5,739 research outputs found
Design analysis of ductile failure in dovetail connections
The static plastic collapse of ductile dovetail structures is investigated by three analysis methods: slip-line field (SLF) theory based on a sheet drawing model, finite element limit analysis, and linear elastic finite element analysis with adapted pressure vessel design stress linearization and categorization methods. A range of angles and heights are considered in the investigation. Three experimental test cases are also presented. The limit analysis results are found to give the best comparison with the limited experimental results, indicating similar collapse loads and modes of ductile collapse. The SLF solution is found to give conservative but useful failure loads for small dovetail angles but, at angles greater than 30°, the solution is not generally conservative. The pressure vessel design by the analysis stress categorization procedure was adapted for dovetail analysis and was found to give reasonably conservative collapse loads in most cases. However, the procedure requires the designer to consider a number of different stress classification lines to ensure that a conservative collapse load is identified. It is concluded that the finite element limit analysis approach provides the best and most direct route to calculating the allowable load for the joint and is the preferred method when appropriate finite element analysis facilities are available
Magnetic and superconducting properties on S-type single-crystal CeCuSi probed by Cu nuclear magnetic resonance and nuclear quadrupole resonance
We have performed Cu nuclear magnetic resonance/nuclear quadrupole
resonance measurements to investigate the magnetic and superconducting (SC)
properties on a "superconductivity dominant" (-type) single crystal of
CeCuSi. Although the development of antiferromagnetic (AFM)
fluctuations down to 1~K indicated that the AFM criticality was close, Korringa
behavior was observed below 0.8~K, and no magnetic anomaly was observed above
0.6 K. These behaviors were expected in -type
CeCuSi. The temperature dependence of the nuclear spin-lattice
relaxation rate at zero field was almost identical to that in the
previous polycrystalline samples down to 130~mK, but the temperature dependence
deviated downward below 120~mK. In fact, in the SC state could be
fitted with the two-gap -wave rather than the two-gap -wave
model down to 90~mK. Under magnetic fields, the spin susceptibility in both
directions clearly decreased below , indicative of the formation of
spin singlet pairing. The residual part of the spin susceptibility was
understood by the field-induced residual density of states evaluated from
, which was ascribed to the effect of the vortex cores. No magnetic
anomaly was observed above the upper critical field , but the
development of AFM fluctuations was observed, indicating that superconductivity
was realized in strong AFM fluctuations.Comment: 10 pages, 8 figure
Preparing for disaster: a comparative analysis of education for critical infrastructure collapse
This article explores policy approaches to educating populations for potential critical infrastructure collapse in five different countries: the UK, the US, Germany, Japan and New Zealand. ‘Critical infrastructure’ is not always easy to define, and indeed is defined slightly differently across countries – it includes entities vital to life, such as utilities (water, energy), transportation systems and communications, and may also include social and cultural infrastructure. The article is a mapping exercise of different approaches to critical infrastructure protection and preparedness education by the five countries. The exercise facilitates a comparison of the countries and enables us to identify distinctive characteristics of each country’s approach. We argue that contrary to what most scholars of security have argued, these national approaches diverge greatly, suggesting that they are shaped more by internal politics and culture than by global approaches
Magnetotransport in Sr3PbO antiperovskite with three-dimensional massive Dirac electrons
Novel topological phenomena are anticipated for three-dimensional (3D) Dirac
electrons. The magnetotransport properties of cubic
antiperovskite, theoretically proposed to be a 3D massive Dirac electron
system, are studied. The measurements of Shubnikov-de Haas oscillations and
Hall resistivity indicate the presence of a low density ( ) of holes with an extremely small cyclotron mass of
0.01-0.06. The magnetoresistance is linear in
magnetic field with the magnitude independent of temperature. These results
are fully consistent with the presence of 3D massive Dirac electrons in . The chemical flexibility of the antiperovskites and our findings
in the family member, , point to their potential as a model
system in which to explore exotic topological phases
A Novel Generic Framework for Track Fitting in Complex Detector Systems
This paper presents a novel framework for track fitting which is usable in a
wide range of experiments, independent of the specific event topology, detector
setup, or magnetic field arrangement. This goal is achieved through a
completely modular design. Fitting algorithms are implemented as
interchangeable modules. At present, the framework contains a validated Kalman
filter. Track parameterizations and the routines required to extrapolate the
track parameters and their covariance matrices through the experiment are also
implemented as interchangeable modules. Different track parameterizations and
extrapolation routines can be used simultaneously for fitting of the same
physical track. Representations of detector hits are the third modular
ingredient to the framework. The hit dimensionality and orientation of planar
tracking detectors are not restricted. Tracking information from detectors
which do not measure the passage of particles in a fixed physical detector
plane, e.g. drift chambers or TPCs, is used without any simplifications. The
concept is implemented in a light-weight C++ library called GENFIT, which is
available as free software
Signatures of the superfluid to Mott insulator transition in equilibrium and in dynamical ramps
We investigate the equilibrium and dynamical properties of the Bose-Hubbard
model and the related particle-hole symmetric spin-1 model in the vicinity of
the superfluid to Mott insulator quantum phase transition. We employ the
following methods: exact-diagonalization, mean field (Gutzwiller), cluster
mean-field, and mean-field plus Gaussian fluctuations. In the first part of the
paper we benchmark the four methods by analyzing the equilibrium problem and
give numerical estimates for observables such as the density of double
occupancies and their correlation function. In the second part, we study
parametric ramps from the superfluid to the Mott insulator and map out the
crossover from the regime of fast ramps, which is dominated by local physics,
to the regime of slow ramps with a characteristic universal power law scaling,
which is dominated by long wavelength excitations. We calculate values of
several relevant physical observables, characteristic time scales, and an
optimal protocol needed for observing universal scaling.Comment: 23 pages, 13 figure
Pressure-induced phase transitions of halogen-bridged binuclear metal complexes R_4[Pt_2(P_2O_5H_2)_4X]nH_2O
Recent contrasting observations for halogen (X)-bridged binuclear platinum
complexes R_4[Pt_2(P_2O_5H_2)_4X]nH_2O, that is, pressure-induced Peierls and
reverse Peierls instabilities, are explained by finite-temperature Hartree-Fock
calculations. It is demonstrated that increasing pressure transforms the
initial charge-polarization state into a charge-density-wave state at high
temperatures, whereas the charge-density-wave state oppositely declines with
increasing pressure at low temperatures. We further predict that
higher-pressure experiments should reveal successive phase transitions around
room temperature.Comment: 5 pages, 4 figures embedded, to be published in Phys. Rev. B 64,
September 1 (2001) Rapid Commu
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