1,427 research outputs found
Bending resistance of austenitic stainless steel hollow sections at elevated temperatures
The present research aims to increase the knowledge of the structural behaviour of stainless steel members under
fire. Eight experimental bending tests at elevated temperatures (500, 700 ÂșC) built with RHS 150Ă100Ă3
austenitic stainless-steel beams, using two different grades (1.4301, 1.4571) also known as 304 and 316Ti, are
presented. Both grades 1.4301 (X5CrNi18â10) and 1.4571 (X6CrNiMo17â12â2) have almost the same core
chemical composition but there are some differences, especially the grade 1.4571 has 2â2.5% molybdenum and a
small amount of titanium (less than 0.7%). Grade 1.4301 presents good rust resistance, sufficient acid resistance
and good weldability, while grade 1.4571 presents very good rust resistance, very good acid resistance and also
good weldability. Both have almost the same strength, but grade 1.4571 has superior strength at elevated
temperatures. Both material grades were experimentally characterised with coupon tensile tests at room temperature.
The load-displacement behaviour is validated with 3D shell finite element models, assuming a true
stress-strain material model, based on the two-stage Ramberg Osgood constitutive law. With the developed
numerical model, a parametric analysis is presented to study the fire resistance of beams from both materials,
using three different cross-sections and eleven different temperatures. The bending resistance obtained with the
finite element model is in good agreement with the cross-sectional design moment resistance, when considering
the effective area, confirming that the design rules from EN1993â1â2 are safe for less slender cross-sections and
unsafe for the most slender cross-sections.info:eu-repo/semantics/publishedVersio
The Stress-Energy Tensor in Soluble Models of Spherically Symmetric Charged Black Hole Evaporation
We study the decay of a near-extremal black hole in AdS, related to the
near-horizon region of 3+1-dimensional Reissner-Nordstr\"om spacetime,
following Fabbri, Navarro, and Navarro-Salas. Back-reaction is included in a
semiclassical approximation. Calculations of the stress-energy tensor of matter
coupled to the physical spacetime for an affine null observer demonstrate that
the black hole evaporation proceeds smoothly and the near-extremal black hole
evolves back to an extremal ground state, until this approximation breaks down.Comment: 19 pages, 14 figure
An overview of the current status of CMB observations
In this paper we briefly review the current status of the Cosmic Microwave
Background (CMB) observations, summarising the latest results obtained from CMB
experiments, both in intensity and polarization, and the constraints imposed on
the cosmological parameters. We also present a summary of current and future
CMB experiments, with a special focus on the quest for the CMB B-mode
polarization.Comment: Latest CMB results have been included. References added. To appear in
"Highlights of Spanish Astrophysics V", Proceedings of the VIII Scientific
Meeting of the Spanish Astronomical Society (SEA) held in Santander, 7-11
July, 200
Discrete molecular dynamics simulations of peptide aggregation
We study the aggregation of peptides using the discrete molecular dynamics
simulations. At temperatures above the alpha-helix melting temperature of a
single peptide, the model peptides aggregate into a multi-layer parallel
beta-sheet structure. This structure has an inter-strand distance of 0.48 nm
and an inter-sheet distance of 1.0 nm, which agree with experimental
observations. In this model, the hydrogen bond interactions give rise to the
inter-strand spacing in beta-sheets, while the Go interactions among side
chains make beta-strands parallel to each other and allow beta-sheets to pack
into layers. The aggregates also contain free edges which may allow for further
aggregation of model peptides to form elongated fibrils.Comment: 15 pages, 8 figure
Quantum dilaton gravity as a linear dilaton conformal field theory
A model of matter-coupled gravity in two dimensions is quantized. The crucial
requirement for performing the quantization is the vanishing of the conformal
anomaly, which is achieved by tuning a parameter in the interaction potential.
The spectrum of the theory is determined by mapping the model first onto a
field theory with a Liouville interaction, then onto a linear dilaton conformal
field theory. In absence of matter fields a pure gauge theory with massless
ground state is found; otherwise it is possible to minimally couple up to 11
matter scalar fields: in this case the ground state is tachyonic and the matter
sector decouples, like the transverse oscillators in the critical bosonic
string.Comment: 7 pages, RevTeX4 file. v2: some comments and one reference adde
Critical properties of superconducting Ba1-xKxFe2As2
Magnetisation and magnetoresistance measurements have been carried out on
superconducting Ba1-xKxFe2As2 samples with x=0.40 and 0.50. From low field
magnetization data carried out at different temperatures below TC, HC1 has been
extracted. The plot of HC1 versus temperature shows an anomalous increase at
low temperatures. From high field magnetization hysterisis measurements carried
out in fields up to 16 T at 4.2 K and 20 K, the critical current density has
been evaluated using the Bean critical state model. The JC determined from the
high field data is >104A/cm2 at 4.2 K and 5 T. The superconducting transitions
were also measured resistively in increasing applied magnetic fields up to 12
Tesla. From the variation of the TC onset with applied field, dHC2/dT at TC was
obtained to be -7.708 T/K and -5.57 T/K in the samples with x=0.40 and 0.50.Comment: 14 pages; 7 figure
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