5,514 research outputs found
Broken space-time symmetries and mechanisms of rectification of ac fields by nonlinear (non)adiabatic response
We consider low-dimensional dynamical systems exposed to a heat bath and to
additional ac fields. The presence of these ac fields may lead to a breaking of
certain spatial or temporal symmetries which in turn cause nonzero averages of
relevant observables. Nonlinear (non)adiabatic response is employed to explain
the effect. We consider a case of a particle in a periodic potential as an
example and discuss the relevant symmetry breakings and the mechanisms of
rectification of the current in such a system.Comment: 11 pages, 10 figure
Синтез цифрового регулятора головного контуру триконтурної системи лінійного електроприводу робочого органу механізму бортової авіаційної техніки
Goal The purpose of the article is to further develop analytical methods for calculating and synthesizing power electronics systems with deep pulse width modulation (PWM). A three-circuit linear electric drive system for positioning the working body of the mechanism of onboard aircraft equipment, in which the linear electric motor is controlled from a pulse width converter (PWC), is considered. The power converter is included in the current loop. It has a noticeable effect on the level of current ripple, travel speed and positioning accuracy of the operating mechanism of a linear electric drive. Methodology. To analyze the processes in the current loop, a discrete transfer function of a pulse-width converter for PWM in the final zone and «in the large» is obtained on the basis of the statistical linearization of the modulation characteristics of the multi-loop PWM model. The modulation characteristic of each circuit of the model is obtained as a result of the Fourier series expansion in Walsh functions of the output voltage of the PWM during the PWM process. Statistical linearization of modulation characteristics is performed based on Hermite polynomials. Results. During the analysis, discrete transfer functions of closed current loops, velocity and open loop position were obtained, for which a digital controller was synthesized in the form of a recursive filter. Originality. The parameters of the regulator links are found, which make it possible to complete the transient process in four PWC switching periods with an overshoot of no more than 6 %. The analysis of the speed-optimized positioning process of a linear electric drive based on the LED AT 605TU motor is carried out. Practical significance. The purpose of the analysis was to establish the relationship between the switching period of the PWM and the value of the uncompensated constant, at which the pulsations of the positioning process are minimal while ensuring the minimum overshoot and maximum speed. It was found that the specified requirements are satisfied by the ratio between the switching period, PWC and uncompensated constant in the range of one or two.В триконтурній системі лінійного електроприводу, робочий орган якого реалізує поступальне переміщення при виконанні команди бортового комп’ютера літального апарату, врахований вплив пульсацій широтно-імпульсного перетворювача постійної напруги на процес позиціонування. З умови кінцевої тривалості процесу позиціонування синтезовано цифровий регулятор головного контуру системи і запропонована його реалізація у вигляді рекурсивного цифрового фільтру
Vortex and translational currents due to broken time-space symmetries
We consider the classical dynamics of a particle in a -dimensional
space-periodic potential under the influence of time-periodic external fields
with zero mean. We perform a general time-space symmetry analysis and identify
conditions, when the particle will generate a nonzero averaged translational
and vortex currents. We perform computational studies of the equations of
motion and of corresponding Fokker-Planck equations, which confirm the symmetry
predictions. We address the experimentally important issue of current control.
Cold atoms in optical potentials and magnetic traps are among possible
candidates to observe these findings experimentally.Comment: 4 pages, 2 figure
ОЦЕНКА ЭНЕРГЕТИЧЕСКОЙ ЕФФЕКТИВНОСТИ ПАРАЛЛЕЛЬНОГО КВАЗИРЕЗОНАНСНОГО ПРЕОБРАЗОВАТЕЛЯ
The processing in experimental specimen of parallel quasi-resonant zero current switch converter (QR-ZCS) is considered. The advantages of QR-ZCS’ structural design are shown. The results of experimental researches of energy efficiency of parallel QR-ZCS converter are published. References 3, tables 1, figures 2.Исследована работа экспериментального макета параллельного квазирезонансного импульсного преобразователя, переключаемого при нулевом токе(КРИП-ПНТ). Показаны достоинства его структурного построения. Приведены результаты экспериментальных исследований энергетической эффективности параллельного КРИП- ПНТ. Библ. 3, табл. 1, рис. 2
Electrochemical Sensors for Vanadium Determination
© Published under licence by IOP Publishing Ltd. This paper is dedicated to the problem of vanadium (V) determination by the means of voltammetry. The comparison of results obtained for two types of sensor: volume glassy-carbon electrode and screen printed carbon electrode are presented. The experimental data is recorded using the hardware and software of Novocontrol (Germany): electrochemical interface POT/GAL 15V 10A, frequency response analyzer Alpha-A, and software for data collection and data processing WinDETA. Two three-electrode cells has been studied: for the first one the bulk glassy carbon electrode, and for the second one the screen printed electrodes has been used as the working electrode. In the first case the reference electrode has been made from silver chloride and the counter electrode from steel wire. In case of the screen printed electrodes, the electrodes were placed on the same plate. The peak of vanadium (V) was obtained under the potential of 1.3 V. It was found that the growth of the vanadium concentration increases magnitude of the cathode current measured then the mentioned potential is applied. The screen printed carbon electrodes provides better sensitivity in comparison with the volume glassy-carbon electrodes due to the more explicit vanadium potential peak
Magnetic Properties of 2-Dimensional Dipolar Squares: Boundary Geometry Dependence
By means of the molecular dynamics simulation on gradual cooling processes,
we investigate magnetic properties of classical spin systems only with the
magnetic dipole-dipole interaction, which we call dipolar systems. Focusing on
their finite-size effect, particularly their boundary geometry dependence, we
study two finite dipolar squares cut out from a square lattice with
and , where is an angle between the direction of the lattice axis
and that of the square boundary. Distinctly different results are obtained in
the two dipolar squares. In the square, the ``from-edge-to-interior
freezing'' of spins is observed. Its ground state has a multi-domain structure
whose domains consist of the two among infinitely (continuously) degenerated
Luttinger-Tisza (LT) ground-state orders on a bulk square lattice, i.e., the
two antiferromagnetically aligned ferromagnetic chains (af-FMC) orders directed
in parallel to the two lattice axes. In the square, on the other
hand, the freezing starts from the interior of the square, and its ground state
is nearly in a single domain with one of the two af-FMC orders. These geometry
effects are argued to originate from the anisotropic nature of the
dipole-dipole interaction which depends on the relative direction of sites in a
real space of the interacting spins.Comment: 21 pages, 13 figures, submitted to Journal of Physical Society Japa
Multipoint Schur algorithm and orthogonal rational functions: convergence properties, I
Classical Schur analysis is intimately connected to the theory of orthogonal
polynomials on the circle [Simon, 2005]. We investigate here the connection
between multipoint Schur analysis and orthogonal rational functions.
Specifically, we study the convergence of the Wall rational functions via the
development of a rational analogue to the Szeg\H o theory, in the case where
the interpolation points may accumulate on the unit circle. This leads us to
generalize results from [Khrushchev,2001], [Bultheel et al., 1999], and yields
asymptotics of a novel type.Comment: a preliminary version, 39 pages; some changes in the Introduction,
Section 5 (Szeg\H o type asymptotics) is extende
- …