236 research outputs found
Magnetization reversal process and nonlinear magneto-impedance in Cu/NiFe and Nb/NiFe composite wires
The magnetization reversal of Cu/NiFe and Nb/NiFe composite wires carrying AC
current is studied. The frequency spectrum of a voltage induced in a pick-up
coil wound around the wire is analyzed. The frequency spectrum is shown to
consist of even harmonics within a wide range of AC current amplitudes and
longitudinal DC magnetic fields. The strong dependencies of the harmonic
amplitudes on the DC field are found. The results obtained may be of importance
for the design of weak magnetic field sensors.Comment: 8 pages, 4 figures, publishe
Current distribution and giant magnetoimpedance in composite wires with helical magnetic anisotropy
The giant magnetoimpedance effect in composite wires consising of a
non-magnetic inner core and soft magnetic shell is studied theoretically. It is
assumed that the magnetic shell has a helical anisotropy. The current and field
distributions in the composite wire are found by means of a simultaneous
solution of Maxwell equations and the Landau-Lifshitz equation. The expressions
for the diagonal and off-diagonal impedance are obtained for low and high
frequencies. The dependences of the impedance on the anisotropy axis angle and
the shell thickness are analyzed. Maximum field sensitivity is shown to
correspond to the case of the circular anisotropy in the magnetic shell. It is
demonstrated that the optimum shell thickness to obtain maximum impedance ratio
is equal to the effective skin depth in the mahnetic material.Comment: 23 pages, 7 figure
Towards the String representation of the dual Abelian Higgs model beyond the London limit
We perform a path-integral analysis of the string representation of the dual
Abelian Higgs (DAH) model beyond the London limit, where the string describing
the vortex of a flux tube has a finite thickness. We show that besides an
additional vortex core contribution to the string tension, a modified Yukawa
interaction appears as a boundary contribution in the type-II dual
superconducting vacuum. In the London limit, the modified Yukawa interaction is
reduced to the Yukawa one.Comment: 13 pages, JHEP3.cls is used, no figures. The version accepted for
publication in JHE
Ensuring the seismic resistance of operated CHP buildings
The main structures of the engine room of the CHP are among the most responsible reinforced concrete structures, since during operation they are subjected to significant technological loads, including those not provided for by the project. One of the most significant impacts is seismic. During the long-term operation of the CHP, the building structures have experienced significant alternating loads. As a result, the thermal power plants built 45-60 years ago and currently in operation have a reduced level of seismic resistance. As recent events in Turkey have shown, ensuring the safe operation of power plants is a key task. However, new construction is expensive and not always justified, in this regard, the task is to ensure the seismic resistance of existing power plants in seismically hazardous areas
Anomalous scaling of a passive scalar in the presence of strong anisotropy
Field theoretic renormalization group and the operator product expansion are
applied to a model of a passive scalar field, advected by the Gaussian strongly
anisotropic velocity field. Inertial-range anomalous scaling behavior is
established, and explicit asymptotic expressions for the n-th order structure
functions of scalar field are obtained; they are represented by superpositions
of power laws with nonuniversal (dependent on the anisotropy parameters)
anomalous exponents. In the limit of vanishing anisotropy, the exponents are
associated with tensor composite operators built of the scalar gradients, and
exhibit a kind of hierarchy related to the degree of anisotropy: the less is
the rank, the less is the dimension and, consequently, the more important is
the contribution to the inertial-range behavior. The leading terms of the even
(odd) structure functions are given by the scalar (vector) operators. For the
finite anisotropy, the exponents cannot be associated with individual operators
(which are essentially ``mixed'' in renormalization), but the aforementioned
hierarchy survives for all the cases studied. The second-order structure
function is studied in more detail using the renormalization group and
zero-mode techniques.Comment: REVTEX file with EPS figure
Dynamical stability of infinite homogeneous self-gravitating systems: application of the Nyquist method
We complete classical investigations concerning the dynamical stability of an
infinite homogeneous gaseous medium described by the Euler-Poisson system or an
infinite homogeneous stellar system described by the Vlasov-Poisson system
(Jeans problem). To determine the stability of an infinite homogeneous stellar
system with respect to a perturbation of wavenumber k, we apply the Nyquist
method. We first consider the case of single-humped distributions and show
that, for infinite homogeneous systems, the onset of instability is the same in
a stellar system and in the corresponding barotropic gas, contrary to the case
of inhomogeneous systems. We show that this result is true for any symmetric
single-humped velocity distribution, not only for the Maxwellian. If we
specialize on isothermal and polytropic distributions, analytical expressions
for the growth rate, damping rate and pulsation period of the perturbation can
be given. Then, we consider the Vlasov stability of symmetric and asymmetric
double-humped distributions (two-stream stellar systems) and determine the
stability diagrams depending on the degree of asymmetry. We compare these
results with the Euler stability of two self-gravitating gaseous streams.
