Search results for "Spectral power distribution"
showing 10 items of 13 documents
Analyzing the feasibility of time correlated spectral entropy for the assessment of neuronal synchrony
2016
In this paper, we study neuronal network analysis based on microelectrode measurements. We search for potential relations between time correlated changes in spectral distributions and synchrony for neuronal network activity. Spectral distribution is quantified by spectral entropy as a measure of uniformity/complexity and this measure is calculated as a function of time for the recorded neuronal signals, i.e., time variant spectral entropy. Time variant correlations in the spectral distributions between different parts of a neuronal network, i.e., of concurrent measurements via different microelectrodes, are calculated to express the relation with a single scalar. We demonstrate these relati…
Lighting in educational environments: An example of a complete analysis of the effects of daylight and electric light on occupants
2013
Abstract Light induces not only visual responses but also non-visual effects, indeed it affects performance, mood, attention and influences the synchronization of the biological clock. Duration, timing, intensity and the spectral power distribution of the light that reaches the eyes can have influence on human circadian rhythm and consequently on health. Given the important impact of the non-visual responses on people wellbeing, developing a model that allows lighting designers to predict them is a fundamental goal. In this paper a case study is reported: a series of measurements were carried out in a University classroom in order to study daylight and electric light characteristics and als…
Analysis of spectral irradiance distribution for PV applications at high latitude
2020
The spectral distribution of global tilted irradiance measured in Grimstad, Norway, is analyzed in terms of the average photon energy ( $APE$ ) blue fraction ( $BF$ ) and useful fraction ( $UF$ ). The results based on eight months of recorded data show a general shift of the $APE,\ BF$ , and $UF$ values to higher values than reference AM1.5G spectrum, with 1.63 eV, 0.45, and 0.88 being the average indices, respectively. The statistical coefficient of variation ( $CV$ ) is used to determine the variation of indices. The $CV$ for $APE,\ BF$ , and $UF$ are calculated to be 20.1%, 26.1%, and 25.7%, respectively confirming the earlier findings on $APE$ being a more accurate index for the quantif…
Indoor artificial lighting: Prediction of the circadian effects of different spectral power distributions.
2014
The study presented in this paper aims to evaluate if and how the environment affects the circadian impact of a light source by predicting circadian stimulus (CS) resulting from the exposure to different light scenes, using equations reported in studies by Rea et al. The main findings are: (1) Above 600 lx at eye level the increase of CS is little; (2) Between 50 lx and 200 lx at the eye level an increase of only 50 lx determines a significant increase of CS; (3) Light sources with correlated colour temperatures between 2900 K and 4200 K have similar impacts on the circadian system according to the calculation method used; (4) Even an almost neutral environment affects the circadian impact…
Modelling and analysis of the influence of solar spectrum on the efficiency of photovoltaic modules
2021
Abstract The article presents the influence of changes in the solar radiation spectrum distribution on the properties of various photovoltaic modules, with particular emphasis on the scattered component. We compared the relative efficiency of the photovoltaic modules based on various semiconductor absorbers during bright and sunny, and cloudy summer days. Additionally, we presented the impact of the module tilt angle on the magnitude of the surface incident scattered component and on the efficiency of the module. The solar spectra for various weather conditions were estimated using specialised computer programmes,such as SolarSpectrum or SMARTS2, and we present here the validation results f…
Calculations and measurements of the spectral radiance of the solar aureole
1968
The application of the theory of primary scattering to describe and interpret the spectral distribution of the sky radiance is discussed. It is shown that within the solar aureole the influence of the scattering of higher order can be neglected. Theoretical calculations of the spectral distribution of the sky radiance, carried out by Bullrich et al . (1965) based on an exponential aerosol size distribution with an upper limiting particle radius r = 10 ?, have been extended to r = 150 ?. The detailed study of the influence of these “giant” particles revealed that aerosol particles of r >30 ? have no effect on the sky radiation any more. Representative measurements taken at Mainz, Germany, at…
Continuum generation by dark solitons
2009
We demonstrate that the dark soliton trains in optical fibers with a zero of the group velocity dispersion can generate broad spectral distribution (continuum) associated with the resonant dispersive radiation emitted by solitons. This radiation is either enhanced or suppressed by the Raman scattering depending on the sign of the third order dispersion.
Spectral distribution and Coulomb correction for nuclear bremsstrahlung induced by heavy targets
2021
Abstract Bremsstrahlung spectra below 250 MeV have been measured colliding 500 MeV–electrons with Cu, Ag, and Au targets. The experimental intensity ratios relative to Cu are well described by an accurate analytical high-energy theory, which accounts both for Coulomb distortion and screening. This represents the first experimental verification of the discovery by Bethe-Maximon that leading-order quantum mechanical calculations, equivalent to quasiclassical approximations, become exact at high energies and small angles. It also shows that radiative QED effects play a minor role in the covered part of the spectral distribution within the accuracy (1.6%) of the present measurements.
Uniqueness verification of blue fraction as a parameter of spectral irradiance quantification
2021
The spectral distribution of global irradiance is measured in the optimal tilt (45° south) plane of array for the calender year 2020 in Grimstad, Norway. In this work the spectral distribution is quantified in terms of the Blue Fraction (BF). The uniqueness of BF has been tested and reported using the same methodology used for uniqueness verification of average photon energy (APE). The results show that the coefficient of correlation between the APE and BF was 0.98, meaning a possible bijective relation between these two parameters whereby both indicate a similar spectrum. The percentage contribution of integrated irradiance (Rc) was calculated for 25 nm wavelength bins for the BF region 35…
Description of x-ray beams using the fluorescence yields of a set of thick targets
1995
Quantitative methods in x-ray fluorescence analysis require a knowledge of the spectral distribution of the fluorescence-exciting beam. The use of XRF yield measurements of a set of thick pure element targets is proposed for the description of a fluorescence-exciting x-ray beam, without the need to obtain its spectral distribution. This new approach is derived theoretically and verified by comparing thin-target yields calculated from XRF yield measurements of thick pure element specimens with those obtained from a calculated spectral distribution. The difference between the two methods of obtaining the thin-target yields is within 9% relative error.