2006 comparing 15-min estimates of the satellite-derived solar irradiance and observations from nine ground stations. Overall, the corrections of the satellite estimates in the studied region strongly reduced the mean bias of the estimates for clear and cloudy days from roughly 2.3% to 0.4%. Author Affiliation: (a) Department of Physics, University of Jaen, Spain (b) European Commission, Joint Research Centre, Ispra, Italy (c) GeoModel s.r.o., Bratislava, Slovakia (d) Institute of Geography, Slovak Academy of Sciences, Bratislava, Slovakia Article History: Received 10 February 2009; Revised 20 April 2010; Accepted 6 June 2010 Article Note: (miscellaneous) Communicated by: Associate Editor David Renne

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.06.006 Byline: Claudia Valeria Tavora Cabral (a), Delly Oliveira Filho (a), AntA[acute accent]nia SA[acute accent]nia Alves C. Diniz (b), Jose Helvecio Martins (a), Olga Moraes Toledo (a), Lauro de Vilhena B. Machado Neto (b) Keywords: Deterministic sizing; Stochastic sizing; Solar energy; Stand-alone photovoltaic systems; Probabilistic modeling Abstract: Photovoltaic systems utilize solar energy to generate electrical energy to meet load demands. Optimal sizing of these systems includes the characterization of solar radiation. Solar radiation at the Earth's surface has random characteristics and has been the focus of various academic studies. The objective of this study was to stochastically analyze parameters involved in the sizing of photovoltaic generators and develop a methodology for sizing of stand-alone photovoltaic systems. Energy storage for isolated systems and solar radiation were analyzed stochastically due to their random behavior. For the development of the methodology proposed stochastic analysis were studied including the Markov chain and beta probability density function. The obtained results were compared with those for sizing of stand-alone using from the Sandia method (deterministic), in which the stochastic model presented more reliable values. Both models present advantages and disadvantages, however, the stochastic one is more complex and provides more reliable and realistic results. Author Affiliation: (a) Department of Agricultural Engineering, Federal University of Vicosa, Av. P. H. Rolfs, s/n. 36570-000 Vicosa, Minas Gerais, Brazil (b) Group of Studies in Energy - GREEN Solar, Pontifical Catholic University of Minas Gerais - PUC Minas, Rua Dom Jose Gaspar no. 500, Predio 03, Sala 218 - Coracao Eucaristico 30535-610 Belo Horizonte - Minas Gerais, Brazil Article History: Received 28 October 2009; Revised 5 May 2010; Accepted 17 June 2010 Article Note: (miscellaneous) Communicated by: Associate Editor Elias Stefanakos

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.02.003 Byline: P. Geczy-Vig, I. Farkas Keywords: Solar thermal system; Thermal stratification; Water load; Modelling; Neural network Abstract: In this study an artificial neural network (ANN) model is introduced for modelling the layer temperatures in a storage tank of a solar thermal system. The model is based on the measured data of a domestic hot water system. The temperatures distribution in the storage tank divided in 8 equal parts in vertical direction were calculated every 5min using the average 5min data of solar radiation, ambient temperature, mass flow rate of collector loop, load and the temperature of the layers in previous time steps. The introduced ANN model consists of two parts describing the load periods and the periods between the loads. The identified model gives acceptable results inside the training interval as the average deviation was 0.22[degrees]C during the training and 0.24[degrees]C during the validation. Author Affiliation: Department of Physics and Process Control, Szent Istvan University, Pater K. u. 1., H-2103 GodollA, Hungary Article History: Received 21 January 2009; Revised 18 January 2010; Accepted 7 February 2010 Article Note: (miscellaneous) Communicated by: Associate Editor Halime Paksoy

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.11.004 Byline: Sergey L. Gratiy (a), Andrew C. Walker (b), Deborah A. Levin (a), David B. Goldstein (b), Philip L. Varghese (b), Laurence M. Trafton (b), Chris H. Moore (b) Keywords: Radiative transfer; Io; Atmospheres, Dynamics; Atmospheres, Structure; Satellites, Atmospheres Abstract: Conflicting observations regarding the dominance of either sublimation or volcanism as the source of the atmosphere on Io and disparate reports on the extent of its spatial distribution and the absolute column abundance invite the development of detailed computational models capable of improving our understanding of Io's unique atmospheric structure and origin. Improving upon previous models, Walker et al. (Walker, A.C., Gratiy, S.L., Levin, D.A., Goldstein, D.B., Varghese, P.L., Trafton, L.M., Moore, C.H., Stewart, B. [2009]. Icarus) developed a fully 3-D global rarefied gas dynamics model of Io's atmosphere including both sublimation and volcanic sources of SO.sub.2 gas. The fidelity of the model is tested by simulating remote observations at selected wavelength bands and comparing them to the corresponding astronomical observations of Io's atmosphere. The simulations are performed with a new 3-D spherical-shell radiative transfer code utilizing a backward Monte Carlo method. We present: (1) simulations of the mid-infrared disk-integrated spectra of Io's sunlit hemisphere at 19[mu]m, obtained with TEXES during 2001-2004; (2) simulations of disk-resolved images at Lyman-[alpha] obtained with the Hubble Space Telescope (HST), Space Telescope Imaging Spectrograph (STIS) during 1997-2001; and (3) disk-integrated simulations of emission line profiles in the millimeter wavelength range obtained with the IRAM-30m telescope in October-November 1999. We found that the atmospheric model generally reproduces the longitudinal variation in band depth from the mid-infrared data; however, the best match is obtained when our simulation results are shifted [approximately equal to]30[degrees] toward lower orbital longitudes. The simulations of Lyman-[alpha] images do not reproduce the mid-to-high latitude bright patches seen in the observations, suggesting that the model atmosphere sustains columns that are too high at those latitudes. The simulations of emission line profiles in the millimeter spectral region support the hypothesis that the atmospheric dynamics favorably explains the observed line widths, which are too wide to be formed by thermal Doppler broadening alone. Author Affiliation: (a) Department of Aerospace Engineering, Pennsylvania State University, University Park, PA 16802, USA (b) Department of Aerospace Engineering, University of Texas at Austin, Austin, TX 78712, USA Article History: Received 19 June 2009; Revised 29 October 2009; Accepted 4 November 2009

