59 research outputs found
Thermodynamic and dynamic dielectric properties of one-dimensional hydrogen bonded ferroelectric of PbHPO-type
Within the modified model of proton ordering of one-dimensional ferroelectric
having hydrogen bonds of PbHPO-type, their thermodynamic and dynamic
characteristics are studied and calculated taking into account the linear (by
crystal deformations () and )
contributions into the energy of a proton system but without taking into
account the tunneling in the two-particle cluster approximation. There has been
obtained a good quantitative description of the temperature dependence of
polarization, static dielectric permittivity, heat capacity and frequency
dependence of dynamic dielectric permittivity at different temperatures for
PbHPO and PbHDO crystals.Comment: 12 pages, 7 figure
Statistical theory of thermodynamic and dynamic properties of the RbHSO ferroelectrics
Within the modified four-sublattice model of RbHSO with taking into
account the piezoelectric coupling to the strains ,
, , and , the polarization
components, static and dynamic dielectric permittivity of clamped and free
crystal are calculated in the mean field approximation. At the proper choice of
the values of the theory parameters, a satisfactory quantitative description of
the available experimental data is obtained.Comment: 16 pages, 15 figure
On the Aizenman exponent in critical percolation
The probabilities of clusters spanning a hypercube of dimensions two to seven
along one axis of a percolation system under criticality were investigated
numerically. We used a modified Hoshen--Kopelman algorithm combined with
Grassberger's "go with the winner" strategy for the site percolation. We
carried out a finite-size analysis of the data and found that the probabilities
confirm Aizenman's proposal of the multiplicity exponent for dimensions three
to five. A crossover to the mean-field behavior around the upper critical
dimension is also discussed.Comment: 5 pages, 4 figures, 4 table
The RANLUX generator: resonances in a random walk test
Using a recently proposed directed random walk test, we systematically
investigate the popular random number generator RANLUX developed by Luescher
and implemented by James. We confirm the good quality of this generator with
the recommended luxury level. At a smaller luxury level (for instance equal to
1) resonances are observed in the random walk test. We also find that the
lagged Fibonacci and Subtract-with-Carry recipes exhibit similar failures in
the random walk test. A revised analysis of the corresponding dynamical systems
leads to the observation of resonances in the eigenvalues of Jacobi matrix.Comment: 18 pages with 14 figures, Essential addings in the Abstract onl
A study of logarithmic corrections and universal amplitude ratios in the two-dimensional 4-state Potts model
Monte Carlo (MC) and series expansion (SE) data for the energy, specific
heat, magnetization and susceptibility of the two-dimensional 4-state Potts
model in the vicinity of the critical point are analysed. The role of
logarithmic corrections is discussed and an approach is proposed in order to
account numerically for these corrections in the determination of critical
amplitudes. Accurate estimates of universal amplitude ratios ,
, and are given, which arouse
new questions with respect to previous works
The critical amplitude ratio of the susceptibility in the random-site two-dimensional Ising model
We present a new way of probing the universality class of the site-diluted
two-dimensional Ising model. We analyse Monte Carlo data for the magnetic
susceptibility, introducing a new fitting procedure in the critical region
applicable even for a single sample with quenched disorder. This gives us the
possibility to fit simultaneously the critical exponent, the critical amplitude
and the sample dependent pseudo-critical temperature. The critical amplitude
ratio of the magnetic susceptibility is seen to be independent of the
concentration of the empty sites for all investigated values of . At the same time the average effective exponent is found
to vary with the concentration , which may be argued to be due to
logarithmic corrections to the power law of the pure system. This corrections
are canceled in the susceptibility amplitude ratio as predicted by theory. The
central charge of the corresponding field theory was computed and compared well
with the theoretical predictions.Comment: 6 pages, 4 figure
The Number of Incipient Spanning Clusters in Two-Dimensional Percolation
Using methods of conformal field theory, we conjecture an exact form for the
probability that n distinct clusters span a large rectangle or open cylinder of
aspect ratio k, in the limit when k is large.Comment: 9 pages, LaTeX, 1 eps figure. Additional references and comparison
with existing numerical results include
Periodic orbits of the ensemble of Sinai-Arnold cat maps and pseudorandom number generation
We propose methods for constructing high-quality pseudorandom number
generators (RNGs) based on an ensemble of hyperbolic automorphisms of the unit
two-dimensional torus (Sinai-Arnold map or cat map) while keeping a part of the
