Search results for " Character"
showing 10 items of 1756 documents
Warm white LED light by frequency down-conversion of mixed yellow and red Lumogen®
2013
This work reports on the benefits and promising opportunities offered by white LED hybrid technology, based on a mixing perylene-based dyes in order to obtain a warm white light for frequency-down conversion. In a standard Ce:YAG-based white LED, the white light appears cold due to the weakness of red wavelength components in the emission spectrum. In order to obtain a warmer white, one possible solution is to add a red phosphor to the yellow one to move the chromatic coordinates properly, though the luminous efficiency drastically decreases due to the increased light absorption of the coating layer. It is generally believed that the low efficiency of warm white LEDs is the main issue today…
Influence of biotic and abiotic factors on soil organic matter dynamics assessed by the biogeochemical characterisation of soluble organic matter
2014
Soils are the greatest reservoir of C on the continents, and organic matter mineralisation bymicrobial activity represents the major part of the CO2 emitted by terrestrial ecosystems.In this work, we studied water-extractable organic matter (WEOM), which corresponds to themore reactive fraction of soil organic matter (SOM). Our objectives were (i) to identify therelationships of WEOM dynamics with bacterial communities, and with soil physico-chemicalparameters; (ii) to provide a precise chemical characterisation of WEOM.There is a strong link between SOM solubility and the structure of bacterial communities, andan erosion of their diversity has an impact on SOM and WEOM dynamics, and leads …
Gully Erosion Susceptibility Mapping Using Multivariate Adaptive Regression Splines—Replications and Sample Size Scenarios
2019
Soil erosion is a serious problem affecting numerous countries, especially, gully erosion. In the current research, GIS techniques and MARS (Multivariate Adaptive Regression Splines) algorithm were considered to evaluate gully erosion susceptibility mapping among others. The study was conducted in a specific section of the Gorganroud Watershed in Golestan Province (Northern Iran), covering 2142.64 km2 which is intensely influenced by gully erosion. First, Google Earth images, field surveys, and national reports were used to provide a gully-hedcut evaluation map consisting of 307 gully-hedcut points. Eighteen gully erosion conditioning factors including significant geoenvironmental and morph…
Modeling a non-stationary bots’ arrival process at an e-commerce Web site
2017
Abstract The paper concerns the issue of modeling and generating a representative Web workload for Web server performance evaluation through simulation experiments. Web traffic analysis has been done from two decades, usually based on Web server log data. However, while the character of the overall Web traffic has been extensively studied and modeled, relatively few studies have been devoted to the analysis of Web traffic generated by Internet robots (Web bots). Moreover, the overwhelming majority of studies concern the traffic on non e-commerce websites. In this paper we address the problem of modeling a realistic arrival process of bots’ requests on an e-commerce Web server. Based on real…
On Non-Gaussian limiting laws for certain statistics of Wigner Matrices
2013
This paper is a continuation of our papers [12-14] in which the limiting laws of fluctuations were found for the linear eigenvalue statistics Tr j(M(n)) and for the normalized matrix elements √n̅jjj(M(n)) of differentiable functions of real symmetric Wigner matrices M(n) as n →∞. Here we consider another spectral characteristic of Wigner matrices, xnA [j] = Tr j(M(n))A(n), where {A(n)}∞n=1 is a certain sequence of non-random matrices. We show first that if M(n) belongs to the Gaussian Orthogonal Ensemble, then xnA [j] satisfies the Central Limit Theorem. Then we consider Wigner matrices with i.i.d. entries possessing the entire characteristic function and find the limiting probability law f…
Vitamins in wine: Which, what for, and how much?
2021
Vitamins are essential compounds to yeasts, and notably in winemaking contexts. Vitamins are involved in numerous yeast metabolic pathways, including those of amino acids, fatty acids, and alcohols, which suggests their notable implication in fermentation courses, as well as in the development of aromatic compounds in wines. Although they are major components in the course of those microbial processes, their significance and impact have not been extensively studied in the context of winemaking and wine products, as most of the studies focusing on the subject in the past decades have relied on relatively insensitive and imprecise analytical methods. Therefore, this review provides an extensi…
INNOVAZIONE DEI MATERIALI NATURALI: TERRA E NANOTUBI DI ARGILLA PER UNA SFIDA SOSTENIBILE
2019
All’interno del dibattito culturale che vede la questione ambientale come prioritaria e con riferimento a studi e ricerche che negli ultimi anni hanno promosso materiali compositi a base di terra cruda, gli Autori, consapevoli della necessità che il rapporto fra Progetto e Materia debba assumere una nuova centralità supportato dalle specificità della Tecnologia dell’Architettura, illustrano le risultanze di una sperimentazione che ha l’obiettivo di migliorare le prestazioni della terra cruda con l’apporto delle nanotecnologie, sviluppando un ‘nuovo materiale’ con una ridotta embodied energy e una ridotta quantità di emissioni di CO2 in atmosfera.
Performance improvement of a Savonius water rotor with novel blade shapes
2021
Abstract Savonius water rotor is a prominent drag based turbine able to extract energy available in flowing water with low velocity like river streams, tidal currents or other man made water canals. However, in view of its low performance, an enhanced design of the rotor blades is necessary to better its efficiency. Therefore, the present study aims to improve the efficiency of Savonius rotor by changing the blade design. Different blade shapes were investigated numerically using computational fluid dynamics (CFD). Using conventional design, the peak power coefficient was found to be 0.166 at tip-speed ratio of 0.78. However, the peak power coefficient reaches 0.184 using the optimal blade …
Filters for X-Ray Detectors on Space Missions
2022
Thin filters and gas-tight windows are used in space to protect sensitive X-ray detectors from out-of-band electromagnetic radiation, low-energy particles, and molecular contamination. Though very thin and made of light materials, filters are not fully transparent to X-rays. For this reason, they ultimately define the detector quantum efficiency at low energies. In this chapter, we initially provide a brief overview of filter materials and specific designs adopted on space experiments with main focus on detectors operating at the focal plane of grazing incidence X-ray telescopes. We then provide a series of inputs driving the design and development of filters for high-energy astrophysics sp…