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S W Glunz - One of the best experts on this subject based on the ideXlab platform.
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impact of the firing Temperature Profile on light induced degradation of multicrystalline silicon
Physica Status Solidi-rapid Research Letters, 2016Co-Authors: Rebekka Eberle, Wolfram Kwapil, Florian Schindler, Martin C Schubert, S W GlunzAbstract:Light- and elevated Temperature-induced degradation in multicrystalline silicon can reduce the efficiency of solar cells significantly. In this work, the influence of the firing process and its Temperature Profile on the degradation behaviour of neighbouring mc-Si wafers is analysed. Five Profiles with measured high peak Temperatures ≥800 °C and varying heating and cooling ramps are examined. With spatially resolved and lifetime calibrated photoluminescence images, normalized defect concentrations N*t are calculated to determine the degradation intensity. Wafers that underwent a fast firing process typical for industrial solar cell production show a significantly stronger degradation than samples that were subjected to the same peak Temperature but with slower heating and cooling rates. A spatially resolved analysis of the carrier lifetime in the whole wafer shows that the degradation begins in low lifetime areas around dislocation clusters, spreading into good grains after several hours. By the use of optimized ramp-up and/or ramp-down rates during the firing even at very high peak Temperatures, light and elevated Temperature induced degradation can be suppressed. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)
Bifang Liu - One of the best experts on this subject based on the ideXlab platform.
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modelling accretion disc emission with generalized Temperature Profile and its effect on agn spectral energy distribution
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: Huaqing Cheng, Weimin Yuan, Heyang Liu, A A Breeveld, Chichuan Jin, Bifang LiuAbstract:The broadband spectral energy distribution (SED) of Active Galactic Nuclei (AGN) is investigated for a well-selected sample composed of $23$ Seyfert 1 galaxies observed simultaneously in the optical/UV and X-ray bands with the Neil Gehrels {\it Swift} Observatory. The optical to UV continuum spectra are modeled, for the first time, with emission from an accretion disk with a generalized radial Temperature Profile, in order to account for the intrinsic spectra which are found to be generally redder than the model prediction of the standard Shakura-Sunyaev disk (SSD) ($F_\nu\propto\nu^{+1/3}$). The power-law indices of the radial Temperature Profile ($T_{\rm eff}(R)\propto R^{-p}$, $R$ is the radius of the accretion disk) are inferred to be $p=0.5$ -- $0.75$ (a median of $0.63$), deviating from the canonical $p=0.75$ for the SSD model as widely adopted in previous studies. A marginal correlation of a flatter radial Temperature Profile (a smaller $p$ value) with increasing the Eddington ratio is suggested. Such a model produces generally a lower peak of accretion disk emission and thus a smaller bolometric luminosity in some of the AGN, particularly those with high Eddington ratios, than that based on the SSD model by a factor of several. The broadband SED, the bolometric correction factors and their dependence on some of the AGN parameters are re-visited. We suggest that such non-standard SSD disks may operate in AGN and are at least partly responsible for the reddened optical/UV spectra as observed. One possible explanation for these flattened Temperature Profiles is the mass loss process in form of disk winds/outflows.
Yutaka Fujita - One of the best experts on this subject based on the ideXlab platform.
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suzaku measurement of abell 2204 s intracluster gas Temperature Profile out to 1800 kpc
Astronomy and Astrophysics, 2009Co-Authors: Thomas H Reiprich, Daniel S Hudson, Y Y Zhang, Kosuke Sato, Yoshitaka Ishisaki, Akio Hoshino, Takaya Ohashi, Naomi Ota, Yutaka FujitaAbstract:Context. Measurements of intracluster gas Temperatures out to large radii, where much of the galaxy cluster mass resides, are important for using clusters for precision cosmology and for studies of cluster physics. Previous attempts to measure robust Temperatures at cluster virial radii have failed. Aims. The goal of this work is to measure the Temperature Profile of the very relaxed symmetric galaxy cluster Abell 2204 out to large radii, possibly reaching the virial radius. Methods. Taking advantage of its low particle background due to its low-Earth orbit, Suzaku data are used to measure the outer Temperature Profile of Abell 2204. These data are combined with Chandra and XMM-Newton data of the same cluster to make the connection to the inner regions, unresolved by Suzaku, and to determine the smearing due to Suzaku’s point spread function. Results. The Temperature Profile of Abell 2204 is determined from ∼10 kpc to ∼1800 kpc, close to an estimate of r200 (the approximation to the virial radius). The Temperature rises steeply from below 4 keV in the very center up to more than 8 keV in the intermediate range and then decreases again to about 4 keV at the largest radii. Varying the measured particle background normalization artificially by ±10% does not change the results significantly. Several additional systematic effects are quantified, e.g., those due to the point spread function and astrophysical fore- and backgrounds. Predictions for outer Temperature Profiles based on hydrodynamic simulations show good agreement. In particular, we find the observed Temperature Profile to be slightly steeper but consistent with a drop of a factor of 0.6 from 0.3 r200 to r200, as predicted by simulations. Conclusions. Intracluster gas Temperature measurements up to r200 seem feasible with Suzaku, after a careful analysis of the different background components and the effects of the point spread function. Such measurements now need to be performed for a statistical sample of clusters. The result obtained here indicates that numerical simulations capture the intracluster gas physics well in cluster outskirts.
