3,122 research outputs found
Propagation of Exchange Bias in CoFe/FeMn/CoFe Trilayers
CoFe/FeMn, FeMn/CoFe bilayers and CoFe/FeMn/CoFe trilayers were grown in
magnetic field and at room temperature. The exchange bias field
depends strongly on the order of depositions and is much higher at CoFe/FeMn
than at FeMn/CoFe interfaces. By combining the two bilayer structures into
symmetric CoFe/FeMn()/CoFe trilayers, and
of the top and bottom CoFe layers, respectively, are both enhanced.
Reducing of the trilayers also results in enhancements of
both and . These results evidence the propagation of
exchange bias between the two CoFe/FeMn and FeMn/CoFe interfaces mediated by
the FeMn antiferromagnetic order
Automatic analysis of Pole Mounted Auto-Recloser data for fault diagnosis and prognosis
Fault diagnosis is a key part of a control and protection engineer’s role to ensure the effective and stable performance of electrical power networks. One challenge is to support the analysis and application of expert judgement to the, often, large data sets generated. To assist engineers with this task and improve network reliability, this research focuses on analysing previous fault activity in order to obtain an early-warning report to assist fault diagnosis and fault prognosis. This paper details the design of an integrated system with a fault diagnosis algorithm utilising available Supervisory Control And Data Acquisition (SCADA) alarm data and 11kV distribution network data captured from Pole Mounted Auto-Reclosers (PMARs) (provided by a leading UK network operator). The developed system will be capable of diagnosing the nature of a circuit’s previous fault activity, underlying circuit activity and evolving fault activity and the risk of future fault activity. This will provide prognostic decision support for network operators and maintenance staff
The intermittent behavior and hierarchical clustering of the cosmic mass field
The hierarchical clustering model of the cosmic mass field is examined in the
context of intermittency. We show that the mass field satisfying the
correlation hierarchy is intermittent if , where is the dimension of the field, and is the power-law
index of the non-linear power spectrum in the discrete wavelet transform (DWT)
representation. We also find that a field with singular clustering can be
described by hierarchical clustering models with scale-dependent coefficients
and that this scale-dependence is completely determined by the
intermittent exponent and . Moreover, the singular exponents of a field
can be calculated by the asymptotic behavior of when is large.
Applying this result to the transmitted flux of HS1700 Ly forests, we
find that the underlying mass field of the Ly forests is significantly
intermittent. On physical scales less than about 2.0 h Mpc, the observed
intermittent behavior is qualitatively different from the prediction of the
hierarchical clustering with constant . The observations, however, do show
the existence of an asymptotic value for the singular exponents. Therefore, the
mass field can be described by the hierarchical clustering model with
scale-dependent . The singular exponent indicates that the cosmic mass
field at redshift is weakly singular at least on physical scales as
small as 10 h kpc.Comment: AAS Latex file, 33 pages,5 figures included, accepted for publication
in Ap
Quantum-electrodynamical treatment of second-harmonic generation through phase-conjugate six-wave mixing: Temporal analysis
Aspect sensitivity measurements of polar mesosphere summer echoes using coherent radar imaging
International audienceThe Esrange VHF radar (ESRAD), located in northern Sweden (67.88° N, 21.10° E), has been used to investigate polar mesosphere summer echoes (PMSE). During July and August of 1998, coherent radar imaging (CRI) was used to study the dynamic evolution of PMSE with high temporal and spatial resolution. A CRI analysis provides an estimate of the angular brightness distribution within the radar's probing volume. The brightness distribution is directly related to the radar reflectivity. Consequently, these data are used to investigate the aspect sensitivity of PMSE. In addition to the CRI analysis, the full correlation analysis (FCA) is used to derive estimates of the prevailing three-dimensional wind associated with the observed PMSE. It is shown that regions within the PMSE with enhanced aspect sensitivity have a correspondingly high signal-to-noise ratio (SNR). Although this relationship has been investigated in the past, the present study allows for an estimation of the aspect sensitivity independent of the assumed scattering models and avoids the complications of comparing echo strengths from vertical and off-vertical beams over large horizontal separations, as in the Doppler Beam Swinging (DBS) method. Regions of enhanced aspect sensitivity were additionally shown to correlate with the wave-perturbation induced downward motions of air parcels embedded in the PMSE
Enteral Nutrition in Crohn’s Disease: An Underused Therapy
This paper reviews the literature on the history, efficacy, and putative mechanism of action of enteral nutrition for inflammatory bowel disease in both paediatric and adult patients. It also analyses the reasoning behind the low popularity of exclusive enteral nutrition in clinical practice despite the benefits and safety profile
Time evolution of correlation functions and thermalization
We investigate the time evolution of a classical ensemble of isolated
periodic chains of O(N)-symmetric anharmonic oscillators. Our method is based
on an exact evolution equation for the time dependence of correlation
functions. We discuss its solutions in an approximation which retains all
contributions in next-to-leading order in a 1/N expansion and preserves time
reflection symmetry. We observe effective irreversibility and approximate
thermalization. At large time the system approaches stationary solutions in the
vicinity of, but not identical to, thermal equilibrium. The ensemble therefore
retains some memory of the initial condition beyond the conserved total energy.
Such a behavior with incomplete thermalization is referred to as "mesoscopic
dynamics". It is expected for systems in a small volume. Surprisingly, we find
that the nonthermal asymptotic stationary solutions do not change for large
volume. This raises questions on Boltzmann's conjecture that macroscopic
isolated systems thermalize.Comment: 40 pages, 9 figure
Long-range forces between two excited mercury atoms and associative ionization
The long-range quadrupole-quadrupole () and leading dispersion
() interactions between all pairs of excited Hg() ,
, , and atoms are determined. The quadrupole moments are
calculated using the {\it ab initio} relativistic configuration-interaction
method coupled with many-body perturbation theory. The van der Waals
coefficients are approximated using previously calculated static
polarizabilities and expressions for the dispersion energy that are validated
with similar systems. The long-range interactions are critical for associative
ionization in thermal and cold collisions, and are found to be quite different
for different pairs of interacting states. Based on this knowledge and the
short-range parts of previously calculated potential curves, improved estimates
of the chemi-ionization cross sections are obtained.Comment: accepted in Phys Rev
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