2,058 research outputs found
Hydrodynamic model for electron-hole plasma in graphene
We propose a hydrodynamic model describing steady-state and dynamic electron
and hole transport properties of graphene structures which accounts for the
features of the electron and hole spectra. It is intended for electron-hole
plasma in graphene characterized by high rate of intercarrier scattering
compared to external scattering (on phonons and impurities), i.e., for
intrinsic or optically pumped (bipolar plasma), and gated graphene (virtually
monopolar plasma). We demonstrate that the effect of strong interaction of
electrons and holes on their transport can be treated as a viscous friction
between the electron and hole components. We apply the developed model for the
calculations of the graphene dc conductivity, in particular, the effect of
mutual drag of electrons and holes is described. The spectra and damping of
collective excitations in graphene in the bipolar and monopolar limits are
found. It is shown that at high gate voltages and, hence, at high electron and
low hole densities (or vice-versa), the excitations are associated with the
self-consistent electric field and the hydrodynamic pressure (plasma waves). In
intrinsic and optically pumped graphene, the waves constitute quasineutral
perturbations of the electron and hole densities (electron-hole sound waves)
with the velocity being dependent only on the fundamental graphene constants.Comment: 11 pages, 6 figure
Improving the accuracy of a time lens
Cataloged from PDF version of article.A method for improving the accuracy of temporal imaging with an imperfect time lens is proposed. Signal distortion arising from complicated dispersion of the delay lines can be reduced considerably by appropriate choice of the phase-modulation function including the second harmonic of the basic modulation frequency and a specific phase shift of the modulation with respect to the main signal. The method is of particular interest for picosecond and femtosecond optical pulse generation. © 1997 Optical Society of Americ
СИСТЕМАТИЗАЦІЯ НАУКОВИХ ДОСЛІДЖЕНЬ З ПРОБЛЕМ ВИТРАТ НА ВИРОБНИЦТВО ПРОДУКЦІЇ
An important condition for the production of industrial enterprises is the effective use and restoration of productive resources, which are based on competent management process of reducing production costs. The article by bibliometric and bibliographic research, critical analysis and systematization of scientific papers published in scientific bulletin and proceedings problems in the areas of accounting, development, evaluation, analysis and management of production costs, their grouping by year, within the meaning of articles in the section authors and countries.Важным условием развития производственной деятельности промышленных предприятий является эффективное использование и воспроизводство производственных ресурсов, в основе которых лежит грамотное управление процессом снижения производственных затрат. В статье осуществлено библиометрическое и библиографическое исследование, критический анализ и систематизацию научных работ, напечатанных в научных вестниках и сборниках научных трудов по направлениям проблем учета, формирования, оценки, анализа и управления затратами на производство, их группировки по годам, по содержанию статей, в разрезе авторов и стран.Важливою умовою розвитку виробничої діяльності промислових підприємств є ефективне використання та відтворення виробничих ресурсів, в основі яких лежить грамотне управління процесом зниження виробничих витрат. В статті здійснено бібліометричне та бібліографічне дослідження, критичний аналіз та систематизацію наукових робіт, надрукованих в наукових вісниках та збірниках наукових праць за напрямами проблем обліку, формування, оцінки, аналізу та управління витратами на виробництво, їх групування за роками, за змістом статей, в розрізі авторів та країн
Radiative cooling of H3O+ and its deuterated isotopologues
In conjunction with ab initio potential energy and dipole moment surfaces for
the electronic ground state, we have made a theoretical study of the radiative
lifetimes for the hydronium ion HO and its deuterated isotopologues.
We compute the ro-vibrational energy levels and their associated wavefunctions
together with Einstein coefficients for the electric dipole transitions. A
detailed analysis of the stability of the ro-vibrational states have been
carried out and the longest-living states of the hydronium ions have been
identified. We report estimated radiative lifetimes and cooling functions for
temperatures 200 K. A number of long-living meta-stable states are
identified, capable of population trapping.Comment: Phys. Chem. Chem. Phys., 201
The Capacitive Magnetic Field Sensor
The results of a study of sensitive element magnetic field sensor are represented in this paper. The sensor is based on the change of the capacitance with an active dielectric (ferrofluid) due to the magnitude of magnetic field. To prepare the ferrofluid magnetic particles are used, which have a followingdispersion equal to 50 < [the empty set] <= 56, 45 < [the empty set] <= 50, 40 < [the empty set] <=45 and [the empty set] <= 40 micron of nanocrystalline alloy of brand 5BDSR. The dependence of the sensitivity of the capacitive element from the ferrofluid with different dispersion of magnetic particles is considered. The threshold of sensitivity and sensitivity of a measuring cell with ferrofluid by a magnetic field was determined. The experimental graphs of capacitance change of the magnitude of magnetic field are presented
Duo: a general program for calculating spectra of diatomic molecules
Duo is a general, user-friendly program for computing rotational,
rovibrational and rovibronic spectra of diatomic molecules. Duo solves the
Schr\"{o}dinger equation for the motion of the nuclei not only for the simple
case of uncoupled, isolated electronic states (typical for the ground state of
closed-shell diatomics) but also for the general case of an arbitrary number
and type of couplings between electronic states (typical for open-shell
diatomics and excited states). Possible couplings include spin-orbit, angular
momenta, spin-rotational and spin-spin. Corrections due to non-adiabatic
effects can be accounted for by introducing the relevant couplings using
so-called Born-Oppenheimer breakdown curves.
Duo requires user-specified potential energy curves and, if relevant, dipole
moment, coupling and correction curves. From these it computes energy levels,
line positions and line intensities. Several analytic forms plus interpolation
and extrapolation options are available for representation of the curves. Duo
can refine potential energy and coupling curves to best reproduce reference
data such as experimental energy levels or line positions. Duo is provided as a
Fortran 2003 program and has been tested under a variety of operating systems
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