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suzaku measurement of abell 2204 s intracluster gas Temperature Profile out to 1800 kpc
arXiv: Astrophysics, 2008Co-Authors: Thomas H Reiprich, Daniel S Hudson, Y Y Zhang, Kosuke Sato, Yoshitaka Ishisaki, Akio Hoshino, Takaya Ohashi, Naomi Ota, Yutaka FujitaAbstract:Context: Measurements of intracluster gas Temperatures out to large radii are important for the use of clusters for precision cosmology and for studies of cluster physics. Previous attempts to measure robust Temperatures at cluster virial radii failed. Aims: The goal of this work is to measure the Temperature Profile of the very relaxed galaxy cluster Abell 2204 out to large radii, possibly reaching the virial radius. Methods: Taking advantage of its low particle background due to its low-Earth orbit, Suzaku data are used to measure the outer Temperature Profile of Abell 2204. These data are combined with Chandra and XMM-Newton data of the same cluster in order to make the connection to the inner regions, unresolved by Suzaku, and to determine the smearing due to Suzaku's PSF. Results: The Temperature Profile of Abell 2204 is determined from 10 kpc to 1800 kpc, close to an estimate of r200 (the approximation to the virial radius). The Temperature rises steeply from below 4 keV in the very center up to more than 8 keV in the intermediate range and then decreases again to about 4 keV at the largest radii. Varying the measured particle background normalization artificially by +-10 percent does not change the results significantly. Predictions for outer Temperature Profiles based on hydrodynamic simulations show good agreement. In particular, we find the observed Temperature Profile to be slightly steeper but consistent with a drop of a factor of 0.6 from 0.3 r200 to r200, as predicted by simulations. Conclusions: Temperature measurements up to the virial radius seem feasible with Suzaku, when a careful analysis of the different background components and the effects of the PSF is performed. The result obtained here indicates that numerical simulations capture the intracluster gas physics well in cluster outskirts.
Fei Tang - One of the best experts on this subject based on the ideXlab platform.
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a global model of plume axial Temperature Profile transition from axisymmetric to line source pool fires in normal and reduced pressures
Fuel, 2014Co-Authors: Fei Tang, Zengwei Qiu, Qiang WangAbstract:Abstract The present work is an experimental investigation into the plume axial Temperature Profile of hydrocarbon pool fires from axisymmetrical to linear- source geometry in normal (100 kPa) and sub-atmospheric (64 kPa) pressures. Five rectangular pool with the same area S (36 cm 2 ) but different aspect ratios (long side divided by short side n = L/W = 1, 2, 3, 4, 8) are used. The plume axial Temperature rise of the pool fire at a given height was observed to be higher in the reduced pressure than that in the normal pressure atmosphere. With the increase in pool dimension aspect ratio, the Temperature power scaling law (Δ T ∼ z β ) decay index ( β ) transits from −5/3 (axisymmetric source) to −1 (line source). An exponential function is proposed to characterize such transition behavior in relation to the source aspect ratio of the pool fire, which is shown to be well verified by the experiments. A global model, with both ambient pressure and pool dimension aspect ratio accounted for, is then developed for the plume axial Temperature Profile of rectangular hydrocarbon pool fires.
