322 research outputs found
Influence of carbon on spin reorientation processes in Er 2-xRxFe14C (R = Gd, Pr) - Mossbauer and magnetometric studies
The Er2¡xRxFe14C (R=Gd, Pr) polycrystalline compounds have been synthesized and investigated with
57Fe Mössbauer spectroscopy and magnetic measurements. The spin reorientation phenomena were studied
extensively by narrow step temperature scanning in the neighborhood of the spin reorientation temperature.
Obtained Mössbauer spectra were analyzed using a procedure of simultaneous fitting and the transmission integral approach. Consistent description of Mössbauer spectra were obtained, temperature and composition dependencies of hyperfine interaction parameters and subspectra contributions were derived from fits and the transition temperatures were determined for all the compounds studied. Initial magnetization versus temperature measurements (in zero and non-zero external field) for Er2¡xGdxFe14C compounds allowed to establish the temperature regions of reorientation, change of magnetization value during the transition process. The results obtained with different methods were analyzed and the spin arrangement diagrams were constructed. Data obtained for Er2¡xGdxFe14C were compared with those for Er2¡xGdxFe14B series
Analysis of filtration processes in small experimental embankment based on numerical modeling and temperature measurements
Abstract This paper presents analysis of filtration processes in small experimental embankment. The analysis is based on field measurements and numerical modeling. The measurements were performed on experimental embankment, which size is in scale 1:5 comparing to typical river embankments in Poland. The measurements are made during flooding experiment. Two parameters during experiment ware measured: pore pressure and temperature. Additionally, the thermograpical observation of air side of embankment was conducted. The FLAC 7.0 software was used in 2D numerical modeling. Modification the parameters of the model allowed to fit the modelled data to the measured data
Evolving Spatially Aggregated Features from Satellite Imagery for Regional Modeling
Satellite imagery and remote sensing provide explanatory variables at
relatively high resolutions for modeling geospatial phenomena, yet regional
summaries are often desirable for analysis and actionable insight. In this
paper, we propose a novel method of inducing spatial aggregations as a
component of the machine learning process, yielding regional model features
whose construction is driven by model prediction performance rather than prior
assumptions. Our results demonstrate that Genetic Programming is particularly
well suited to this type of feature construction because it can automatically
synthesize appropriate aggregations, as well as better incorporate them into
predictive models compared to other regression methods we tested. In our
experiments we consider a specific problem instance and real-world dataset
relevant to predicting snow properties in high-mountain Asia
Phantom cosmology as a scattering process
We study the general chaotic features of dynamics of the phantom field
modelled in terms of a single scalar field conformally coupled to gravity. We
demonstrate that the dynamics of the FRW model with dark energy in the form of
phantom field can be regarded as a scattering process of two types: multiple
chaotic and classical non-chaotic. It depends whether the spontaneously
symmetry breaking takes place. In the first class of models with the
spontaneously symmetry breaking the dynamics is similar to the Yang-Mills
theory. We find the evidence of a fractal structure in the phase space of
initial conditions. We observe similarities to the phenomenon of a multiple
scattering process around the origin. In turn the class of models without the
spontaneously symmetry breaking can be described as the classical non-chaotic
scattering process and the methods of symbolic dynamic are also used in this
case. We show that the phantom cosmology can be treated as a simple model with
scattering of trajectories which character depends crucially on a sign of a
square of mass. We demonstrate that there is a possibility of chaotic behavior
in the flat Universe with a conformally coupled phantom field in the system
considered on non-zero energy level. We obtain that the acceleration is a
generic feature in the considered model without the spontaneously symmetry
breaking. We observe that the effective EOS coefficient oscillates and then
approach to .Comment: RevTeX4, 19 pages, 17 figures; v2 - added a comment on the Yang-Mills
cosmological models and bibliography; v3 - added a section on acceleration, 2
figures, some references
Microscopic derivation of Ginzburg-Landau equations for coexistent states of superconductivity and magnetism
Ginzburg-Landau (GL) equations for the coexistent states of superconductivity
and magnetism are derived microscopically from the extended Hubbard model with
on-site repulsive and nearest-neighbor attractive interactions. In the derived
GL free energy a cubic term that couples the spin-singlet and spin-triplet
components of superconducting order parameters (SCOP) with magnetization
exists. This term gives rise to a spin-triplet SCOP near the interface between
a spin-singlet superconductor and a ferromagnet, consistent with previous
theoretical studies based on the Bogoliubov de Gennes method and the
quasiclassical Green's function theory. In coexistent states of singlet
superconductivity and antiferromagnetism it leads to the occurrence of