information hidden. The single cat map provides the random properties expected
from a good RNG and is hence an appropriate building block for an RNG, although
unnecessary correlations are always present in practice. We show that
introducing hidden variables and introducing rotation in the RNG output,
accompanied with the proper initialization, dramatically suppress these
correlations. We analyze the mechanisms of the single-cat-map correlations
analytically and show how to diminish them. We generalize the Percival-Vivaldi
theory in the case of the ensemble of maps, find the period of the proposed RNG
analytically, and also analyze its properties. We present efficient practical
realizations for the RNGs and check our predictions numerically. We also test
our RNGs using the known stringent batteries of statistical tests and find that
the statistical properties of our best generators are not worse than those of
other best modern generators.Comment: 18 pages, 3 figures, 9 table
Motivation and stimulation mechanism of medical staff in developing countries: main challenges and ways of its improving in Ukraine
The main purpose of the article is to propose the effective instruments of motivation and stimulation of
the medical staff within the modern Healthcare Reform in Ukraine. In the article, the main problems and challenges
of the stimulation and motivation process of the medical personnel in Ukraine are viewed. The theoretical basis of
the motivation process is considered. This article analyses the approach of the differentiation of the “stimulation”
and “motivation” categories. The point is stressed that motivation’s main goal is a state change in the medical
organization from the point of view of personnel management, and the stimulation is directed to confirming this
state. So these two processes are the part of one strategic mechanism of the personnel management and should
complement each other. The current situation in the labour market of the healthcare sector is examined. The main
issues of this market are defined. And on the basis of the specified problems, the instruments and methods of
stimulation of medical staff are proposed by the author. The system of grids as the part of the financial and monetary
incentives at the medical establishment is offered with the purpose of its medical staff’s activity improvement.
The practical importance of the scientific research results lies in detailing the motivation and stimulation process and
its detailed analysis from the point of view of the healthcare sector, which is important for the further development
of the healthcare sphere in Ukraine. Methodology. The methodological basis of the article is the complex of methods,
including methods of scientific cognition, analysis and synthesis, systematization and scientific abstraction.
The informational basis of the conducted research is the scientific works of the domestic and foreign scientists in
the sphere of management and organization of health care, the statistical data of the State Statistics Service of
Ukraine, legal and regulatory documents of the Ministry of Health of Ukraine. Results. The proposed mechanism of
medical staff’s motivation and stimulation allows solving the problems related to the shortage of the medical staff,
the quality of their activity and their performance improvement etc. Further research directions are aimed at the
study of all aspects of managerial capital formation and improvement in the healthcare field
Critical properties of joint spin and Fortuin-Kasteleyn observables in the two-dimensional Potts model
The two-dimensional Potts model can be studied either in terms of the
original Q-component spins, or in the geometrical reformulation via
Fortuin-Kasteleyn (FK) clusters. While the FK representation makes sense for
arbitrary real values of Q by construction, it was only shown very recently
that the spin representation can be promoted to the same level of generality.
In this paper we show how to define the Potts model in terms of observables
that simultaneously keep track of the spin and FK degrees of freedom. This is
first done algebraically in terms of a transfer matrix that couples three
different representations of a partition algebra. Using this, one can study
correlation functions involving any given number of propagating spin clusters
with prescribed colours, each of which contains any given number of distinct FK
clusters. For 0 <= Q <= 4 the corresponding critical exponents are all of the
Kac form h_{r,s}, with integer indices r,s that we determine exactly both in
the bulk and in the boundary versions of the problem. In particular, we find
that the set of points where an FK cluster touches the hull of its surrounding
spin cluster has fractal dimension d_{2,1} = 2 - 2 h_{2,1}. If one constrains
this set to points where the neighbouring spin cluster extends to infinity, we
show that the dimension becomes d_{1,3} = 2 - 2 h_{1,3}. Our results are
supported by extensive transfer matrix and Monte Carlo computations.Comment: 15 pages, 3 figures, 2 table
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