332 research outputs found
A new correlation between global solar energy radiation and daily temperature variations
No full textThe energy balance for an atmospheric layer near the soil is evaluated. By integrating it over the whole day period, a linear relationship between the global daily solar radiation on a horizontal surface and the product of the sunshine hours at clear sky with the daily maximum temperature variation is achieved. The results for the monthly averaged daily values show a comparable accuracy with some well recognized models such as the Ångström-Prescott one, at least for Mediterranean climatic area. Validation of the results has been performed using old data sets which are almost contemporary and relative to the same sites with the ones used for the comparison. © 2015 Elsevier Ltd
Second international spectroradiometer intercomparison: Results and impact on PV device calibration
No full textThis paper describes the results of an intercomparison of spectroradiometers for measuring global normal incidence and direct normal incidence spectral irradiance in the visible and in the near infrared, together with an assessment of the impact these results may have on the calibration of the short circuit current (Isc) of triple-junction photovoltaic devices and on the relevant spectral mismatch calculation. The intercomparison was conducted by six European scientific laboratories and a Japanese industrial partner. Seven spectroradiometer systems, for a total of 13 different instruments/channels using two different technologies and made by four different manufacturers were involved. This group of systems represents a good cross section of the instrumentation for solar spectrum measurements available to date. The instruments were calibrated by each partner prior to the intercomparison following their usual procedure and traceability route in order to verify the entire measurement and traceability chain. The difference in measured spectral irradiance showed to have an impact on the calibration of a set of Iso-Type cells varying from ±2% to ±14% for middle and bottom cell, respectively. Copyright © 2014 John Wiley & Sons, Ltd
Concurrent contributions of ascending cerebellar and basal forebrain cholinergic outputs to the regulation of spatial learning
No full textConcurrent contributions of ascending cerebellar and basal forebrain cholinergic outputs in the regulation of spatial learning
No full textOn the vibration analysis of off-road vehicles: Influence of terrain deformation and irregularity
No full textSurface irregularity acts as a major excitation source in off-road driving that induces vibration of the vehicle body through the tire assembly and the suspension system. When adding ground deformability, this excitation is modulated by the soil properties and operating conditions. The underlying mechanisms that govern ground behavior can be explained and modeled drawing on Terramechanics. Based on this theory, a comprehensive quarter-car model of off-road vehicle is presented that takes into account tire/soil interaction. The model can handle the general case of compliant wheel rolling on compliant ground and it allows ride and road holding performance to be evaluated in the time and frequency domain.
An extensive set of simulation tests is included to assess the impact of various surface roughness and ground deformability through a parameter study, showing the potential of the proposed model to describe the behavior of off-road vehicles for design and performance optimization purposes
Soiling Detection Investigation in Solar Irradiance Sensors Systems
No full textDirt deposition on solar irradiance measurement instruments can lead to errors in radiationmeasurements and, as a result, in incorrect energy production management issues. Climate and meteorological conditions may affect in different way the deposition process and thus, soiling severity and type are geographical and time-dependent. To investigate the soiling impact, here we describe a methodology that allows estimating the effect of dirt deposition on solar irradiance measurement systems, e.g., pyrheliometer. The methodology relies on the evaluation of a soiling index, based on pyranometer data measurements and it has been in field validated, using a solar irradiance measurement system deployed at ENEA Research Center of Portici. The results show that, under suitable assumptions, the computed index may be used to obtain a reasonable estimation of soiling effect
ON THE VERTICAL DYNAMICS MODELLING OF RIGID WHEELS ON SOFT SOIL
No full textRigid wheels or wheels much stiffer with respect to the soil are used in many applications in the field of Terramechanics, e.g., planetary exploration rovers or agricultural vehicles on ploughed terrains. In this study vertical ground forces exchanged between a rigid wheel and a soft terrain are investigated. Useful and novel information on off-road vehicles behaviour in terms of vibrations, dynamic wheel sinkage, terrain hardness and so forth are obtained. According to the derived wheel-soil interaction model, a Quarter Car (QC) system relative to off-road vehicles with rigid wheels is established and its behaviour under different scenarios (which include different terrains with different surface roughness) is investigated. The results achieved for the off-road vertical dynamics can be relevant for vehicles design. Furthermore, as an example of a real application, a model-based observer grounded on this QC system is adopted in order to estimate the terrain hardness
Comparative Analysis of Ground-Based Solar Irradiance Measurements and Copernicus Satellite Observations
No full textSolar irradiance data provided by the Copernicus program are crucial for several scientific, environmental, and energy management applications, but their validation by means of ground-based measurements may be necessary, especially if daily and hourly data resolutions are required. The validation process not only ensures that reliable information is available for solar energy resource planning, power plant performance assessment, and grid integration, but also contributes to the improvement of the Copernicus system itself. Ground-based stations offer site-specific data, allowing for comprehensive assessments of the system’s performance. This work presents a comparative statistical analysis of solar irradiance data provided by the Copernicus system and ground-based measurements on a seasonal basis at three specific Italian reference sites, showing a maximum average relative error of less than 7% for hourly horizontal global irradiance in the irradiance range defined by the IEC 61724-2
Estratigrafía del Paleozoíco inferior en Aguada de los Azulejitos, Provincia de San Juan, Argentina
No full textFil: Hugo, Carlos A. Ministerio de Economía. Secretaría de Minería. Servicio Geológico Nacional y Servicio Minero Nacional; Argentina.Fil: Leanza Héctor A. Ministerio de Economía. Secretaría de Minería. Servicio Geológico Nacional y Servicio Minero Nacional; Argentina.Fil: Marchese, Humberto G. Ministerio de Economía. Secretaría de Minería. Servicio Geológico Nacional y Servicio Minero Nacional; Argentina
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