150 research outputs found
Відображення розвитку науки України та Євросоюзу в реферативній базі даних SCOPUS
Досліджено публікаційну активність України та Євросоюзу за галузями науки. Розглянуто динаміку кількості публікацій, що припадають на одного дослідника впродовж 1996-2010 рр. Виконано порівняння відображення кількості публікацій БД Scopus у ВВП та витратах на НДДКР країн в розрахунку на кожен 1 млн. дол. США.Исследована публикационная активность Украины и Евросоюза по отраслям науки. Рассмотрена динамика количества публикаций, которые приходятся на одного исследователя на протяжении 1996–2010 гг. Сделано сравнение отображения количества публикаций БД Scopus в ВВП и затратах на НДДКР стран в расчете на каждый 1 млн. дол. США.The publication activity by fields of science of Ukraine and the European Union was investigated. The dynamics of the number of publications per 1 researcher was considered during 1996–2010 years. Countries comparison by the number of publications reflecting in GDP and R&D expenditures per 1 million U.S. dollars measurements in the abstract database Scopus was done
Multiparticle Biased DLA with surface diffusion: a comprehensive model of electrodeposition
We present a complete study of the Multiparticle Biased Diffusion-Limited
Aggregation (MBDLA) model supplemented with surface difussion (SD), focusing on
the relevance and effects of the latter transport mechanism. By comparing
different algorithms, we show that MBDLA+SD is a very good qualitative model
for electrodeposition in practically all the range of current intensities {\em
provided} one introduces SD in the model in the proper fashion: We have found
that the correct procedure involves simultaneous bulk diffusion and SD,
introducing a time scale arising from the ratio of the rates of both processes.
We discuss in detail the different morphologies obtained and compare them to
the available experimental data with very satisfactory results. We also
characterize the aggregates thus obtained by means of the dynamic scaling
exponents of the interface height, allowing us to distinguish several regimes
in the mentioned interface growth. Our asymptotic scaling exponents are again
in good agreement with recent experiments. We conclude by discussing a global
picture of the influence and consequences of SD in electrodeposition.Comment: 15 pages, 20 figures, accepted for publication in Physical Review
Magnetic-field dependence of electron spin relaxation in n-type semiconductors
We present a theoretical investigation of the magnetic field dependence of
the longitudinal () and transverse () spin relaxation times of
conduction band electrons in n-type III-V semiconductors. In particular, we
find that the interplay between the Dyakonov-Perel process and an additional
spin relaxation channel, which originates from the electron wave vector
dependence of the electron -factor, yields a maximal at a finite
magnetic field. We compare our results with existing experimental data on
n-type GaAs and make specific additional predictions for the magnetic field
dependence of electron spin lifetimes.Comment: accepted for publication in PRB, minor changes to previous manuscrip
Weak localization in InSb thin films heavily doped with lead
The paper reports on the investigations of the weak localization (WL) effects
in 3D polycrystalline thin films of InSb. The films are closely compensated
showing the electron concentration n>10^{16} cm^{-3} at the total concentration
of the donor and acceptor type structural defects >10^{18} cm^{-3}. Unless
Pb-doped, the InSb films do not show any measurable or show very small WL
effect at 4.2 K. The Pb-doping to the concentration of the order of 10^{18}
cm^{-3} leads to pronounced WL effects below 7 K. In particular, a clearly
manifested SO scattering is observed. From the comparison of the experimental
data on temperature dependence of the magnetoresistivity and sample resistance
with the WL theory, the temperature dependence of the phase destroying time is
determined. The determination is performed by fitting theoretical terms
obtained from Kawabata's theory to experimental data on magnetoresistance. It
is concluded that the dephasing process is connected to three separate
interaction processes. The first is due to the SO scatterings and is
characterized by temperature-independent relaxation time. The second is
associated with the electron-phonon interaction. The third dephasing process is
characterized by independent on temperature relaxation time tau_c. This
relaxation time is tentatively ascribed to inelastic scattering at extended
structural defects, like grain boundaries. The resulting time dephasing time
shows saturation in its temperature dependence. The temperature dependence of
the resistance of the InSb films can be explained by the electron-electron
interaction for T2 K.Comment: 15 pages with 5 figure
Early stages of ramified growth in quasi-two-dimensional electrochemical deposition
I have measured the early stages of the growth of branched metal aggregates
formed by electrochemical deposition in very thin layers. The growth rate of
spatial Fourier modes is described qualitatively by the results of a linear
stability analysis [D.P. Barkey, R.H. Muller, and C.W. Tobias, J. Electrochem.
Soc. {\bf 136}, 2207 (1989)]. The maximum growth rate is proportional to
where is the current through the electrochemical cell,
the electrolyte concentration, and . Differences
between my results and the theoretical predictions suggest that
electroconvection in the electrolyte has a large influence on the instability
leading to ramified growth.Comment: REVTeX, four ps figure
Experimental investigation of the initial regime in fingering electrodeposition: dispersion relation and velocity measurements
Recently a fingering morphology, resembling the hydrodynamic Saffman-Taylor
instability, was identified in the quasi-two-dimensional electrodeposition of
copper. We present here measurements of the dispersion relation of the growing
front. The instability is accompanied by gravity-driven convection rolls at the
electrodes, which are examined using particle image velocimetry. While at the
anode the theory presented by Chazalviel et al. describes the convection roll,
the flow field at the cathode is more complicated because of the growing
deposit. In particular, the analysis of the orientation of the velocity vectors
reveals some lag of the development of the convection roll compared to the
finger envelope.Comment: 11 pages, 15 figures, REVTEX 4; reference adde
Does ohmic heating influence the flow field in thin-layer electrodeposition?
In thin-layer electrodeposition the dissipated electrical energy leads to a
substantial heating of the ion solution. We measured the resulting temperature
field by means of an infrared camera. The properties of the temperature field
correspond closely with the development of the concentration field. In
particular we find, that the thermal gradients at the electrodes act like a
weak additional driving force to the convection rolls driven by concentration
gradients.Comment: minor changes: correct estimation of concentration at the anode,
added Journal-re
Normal and lateral Casimir force: Advances and prospects
We discuss recent experimental and theoretical results on the Casimir force
between real material bodies made of different materials. Special attention is
paid to calculations of the normal Casimir force acting perpendicular to the
surface with the help of the Lifshitz theory taking into account the role of
free charge carriers. Theoretical results for the thermal Casimir force acting
between metallic, dielectric and semiconductor materials are presented and
compared with available experimental data. Main attention is concentrated on
the possibility to control the magnitude and sign of the Casimir force for
applications in nanotechnology. In this respect we consider experiments on the
optical modulation of the Casimir force between metal and semiconductor test
bodies with laser light. Another option is the use of ferromagnetic materials,
specifically, ferromagnetic dielectrics. Under some conditions this allows to
get Casimir repulsion. The lateral Casimir force acting between sinusoidally
corrugated surfaces can be considered as some kind of noncontact friction
caused by zero-point oscillations of the electromagnetic field. Recent
experiments and computations using the exact theory have demonstrated the role
of diffraction-type effects in this phenomenon and the possibility to get
asymmetric force profiles. Conclusion is made that the Casimir force may play
important role in the operation of different devices on the nanoscale.Comment: 27 pages, 13 figures; Invited keynote lecture at the 2nd
International Conference on Science of Friction, Ise-Shima, Mie, Japan,
September 13-18, 2010; to appear in J. Phys.: Conf. Se
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