166 research outputs found
Positive behavior in relation to human health
The positive attitude to health in behavior can be expressed both as in positive, and as in negative way, it conducts either to dynamic physical development of an organism, or to a large number of risk factors for healthПозитивное отношение к здоровью в поведении может выражаться как позитивно, так и негативно, это ведет либо к динамичному физическому развитию организма, либо к большому числу факторов риска для здоровь
Electronic structure of unidirectional superlattices in crossed electric and magnetic fields and related terahertz oscillations
We have studied Bloch electrons in a perfect unidirectional superlattice
subject to crossed electric and magnetic fields, where the magnetic field is
oriented ``in-plane'', i.e. in parallel to the sample plane. Two orientation of
the electric field are considered. It is shown that the magnetic field
suppresses the intersubband tunneling of the Zener type, but does not change
the frequency of Bloch oscillations, if the electric field is oriented
perpendicularly to both the sample plane and the magnetic field. The electric
field applied in-plane (but perpendicularly to the magnetic field) yields the
step-like electron energy spectrum, corresponding to the magnetic-field-tunable
oscillations alternative to the Bloch ones.Comment: 7 pages, 1 figure, accepted for publication in Phys. Rev.
LC nanocomposites: induced optical singularities, managed nano/micro structure, and electrical conductivity
Microstructure, phase transitions, electrical conductivity, and optical and
electrooptical properties of multiwalled carbon nanotubes (NTs), dispersed in
the cholesteric liquid crystal (cholesteryl oleyl carbonate, COC), nematic 5CB
and their mixtures, were studied in the temperature range between 255 K and 363
K. The relative concentration X=COC/(COC+5CB)was varied within 0.0-1.0. The
concentration of NTs was varied within 0.01-5% wt. The value of X
affected agglomeration and stability of NTs inside COC+5CB. High-quality
dispersion, exfoliation, and stabilization of the NTs were observed in COC
solvent ("good" solvent). From the other side, the aggregation of NTs was very
pronounced in nematic 5CB solvent ("bad" solvent). The dispersing quality of
solvent influenced the percolation concentration , corresponding to
transition between the low conductive and high conductive states: e.g.,
percolation was observed at and for pure COC and 5CB,
respectively. The effects of thermal pre-history on the heating-cooling
hysteretic behavior of electrical conductivity were studied. The mechanism of
dispersion of NTs in COC+5CB mixtures is discussed. Utilization of the mixtures
of "good" and "bad" solvents allowed fine regulation of the dispersion,
stability and electrical conductivity of LC+NTs composites. The mixtures of COC
and 5CB were found to be promising for application as functional media with
controllable useful chiral and electrophysical properties.Comment: 10 pages, 9 figure
Academic physical education system: questionnaire survey to rate student satisfaction
Objective of the study was to analyze the student satisfaction with the academic physical education servic
Research of the movement of agricultural aggregates using the methods of the movement stability theory
ArticleThe theory of the movement stability is of crucial practical importance for mobile
agricultural machines and machine aggregates, since it determines how qualitative and stable
their performance is in a particular technological process. It is especially urgent To ensure stable
movement for operation at high speeds of contemporary agricultural aggregates. The aim of this
investigation is detailed examination of criteria for the stability assessment of a mechanical
system used in agriculture, enabling their wide application in order to study the performance of
the system in the case when it is affected by random forces that were not taken into account in
the original model. The considered calculation methods and examples of their application make
it possible to evaluate the performance of complex dynamic systems without numerical solution
of complicated differential equations of the movement in the presence of external disturbances.
The considered example of the stability determination of the movement of a trailed cultivator
showed that this research method can be successfully used for practical purposes. Besides, a
differential equation of disturbed movement has been composed for an actually symmetrical
trailed agricultural machine with a particular mass, which moves at a constant forward speed
under the impact of summary resistance force running along the symmetry axis of the cultivator
and is applied at its centre of gravity. Reduced to normal Cauchy form, this equation was solved
on the PC, which made it possible to determine immediately the conditions for stable movement
of the trailed cultivator
GTO complex implementation technology for educational system
The study analyzes practical experience of the GTO Complex implementation project at Belgorod State National Research University with a special emphasis on the GTO Complex implementation process control mechanism including the following modules: progress test, regulatory, design and corporate management module
Research of the movement of agricultural aggregates using the methods of the movement stability theory
The theory of the movement stability is of crucial practical importance for mobile agricultural machines and machine aggregates, since it determines how qualitative and stable their performance is in a particular technological process. It is especially urgent To ensure stable movement for operation at high speeds of contemporary agricultural aggregates. The aim of this investigation is detailed examination of criteria for the stability assessment of a mechanical system used in agriculture, enabling their wide application in order to study the performance of the system in the case when it is affected by random forces that were not taken into account in the original model. The considered calculation methods and examples of their application make it possible to evaluate the performance of complex dynamic systems without numerical solution of complicated differential equations of the movement in the presence of external disturbances. The considered example of the stability determination of the movement of a trailed cultivator showed that this research method can be successfully used for practical purposes. Besides, a differential equation of disturbed movement has been composed for an actually symmetrical trailed agricultural machine with a particular mass, which moves at a constant forward speed under the impact of summary resistance force running along the symmetry axis of the cultivator and is applied at its centre of gravity. Reduced to normal Cauchy form, this equation was solved on the PC, which made it possible to determine immediately the conditions for stable movement of the trailed cultivator
Physical properties of thermoelectric zinc antimonide using first-principles calculations
We report first principles calculations of the structural, electronic,
elastic and vibrational properties of the semiconducting orthorhombic ZnSb
compound. We study also the intrinsic point defects in order to eventually
improve the thermoelectric properties of this already very promising
thermoelectric material. Concerning the electronic properties, in addition to
the band structure, we show that the Zn (Sb) crystallographically equivalent
atoms are not exactly equivalent from the electronic point of view. Lattice
dynamics, elastic and thermodynamic properties are found to be in good
agreement with experiments and they confirm the non equivalency of the zinc and
antimony atoms from the vibrational point of view. The calculated elastic
properties show a relatively weak anisotropy and the hardest direction is the y
direction. We observe the presence of low energy modes involving both Zn and Sb
atoms at about 5-6 meV, similarly to what has been found in Zn4Sb3 and we
suggest that the interactions of these modes with acoustic phonons could
explain the relatively low thermal conductivity of ZnSb. Zinc vacancies are the
most stable defects and this explains the intrinsic p-type conductivity of
ZnSb.Comment: 33 pages, 8 figure
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