41,250 research outputs found
Some recent results of X-ray astronomy
X ray astronomy rocket experiment for identification and positioning of SCO X-1 strong X ray sourc
X-ray reflection collimator adapted to focus X-radiation directly on a detector Patent
X ray collimating structure for focusing radiation directly onto detecto
Experimental and numerical studies of ferritic stainless steel tubular cross sections under combined compression and bending
An experimental and numerical study of ferritic stainless steel tubular cross sections under combined loading is presented in this paper. Two square hollow section (SHS) sizesâSHS 40Ă40Ă240Ă40Ă2 and SHS 50Ă50Ă250Ă50Ă2 made of Grade EN 1.4509 (AISI 441) stainless steelâwere considered in the experimental program, which included 2 concentrically loaded stub column tests, 2 four-point bending tests, and 14 eccentrically loaded stub column tests. In parallel with the experimental investigation, a finite-element (FE) study was also conducted. Following validation of the FE models against the test results, parametric analyses were carried out to generate further structural performance data. The experimental and numerical results were analyzed and compared with the design strengths predicted by the current European stainless steel design code EN 1993-1-4 and American stainless steel design specification SEI/ASCE-8. The comparisons revealed that the codified capacity predictions for ferritic stainless steel cross sections under combined loading are unduly conservative. The deformation-based continuous strength method (CSM) has been extended to cover the case of combined loading. The applicability of CSM to the design of ferritic stainless steel cross sections under combined loading was also evaluated. The CSM was shown to offer substantial improvements in design efficiency over existing codified methods. Finally, the reliability of the proposals was confirmed by means of statistical analyses according to both the SEI/ASCE-8 requirements and those of EN 1990
Using global interpolation to evaluate the Biot-Savart integral for deformable elliptical Gaussian vortex elements
This paper introduces a new method for approximating the Biot-Savart integral for elliptical Gaussian functions using high-order interpolation and compares it to an existing method based on small aspect ratio asymptotics. The new evaluation technique uses polynomials to approximate the kernel corresponding to the integral representation of the streamfunction. We determine the polynomial coefficients by interpolating precomputed values from look-up tables over a wide range of aspect ratios. When implemented in a full nonlinear vortex method, we find that the new technique is almost three times faster and unlike the asymptotic method, provides uniform accuracy over the full range of aspect ratios. As a proof-of-concept for large scale computations, we use the new technique to calculate inviscid axisymmetrization and filamentation of a two-dimensional elliptical fluid vortex. We compare our results with those from a pseudo-spectral computation and from electron vortex experiments, and find good agreement between the three approaches
Estimation of temporal and spatial variations in groundwater recharge in unconfined sand aquifers using Scots pine inventories
Acknowledgements. This study was made possible through funding from the EU 7th Framework programme GENESIS (contract number 226536), AQVI project (no. 128377) in Academy of Finland AKVA research programme, the Renlund Foundation, VALUE doctoral school and Maa- ja vesitekniikan tuki ry. We would like to express our gratitude to Geological survey of Finland, Finnish Forest Administration (MetsÀhallitus) and Finnish Forest Centre (MetsÀkeskus), Finnish meteorological institute, Finnish environmental administration and National land survey of Finland for providing data sets and expert knowledge that made this study possible in its current extent. To reproduce the research in the paper, data from above-mentioned agencies can be made available for purchase on request from the corresponding agency, other data can be provided by the corresponding author upon request. We thank Per-Erik Jansson for his assistance with the CoupModel and Jarkko Okkonen (GTK), anonymous reviewer, and Angelo Basile for their critical comments that significantly improved the manuscript.Peer reviewedPublisher PD
Uncertainty in Soft Temporal Constraint Problems:A General Framework and Controllability Algorithms forThe Fuzzy Case
In real-life temporal scenarios, uncertainty and preferences are often
essential and coexisting aspects. We present a formalism where quantitative
temporal constraints with both preferences and uncertainty can be defined. We
show how three classical notions of controllability (that is, strong, weak, and
dynamic), which have been developed for uncertain temporal problems, can be
generalized to handle preferences as well. After defining this general
framework, we focus on problems where preferences follow the fuzzy approach,
and with properties that assure tractability. For such problems, we propose
algorithms to check the presence of the controllability properties. In
particular, we show that in such a setting dealing simultaneously with
preferences and uncertainty does not increase the complexity of controllability
testing. We also develop a dynamic execution algorithm, of polynomial
complexity, that produces temporal plans under uncertainty that are optimal
with respect to fuzzy preferences
Building valoristaion strategies for biodiverse products - the approach
The market valorisation of âdiverse food productsâ is crucial to increase diversity in farming systems. It involves multiple actors, from the field to the table, and requires an integrated approach to take into account several dimensions involved
Building Valorisation Strategies for Biodiverse Products - Case Studies
The market valorisation of âdiverse food productsâ is crucial to promote agrobiodiversity. Despite the differences due to the specific contexts, valorisation strategies show relevant common features
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