The relationship among the surface albedo, cloud properties, and radiative fluxes is investigated for the first time using a year-long cloud-resolving model (CRM) simulation with the prescribed evolving surface albedo. In comparison with the run using a fixed surface albedo, the CRM with the observed surface albedo represents the shortwave radiative budget closer to the observations in the winter. The greater surface albedo induces weaker instability in the low troposphere so that the amount of low clouds decreases during the winter. This reduces the shortwave and longwave cloud radiative forcing at the surface. The analysis of the CRM simulations with the evolving surface albedo reveals that there is a critical value (0.35) of the surface albedo. For albedos greater than the critical value, the upward shortwave flux at the top of the atmosphere (TOA) is positively proportional to the surface albedos when optically thin clouds exist, and is not much affected by reflection on the cloud top. If optically thick clouds occur and the surface albedo is greater than the critical value, the upward shortwave flux at the TOA is significantly influenced by the reflection of cloud top, but not much affected by the surface albedo. In addition, for albedos larger than the critical value, the downward shortwave flux at the surface is primarily influenced by the surface albedo and the reflection from the cloud base if optically thick clouds occur. However, the downward shortwave flux at the surface is not significantly affected by the surface albedo when optically thin clouds exist because the reflection on the cloud base is weak. When surface albedos are less than the critical value, those relationships among surface albedo, shortwave flux, and cloud properties are not obvious. The surface albedo effect on shortwave flux increases as solar zenith angle (SZA) decreases, but its dependence on the SZA is negligible when optically thick clouds exist. DOI: 10.1175/2009JAS3291.1

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2010.01.006 Byline: Wenjun Tang (a)(b), Kun Yang (a), Jie He (a)(b), Jun Qin (a) Keywords: Global radiation; Quality control; Sunshine duration; Hybrid model Abstract: Measurements of surface radiation in China are too sparse to meet demand for scientific research and engineering applications. Moreover, the radiation data often include erroneous and questionable values though preliminary quality-check has been done before the data release. Therefore, quality control of radiation data is often a prerequisite for using these data. In this study, a set of quality-check procedures were implemented to control the quality of the solar radiation measurements at 97 stations in China. A hybrid model for estimating global solar radiation was then evaluated against the controlled data. The results show that the model can estimate the global radiation with accuracy of MBE less than 1.5MJm.sup.-2 and RMSE less than 2.8MJm.sup.-2 for daily radiation and RMSE less than 2.0MJm.sup.-2 for monthly-mean daily radiation at individual stations over most of China except at a few stations where unsatisfactory estimates were possibly caused by severe air pollution or too dense clouds. The MBE averaged over all stations are about 0.7MJm.sup.-2 and RMSE about 2.0MJm.sup.-2 for daily radiation and RMSE about 1.3MJm.sup.-2 for monthly-mean daily radiation. Finally, this model was used to fill data gaps and to expand solar radiation data set using routine meteorological station data in China. This data set would substantially contribute to some radiation-related scientific studies and engineering applications in China. Author Affiliation: (a) Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China (b) Graduate School of Chinese Academy of Sciences, Beijing 100049, China Article History: Received 9 July 2009; Revised 29 December 2009; Accepted 6 January 2010 Article Note: (miscellaneous) Communicated by: Associate Editor Christian Gueymard

