4,172 research outputs found
PSYCHO-PEDAGOGICAL EXPERIMENT TO TEST TOOLS OF THE DEVELOPMENT OF PROFESSIONAL PSYCHOLOGICAL FITNESS FUTURE OFFICERS INTERIOR TROOPS
В статье представляются результаты психолого-педагогического эксперимента по проверке инструментария развития профессиональной психологической пригодности будущих офицеров внутренних войск. Авторы обосновывают актуальность проведения такой работы, рассматривают каждый полученный результат, уровень и показатель, и обозначают, что они решают в комплексе. На основе представленных данных сделаны соответствующие выводы по использованию результатов в образовательной практике военного вуза.The article presents the results of psycho-pedagogical experiment verification tools of professional psychological suitability of the future officers of the internal troops. The authors substantiate the relevance of this work, considering each result, the level and rate, and indicate that they decide in the complex. On the basis of data made conclusions on the use of results in educational practice of military high school
Determination of Bi in complex oxide samples by atomic absorption spectrometry by using ordinary acetylene – air flame atomization
In the present work the air/acetylene flame atomic absorption spectrometry was used for bismuth determination in complex oxides. Interference studies were carried out, and interference with vanadium and molybdenum was detected. The method of standard additions and traditional calibration curve method were used. Calibration and standard addition curves were fitted with linear and polynomial functions. It was shown that using polynomial function gives better results for the standard additions method for determination of bismuth by acetylene/air flame atomic absorption spectrometry. The calibration curve method was shown to be correct at low ( 10mg/L) concentration of an interferent
From Form Factors to Correlation Functions: The Ising Model
Using exact expressions for the Ising form factors, we give a new very simple
proof that the spin-spin and disorder-disorder correlation functions are
governed by the Painlev\'e III non linear differential equation. We also show
that the generating function of the correlation functions of the descendents of
the spin and disorder operators is a -soliton, , -function
of the sinh-Gordon hierarchy. We discuss a relation of our approach to
isomonodromy deformation problems, as well as further possible generalizations.Comment: SPhT-92-062; LPTHE-92-2
On Symmetries of Some Massless 2D Field Theories
We describe few aspects of the quantum symmetries of some massless
two-dimensional field theories. We discuss their relations with recent
proposals for the factorized scattering theories of the massless and
sigma models. We use these symmetries to propose massless
factorized S-matrices for the sigma models with topological terms at
any level, alias the models, and for the -coset massless flows.Comment: 13 page
Differential Equations for Sine-Gordon Correlation Functions at the Free Fermion Point
We demonstrate that for the sine-Gordon theory at the free fermion point, the
2-point correlation functions of the fields \exp (i\al \Phi ) for 0< \al <
1 can be parameterized in terms of a solution to a sinh-Gordon-like equation.
This result is derived by summing over intermediate multiparticle states and
using the form factors to express this as a Fredholm determinant. The proof of
the differential equations relies on a \Zmath_2 graded multiplication law
satisfied by the integral operators of the Fredholm determinant. Using this
methodology, we give a new proof of the differential equations which govern the
spin and disorder field correlators in the Ising model.Comment: 28 pages. In this corrected version, more general solutions to the
differential equations, which are required for correlators of inequivalent
fields, are included. erratum hep-th/9703055 describes the substantial
changes from original versio
Energy localization in carbon nanotubes
In this paper, the energy localization phenomena in low-frequency nonlinear oscillations of single-walled carbon nanotubes (SWNTs) are analysed. The SWNTs dynamics is studied in the framework of the Sanders-Koiter shell theory. Simply supported and free boundary conditions are considered. The effect of the aspect ratio on the analytical and numerical values of the localization threshold is investigated in nonlinear field
Nonlinear vibrations and energy distribution of carbon nanotubes
The nonlinear vibrations of Single-Walled Carbon Nanotubes are analysed. The Sanders-Koiter elastic shell theory is applied in order to obtain the elastic strain energy and kinetic energy. The carbon nanotube deformation is described in terms of longitudinal, circumferential and radial displacement fields. The theory considers geometric nonlinearities due to large amplitude of vibration. The displacement fields are expanded by means of a double series based on harmonic functions for the circumferential variable and Chebyshev polynomials for the longitudinal variable. The Rayleigh-Ritz method is applied to obtain approximate natural frequencies and mode shapes. Free boundary conditions are considered. In the nonlinear analysis, the three displacement fields are re-expanded by using approximate eigenfunctions. An energy approach based on the Lagrange equations is considered in order to obtain a set of nonlinear ordinary differential equations. The total energy distribution of the shell is studied by considering combinations of different vibration modes. The effect of the conjugate modes participation is analysed
Eigenfrequencies and vibration modes of carbon nanotubes
In 1991 Iijima discovered Carbon Nanotubes, he synthesised molecular carbon structures in the form of fullerenes and then reported the preparation of a new type of finite carbon structure consisting of needle-like tubes, the carbon nanotubes, described as helical microtubules of graphitic carbon.
Examples of applications of Carbon Nanotubes (CNTs) can be found in ultrahigh frequency nanomechanical resonators, in a large number of nanoelectromechanical devices such as sensors, oscillators, charge detectors and field emission devices. The reduction of the size and the increment of the stiffness of a resonator magnify its resonant frequencies and reduce its energy consumption, improving its sensitivity.
The modal analysis of carbon nanotubes is important because it allows to obtain the resonant frequencies and mode shapes, which influence the mechanical and electronic properties of the nanotube resonators.
A large number of experiments and atomistic simulations were conducted both on single-walled (SWNTs) and multi-walled carbon nanotubes (MWNTs).
The present work is concerned with the analysis of low-frequency linear vibrations of SWNTs: two approaches are presented: a fully analytical method based on a simplified theory and a semi-analytical method based on the theory of thin walled shells.
The semi-analytical approach (shortly called “numerical approach”) is based on the Sanders-Koiter shell theory and the Rayleigh-Ritz numerical procedure. The nanotube deformation is described in terms of longitudinal, circumferential and radial displacement fields, which are expanded by means of a double mixed series based on Chebyshev polynomials for the longitudinal variable and harmonic functions for the circumferential variable. The Rayleigh-Ritz method is then applied to obtain numerically approximate natural frequencies and mode shapes.
The second approach is based on a reduced version of the Sanders-Koiter shell theory, obtained by assuming small ring and tangential shear deformations. These assumptions allow to condense both the longitudinal and the circumferential displacement fields. A fourth-order partial differential equation for the radial displacement field is derived. Eigenfunctions are formally obtained analytically, then the numerical solution of the dispersion equation gives the natural frequencies and the corresponding normal modes.
The methods are fully validated by comparing the natural frequencies of the SWNTs with data available in literature, namely: experiments, molecular dynamics simulations and finite element analyses. A comparison between the results of the numerical and analytical approach is carried out in order to check the accuracy of the last one.
It is worthwhile to stress that the analytical model allows to obtain results with very low computational effort. On the other hand the numerical approach is able to handle the most realistic boundary conditions of SWNTs (free-free, clamped-free) with extreme accuracy. Both methods are suitable for a forthcoming extension to multi-walled nanotubes and nonlinear vibrations
The Quantum Double in Integrable Quantum Field Theory
Various aspects of recent works on affine quantum group symmetry of
integrable 2d quantum field theory are reviewed and further clarified. A
geometrical meaning is given to the quantum double, and other properties of
quantum groups. Multiplicative presentations of the Yangian double are
analyzed.Comment: 43 page
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