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Axial Temperature Profile in vertical buoyant turbulent jet fire in a reduced pressure atmosphere
Fuel, 2013Co-Authors: Qiang Wang, Fei Tang, Michael A. Delichatsios, Xiaochun ZhangAbstract:Abstract Characteristics of a vertical jet fire in a reduced pressure atmosphere (at high altitude) have not been quantified in the literatures. In the reduced pressure atmosphere, the air/oxygen density is lower, which in turn affects both combustion and entrainment, and hence the axial Temperature Profile of a diffusive turbulent jet fire. Experiments have been conducted in this work to investigate the axial Temperature Profiles of propane turbulent buoyant jet fires produced by nozzles with diameters of 4–10 mm in both reduced- (0.64 atm) and normal pressure (1 atm) atmosphere. It is found that the maximum Temperature in the flame zone is a bit higher, the Temperature decreases faster vertically and is somewhat lower in the buoyant plume zone in the normal pressure than those in the reduced pressure. The virtual origin is then deduced and clarified to be larger in the reduced pressure, however, it can be correlated non-dimensionally with flame Froude number ( Fr f ) in a 2/5 power law function for both these two pressures. Finally, the normalized axial Temperature Profile against non-dimensional height above the virtual origin can be still well characterized into three regions in the reduced pressure by the same power law functions as those in the normal pressure.
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a mathematical model on lateral Temperature Profile of buoyant window spill plume from a compartment fire
International Journal of Heat and Mass Transfer, 2013Co-Authors: Fei Tang, Michael A. DelichatsiosAbstract:A Gaussian-based mathematical model is theoretically brought forward to describe the lateral Temperature Profile (in the direction normal to the facade wall) of a spill buoyant plume from window of a compartment fire. The model is built up physically based on that this buoyant plume is conceptually produced by a rectangular fire source with characteristic side dimensions of l1 (beside wall, physical length scale related to the effective area of the outflow) and l2 (normal to wall, physical length scale representing the length after which the outflow turns from horizontal to vertical due to buoyancy) sitting beside an adiabatic facade wall at the neutral plane height of the window. A deduced length scale, by accounting for the entrainment of air mass flow rate into the plume from the non-constrained sides, is brought forward to characterize the effective plume thickness in the direction normal to the facade wall, which will be used in the Gaussian Profile function. Experiments are carried out in an experimental device to validate the model developed for six different windows. Results show that the length scale proposed for describing the effective plume thickness can successfully collapse the experimental data of different total heat release rates for various window geometries, and the proposed Gaussian-based model can predict the lateral Temperature Profile measurements. Furthermore, an exponential function is proposed for the parameter β in the Gaussian Profile of such a spill plume in relation to the window aspect ratio (H/W).
Huaqing Cheng - One of the best experts on this subject based on the ideXlab platform.
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modelling accretion disc emission with generalized Temperature Profile and its effect on agn spectral energy distribution
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: Huaqing Cheng, Weimin Yuan, Heyang Liu, A A Breeveld, Chichuan Jin, Bifang LiuAbstract:The broadband spectral energy distribution (SED) of Active Galactic Nuclei (AGN) is investigated for a well-selected sample composed of $23$ Seyfert 1 galaxies observed simultaneously in the optical/UV and X-ray bands with the Neil Gehrels {\it Swift} Observatory. The optical to UV continuum spectra are modeled, for the first time, with emission from an accretion disk with a generalized radial Temperature Profile, in order to account for the intrinsic spectra which are found to be generally redder than the model prediction of the standard Shakura-Sunyaev disk (SSD) ($F_\nu\propto\nu^{+1/3}$). The power-law indices of the radial Temperature Profile ($T_{\rm eff}(R)\propto R^{-p}$, $R$ is the radius of the accretion disk) are inferred to be $p=0.5$ -- $0.75$ (a median of $0.63$), deviating from the canonical $p=0.75$ for the SSD model as widely adopted in previous studies. A marginal correlation of a flatter radial Temperature Profile (a smaller $p$ value) with increasing the Eddington ratio is suggested. Such a model produces generally a lower peak of accretion disk emission and thus a smaller bolometric luminosity in some of the AGN, particularly those with high Eddington ratios, than that based on the SSD model by a factor of several. The broadband SED, the bolometric correction factors and their dependence on some of the AGN parameters are re-visited. We suggest that such non-standard SSD disks may operate in AGN and are at least partly responsible for the reddened optical/UV spectra as observed. One possible explanation for these flattened Temperature Profiles is the mass loss process in form of disk winds/outflows.