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.01.018 Byline: J. Polo (a), L.F. Zarzalejo (a), L. Martin (a), A.A. Navarro (a), R. Marchante (b) Keywords: Linke turbidity factor; Clear sky models; Solar radiation models Abstract: This work presents a methodology for estimating daily Linke turbidity factor for clear sky days from global horizontal irradiance information at solar noon and monthly mean values of the Linke turbidity factor. The analysis of the method proposed here have been made using the ESRA clear sky model to recalculate the direct normal irradiance using as input the new Linke turbidities. Ground data of three BSRN and six AEMet radiometric meteorological stations have been used for assessing the method. Linke turbidity factor estimated here exhibits higher fluctuations than the monthly means and the comparison of the solar irradiance recalculated with the ground data have shown a noticeable reduction of the root mean square deviation. On the other hand the new Linke turbidity estimations have been compared to those values obtained from normal beam irradiance measures. The discrepancies found point out the high dependence of the reliability of this method with the quality of the ground measurements used. Author Affiliation: (a) Renewable Energy Division (Energy Department), CIEMAT Avda. Complutense, 22, 28040 Madrid, Spain (b) Investigaciones y Recursos Solares Avanzados, IrSOLaV Santiago Grisolia, 2, 28760 Tres Cantos, Madrid, Spain Article History: Received 30 July 2008; Revised 22 January 2009; Accepted 24 January 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Christian Gueymard

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.01.004 Byline: G. Montero, J.M. Escobar, E. Rodriguez, R. Montenegro Keywords: Solar radiation; Beam, diffuse and reflected radiations; Clear-sky; Real-sky; Shadows; Adaptive meshes Abstract: In this work, we propose a numerical model for generating solar radiation maps with the use of 2-D adaptive meshes of triangles. These triangulations are constructed by using a refinement/derefinement procedure in accordance with the variations of terrain surface orography and albedo. This discretization has the advantage of defining the terrain characteristics with a minimum number of points, which reduces the computational cost for a given accuracy. Moreover, the model takes into account the effect of shadows for each time step, which are detected by analysing the crossing of the trajectory of the shaft of light with the triangles of the mesh. Thus, the solar radiation is first computed for clear-sky considering the different components of radiation, that is, beam, diffuse and reflected radiations. From the results of clear-sky radiation, the real-sky radiation is computed daily in terms of the clear-sky index. The maps of clear-sky index are obtained from a spatial interpolation of observational data that are available for each day at several points of the zone under consideration. Finally, the solar radiation maps of a month are calculated from the daily results. We illustrate the performance of the model with a numerical experiment related to an episode on the island of Gran Canaria. Author Affiliation: University Institute for Intelligent Systems and Numerical Applications in Engineering, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira, 35017 Las Palmas de Gran Canaria, Spain Article History: Received 25 March 2008; Revised 4 January 2009; Accepted 7 January 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.01.013 Byline: Somsak Chaiyapinunt, Supakit Worasinchai Keywords: Venetian blind; Optical properties; Slat curvature and thickness; Radiosity method; Mathematical model Abstract: This article is about the development of a mathematical model for a venetian blind. The model is used for determining the performance of the glass window installed with a venetian blind in term of heat transmission. The blind, whose optical properties are considered nonspecular, is modeled as an effective layer. The optical properties of the effective layer are mainly dependent on the slat angle, slat properties and solar profile angle. The effect of slat curvature and the effect of slat thickness are included in the developed model. The shortwave optical properties of the effective layer, transmittance, reflectance and absorptance, are classified as the optical properties for direct radiation and the optical properties for diffuse radiation. The analysis for optical properties due to the interreflection of the direct radiation between the adjacent slat surfaces is done by using radiosity method on a 6 surface closed enclosure. The effect of the slat curvature and thickness causes the shaded area blocked by the blind itself increased in certain cases. The optical properties for diffuse radiation of the effective layer are determined considering the incident diffuse radiation from the sky and from the ground. The optical properties calculated from the developed model are also compared to the results obtained from the three previous models. The validation of the results predicted by the developed mathematical model is performed by comparing the predicted results with the experimental results. The results that used to validate in this study is the ratio of the transmitted radiation through the glass window installed with venetian blind to the incident radiation on the glass window. It is shown from the comparison that the developed mathematical model for the venetian blind included the curvature and thickness effect yields quite accurate predicted results. Author Affiliation: Department of Mechanical Engineering, Faculty of Engineering, Chulalongkorn University, Phayathai, Bangkok 10330, Thailand Article History: Received 15 October 2007; Revised 7 November 2008; Accepted 23 January 2009 Article Note: (miscellaneous) Communicated by: Associate Editor Matheos Santamouris

This paper describes a procedure for experimental determination of metastable and resonant populations along a surface wave argon plasma column at atmospheric pressure. As modeling work progresses extensively, an experimental database is necessary to confirm these models. Obtained results, within the range of values reported in literature, indicate that densities of metastable and resonant levels grow along the plasma column for positions near the energy coupler device, where the energy of the surface wave which creates discharge is the highest. This behavior is also found for electron density and temperature; however, it is not the same for gradient. Therefore, at atmospheric pressure, populations of 4s levels are not only controlled by collision with electrons from ground state, but the dissociative recombination mechanism is also important, in agreement with results found by other authors using collisional-radiative models. Index Terms--Argon, atmospheric pressure, metastable atoms, optical spectroscopy, plasmas, self-absorption.