Local temperature perturbations in the boundary layer in regime of free viscous-inviscid interaction

We analyze the disturbed flow in the supersonic laminar boundary layer when local heated elements are placed on the surface. It is exhibited that these flows are described in terms of free interaction theory for specific sizes of thermal sources. We construct the numerical solution for flat supersonic problem in the viscous asymptotic layer in which the flow is described by nonlinear equations for vorticity, temperature with the interaction condition which provides influence of perturbations to the pressure in the main order.Comment: 9 pages, 5 figure

A novel free-electron laser single-pulse Wollaston polarimeter for magneto-dynamical studies

Here, we report on the conceptual design, the hardware realization, and the first experimental results of a novel and compact x-ray polarimeter capable of a single-pulse linear polarization angle detection in the extreme ultraviolet photon energy range. The polarimeter is tested by performing time resolved pump-probe experiments on a Ni80Fe20 Permalloy film at the M-2,M-3 Ni edge at an externally seeded free-electron laser source. Comparison with similar experiments reported in the literature shows the advantages of our approach also in view of future experiments

All-optical spin injection in silicon investigated by element-specific time-resolved Kerr effect

Understanding howa spin current flows across metal-semiconductor interfaces at pico- and femtosecond time scales is of paramount importance for ultrafast spintronics, data processing, and storage applications. However, the possibility to directly access the propagation of spin currents, within such time scales, has been hampered by the simultaneous lack of both ultrafast element-specific magnetic sensitive probes and tailoredwell-built and characterized metal-semiconductor interfaces. Here, by means of a novel free-electron laser-based element-sensitive ultrafast time-resolved Kerr spectroscopy, we reveal different magnetodynamics for the Ni M-2;3 and Si L-2;3 absorption edges. These results are assumed to be the experimental evidence of photoinduced spin currents propagating at a speed of similar to 0.2 nm/fs across the Ni/Si interface

Diffraction imaging of light induced dynamics in xenon-doped helium nanodroplets

We explore the light induced dynamics in superfluid helium nanodroplets with wide-angle scattering in a pump–probe measurement scheme. The droplets are doped with xenon atoms to facilitate the ignition of a nanoplasma through irradiation with near-infrared laser pulses. After a variable time delay of up to 800 ps, we image the subsequent dynamics using intense extreme ultraviolet pulses from the FERMI free-electron laser. The recorded scattering images exhibit complex intensity fluctuations that are categorized based on their characteristic features. Systematic simulations of wide-angle diffraction patterns are performed, which can qualitatively explain the observed features by employing model shapes with both randomly distributed as well as structured, symmetric distortions. This points to a connection between the dynamics and the positions of the dopants in the droplets. In particular, the structured fluctuations might be governed by an underlying array of quantized vortices in the superfluid droplet as has been observed in previous small-angle diffraction experiments. Our results provide a basis for further investigations of dopant–droplet interactions and associated heating mechanisms

On iterating concentration and periodic regimes at the anomalous diffusion in polymers

Diffusion of a penetrating liquid in a polymeric material does not often satisfy the classical diffusion equations and requires taking relaxational (viscoelastic) properties of the polymer into account. We investigate a boundary value problem on a bounded domain in space for the set of equations modelling this abnormal diffusion. It is proved that, for any sufficiently short time segment and any stress prescribed at the beginning of this segment, there exists a global in time weak solution of the boundary value problem (a pair: concentration - stress) such that the concentrations at the beginning and at the end of the segment are the same. Under an additional assumption on coefficients, existence of time-periodic weak solutions (without any restrictions of the period length) is shown.Comment: 26 pages, in Russia

МЕТОДИКА ПРОВЕРКИ В НАЗЕМНЫХ УСЛОВИЯХ ЛИНