393 research outputs found
Performance of a large limited streamer tube cell in drift mode
The performance of a large (3x3 ) streamer tube cell in drift mode is
shown. The detector space resolution has been studied using cosmic muons
crossing an high precision silicon telescope. The experimental results are
compared with a GARFIELD simulation.Comment: 18 pages, 7 figures. Accepted by Nucl. Instr. and Methods
Sustainability perspectives: a new methodological approach for quantitative assessment
This paper proposes a new tool to assess sustainability and make the concept
of sustainable development operational. It considers its multi-dimensional
structure combining the information deriving from a selection of relevant
sustainability indicators belonging to economic, social and environmental
pillars. The main novelties of this approach are the modelling framework, a
recursive-dynamic computable general equilibrium used to calculate the trend
of all indicators over time throughout the world, and the aggregation
methodology to reconcile them in one aggregate index to measure overall
sustainability. The former allows capturing the sector and regional
interactions and higher-order effects driven by background assumptions on
relevant variables to depict future scenarios. The latter makes it possible to
compare sustainability performances, under alternative scenarios, across
countries and over time. Main results show that the current sustainability at
world level differs from what the traditional measure of well-being, the GDP,
depicts, highlighting the trade-offs among different components of
sustainability. Moreover, in the next decade a slight decrease in world
sustainability may occur, in spite of an expected increase in world domestic
product. Finally, dedicated policies increase overall sustainability, showing
that social and environmental benefits may be greater than the correlated
economic costs
Verification and Calibration of a Reduced Order Wind Farm Model by Wind Tunnel Experiments
In this paper an adaptation of the FLORIS approach is considered that models the wind flow and power production within a wind farm. In preparation to the use of this model for wind farm control, this paper considers the problem of its calibration and validation with the use of experimental observations. The model parameters are first identified based on measurements performed on an isolated scaled wind turbine operated in a boundary layer wind tunnel in various wind-misalignment conditions. Next, the wind farm model is verified with results of experimental tests conducted on three interacting scaled wind turbines. Although some differences in the estimated absolute power are observed, the model appears to be capable of identifying with good accuracy the wind turbine misalignment angles that, by deflecting the wake, lead to maximum power for the investigated layouts
Fatigue strength of austempered ductile iron-to-steel dissimilar arc-welded joints
Nowadays, the use of different classes of materials in the same structure is increased to keep pace with innovation and high structural performances. In this context, structural components made of different materials need to be joined together and a possible solution is given by arc welding. Dissimilar welded joints must often be able to withstand fatigue loads; however, Design Standards provide fatigue strength categories only for homogeneous welded joints. The aim of the present paper is to compare the fatigue behaviour of EN-GJS-1050 austempered ductile iron-to-S355J2 steel dissimilar joints to the categories of the corresponding homogeneous steel welded joints, as suggested in International Standards and Recommendations. For this purpose, experimental fatigue tests were performed on a selection of dissimilar welded details. First, the microstructure was identified by metallographic analysis; micro-hardness measurements were collected and residual stress profiles were obtained by using the X-ray diffraction technique on a selection of joints. Misalignments were quantified for all specimens. Then, experimental fatigue tests have been performed on a number of joint geometries subject to axial or bending fatigue loadings and tested in the as-welded conditions. The fracture surfaces of the joints have been analysed to locate fatigue crack nucleation sites
An infrared diagnostic for magnetism in hot stars
Magnetospheric observational proxies are used for indirect detection of
magnetic fields in hot stars in the X-ray, UV, optical, and radio wavelength
ranges. To determine the viability of infrared (IR) hydrogen recombination
lines as a magnetic diagnostic for these stars, we have obtained low-resolution
(R~1200), near-IR spectra of the known magnetic B2V stars HR 5907 and HR 7355,
taken with the Ohio State Infrared Imager/Spectrometer (OSIRIS) attached to the
4.1m Southern Astrophysical Research (SOAR) Telescope. Both stars show definite
variable emission features in IR hydrogen lines of the Brackett series, with
similar properties as those found in optical spectra, including the derived
location of the detected magnetospheric plasma. These features also have the
added advantage of a lowered contribution of stellar flux at these wavelengths,
making circumstellar material more easily detectable. IR diagnostics will be
useful for the future study of magnetic hot stars, to detect and analyze
lower-density environments, and to detect magnetic candidates in areas obscured
from UV and optical observations, increasing the number of known magnetic stars
to determine basic formation properties and investigate the origin of their
magnetic fields.Comment: 4 pages, accepted for publication in A&
Crescimento de cultivares de marmeleiro enxertados sobre o porta-enxerto japonês em condições de campo.
Época de coleta das estacas, do uso de fitorregulador de enraizamento e de diferentes tipos de enxertos na produção de mudas de figueira Roxo de Valinhos.
Sustainable Solvent-Free Selective Oxidation of Benzyl Alcohol Using Ru(0) Supported on Alumina
The selective oxidation of primary alcohols into their corresponding carbonyl compounds is challenging because of the easy over oxidization to acids and esters. The traditional reaction requires large amounts of solvent and oxidant, causing serious environmental issues. Recently, several efforts have been made to transform the reaction into a more sustainable process. Here, we investigated the solvent-free oxidation of benzyl alcohol using air as a green oxidant in the presence of ruthenium supported on alumina and zirconia, thereby meeting atom economy and environmental requirements. The materials were extensively characterized and, in addition to their activity, selectivity, and reusability, the environmental sustainability of the process was assessed according to green chemistry metrics. XRD, TEM, and XPS analyses suggest that the formation of metallic Ru on the support plays a key role in the catalytic activity. Ru supported on alumina, after a reduction treatment, achieves good activity (62% conversion) and a complete selectivity in a very sustainable process (without a solvent and with air as oxidant), as indicated by the very low E-factor value. The formulation is very stable and maintains high activity after recycling
Produção de mudas de pêra por dupla-enxertia em interenxertos de marmeleiro utilizando o porta-enxerto japonês.
Experimental and Theoretical Investigation of Ion Pairing in Gold(III) Catalysts
The ion pairing structure of the possible species present in solution during the gold(III)-catalyzed hydration of alkynes: [(ppy)Au(NHC)Y]X2 and [(ppy)Au(NHC)X]X [ppy = 2-phenylpyridine, NHC = NHCiPr = 1,3-bis(2,6-di-isopropylphenyl)-imidazol-2-ylidene; NHC = NHCmes = 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene X = Cl-, BF4-, OTf-; Y = H2O and 3-hexyne] are determined. The nuclear overhauser effect nuclear magnetic resonance (NMR) experimental measurements integrated with a theoretical description of the system (full optimization of different ion pairs and calculation of the Coulomb potential surface) indicate that the preferential position of the counterion is tunable through the choice of the ancillary ligands (NHCiPr, NHCmes, ppy, and Y) in [(ppy)Au(NHC)(3-hexyne)]X2 activated complexes that undergo nucleophilic attack. The counterion can approach near NHC, pyridine ring of ppy, and gold atom. From these positions, the anion can act as a template, holding water in the right position for the outer-sphere attack, as observed in gold(I) catalysts
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