pi-triplet SCOPs.Comment: 18 page
Classical big-bounce cosmology: dynamical analysis of a homogeneous and irrotational Weyssenhoff fluid
A dynamical analysis of an effective homogeneous and irrotational Weyssenhoff
fluid in general relativity is performed using the 1+3 covariant approach that
enables the dynamics of the fluid to be determined without assuming any
particular form for the space-time metric. The spin contributions to the field
equations produce a bounce that averts an initial singularity, provided that
the spin density exceeds the rate of shear. At later times, when the spin
contribution can be neglected, a Weyssenhoff fluid reduces to a standard
cosmological fluid in general relativity. Numerical solutions for the time
evolution of the generalised scale factor in spatially-curved models are
presented, some of which exhibit eternal oscillatory behaviour without any
singularities. In spatially-flat models, analytical solutions for particular
values of the equation-of-state parameter are derived. Although the scale
factor of a Weyssenhoff fluid generically has a positive temporal curvature
near a bounce, it requires unreasonable fine tuning of the equation-of-state
parameter to produce a sufficiently extended period of inflation to fit the
current observational data.Comment: 34 pages, 18 figure
Electron transport through strongly interacting quantum dot coupled to normal metal and superconductor
We study the electron transport through the quantum dot coupled to the normal
metal and BCS-like superconductor (N - QD - S) in the presence of the Kondo
effect and Andreev scattering. The system is described by the single impurity
Anderson model in the limit of strong on-dot interaction. We use recently
proposed equation of motion technique for Keldysh nonequilibrium Green's
function together with the modified slave boson approach to study the electron
transport. We derive formula for the current which contains various tunneling
processes and apply it to study the transport through the system. We find that
the Andreev conductance is strongly suppressed and there is no zero-bias
(Kondo) anomaly in the differential conductance. We discuss effects of the
particle-hole asymmetry in the electrodes as well as the asymmetry in the
couplings.Comment: Supercond. Sci. Technol. - accepted for publicatio
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Dialectic tensions in the financial markets: a longitudinal study of pre- and post-crisis regulatory technology
This article presents the findings from a longitudinal research study on regulatory technology in the UK financial services industry. The financial crisis with serious corporate and mutual fund scandals raised the profile of
compliance as governmental bodies, institutional and private investors introduced a ‘tsunami’ of financial regulations. Adopting a multi-level analysis, this study examines how regulatory technology was used by financial firms to meet their compliance obligations, pre- and post-crisis. Empirical data collected over 12 years examine the deployment of
an investment management system in eight financial firms. Interviews with public regulatory bodies, financial
institutions and technology providers reveal a culture of compliance with increased transparency, surveillance and
accountability. Findings show that dialectic tensions arise as the pursuit of transparency, surveillance and
accountability in compliance mandates is simultaneously rationalized, facilitated and obscured by regulatory
technology. Responding to these challenges, regulatory bodies continue to impose revised compliance mandates on
financial firms to force them to adapt their financial technologies in an ever-changing multi-jurisdictional regulatory landscape
Non-equilibrium Kondo effect in asymmetrically coupled quantum dot
The quantum dot asymmetrically coupled to the external leads has been
analysed theoretically by means of the equation of motion (EOM) technique and
the non-crossing approximation (NCA). The system has been described by the
single impurity Anderson model. To calculate the conductance across the device
the non-equilibrium Green's function technique has been used. The obtained
results show the importance of the asymmetry of the coupling for the appearance
of the Kondo peak at nonzero voltages and qualitatively explain recent
experiments.Comment: 7 pages, 6 figures, Physical Review B (accepted for publication
Numerical Renormalization Group Approach to a Quantum Dot Coupled to Normal and Superconducting Leads
We study transport through a quantum dot coupled to normal and
superconducting leads using the numerical renormalization group method. We show
that the low-energy properties of the system are described by the local Fermi
liquid theory despite of the superconducting correlations penetrated into the
dot due to a proximity effect. We calculate the linear conductance due to the
Andreev reflection in the presence of the Coulomb interaction. It is
demonstrated that the maximum structure appearing in the conductance clearly
characterizes a crossover between two distinct spin-singlet ground states, i.e.
the superconducting singlet state and the Kondo singlet state. It is further
elucidated that the gate-voltage dependence of the conductance shows different
behavior in the superconducting singlet region from that in the Kondo singlet
region.Comment: 10 pages, 6 figures; a typo in eq. (B.5) corrected, which does not
affect any other results of the pape
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