Finally, we determine the corresponding stability diagrams in the case of
plasmas and compare the results with self-gravitating systems
From Quasars to Extraordinary N-body Problems
We outline reasoning that led to the current theory of quasars and look at
George Contopoulos's place in the long history of the N-body problem. Following
Newton we find new exactly soluble N-body problems with multibody forces and
give a strange eternally pulsating system that in its other degrees of freedom
reaches statistical equilibrium.Comment: 13 pages, LaTeX with 1 postscript figure included. To appear in
Proceedings of New York Academy of Sciences, 13th Florida Workshop in
Nonlinear Astronomy and Physic
A blueprint for the synthesis and characterization of thiolated graphene
Graphene derivatization to either engineer its physical and chemical properties or overcome the problem of the facile synthesis of nanographenes is a subject of significant attention in the nanomaterials research community. In this paper, we propose a facile and scalable method for the synthesis of thiolated graphene via a two step liquid phase treatment of graphene oxide GO . Employing the core level methods, the introduction of up to 5.1 at. of thiols is indicated with the simultaneous rise of the C O ratio to 16.8. The crumpling of the graphene layer upon thiolation without its perforation is pointed out by microscopic and Raman studies. The conductance of thiolated graphene is revealed to be driven by the Mott hopping mechanism with the sheet resistance values of 2.15 k amp; 937; sq and dependable on the environment. The preliminary results on the chemiresistive effect of these films upon exposure to ethanol vapors in the mix with dry and humid air are shown. Finally, the work function value and valence band structure of thiolated graphene are analyzed. Taken together, the developed method and findings of the morphology and physics of the thiolated graphene guide the further application of this derivative in energy storage, sensing devices, and smart material
Transverse spin effects in hadron-pair production from semi-inclusive deep inelastic scattering
First measurements of azimuthal asymmetries in hadron-pair production in
deep-inelastic scattering of muons on transversely polarised ^6LiD (deuteron)
and NH_3 (proton) targets are presented. The data were taken in the years
2002-2004 and 2007 with the COMPASS spectrometer using a muon beam of 160 GeV/c
at the CERN SPS. The asymmetries provide access to the transversity
distribution functions, without involving the Collins effect as in single
hadron production. The sizeable asymmetries measured on the NH_ target indicate
non-vanishing u-quark transversity and two-hadron interference fragmentation
functions. The small asymmetries measured on the ^6LiD target can be
interpreted as indication for a cancellation of u- and d-quark transversities.Comment: 13 pages, 4 figures, updated to the published versio
Leading order determination of the gluon polarisation from DIS events with high-p_T hadron pairs
We present a determination of the gluon polarisation Delta g/g in the
nucleon, based on the longitudinal double-spin asymmetry of DIS events with a
pair of large transverse-momentum hadrons in the final state. The data were
obtained by the COMPASS experiment at CERN using a 160 GeV/c polarised muon
beam scattering off a polarised ^6LiD target. The gluon polarisation is
evaluated by a Neural Network approach for three intervals of the gluon
momentum fraction x_g covering the range 0.04 < x_g < 0.27. The values obtained
at leading order in QCD do not show any significant dependence on x_g. Their
average is Delta g/g = 0.125 +/- 0.060 (stat.) +/- 0.063 (syst.) at x_g=0.09
and a scale of mu^2 = 3 (GeV/c)^2.Comment: 13 pages, 6 figures and 3 table
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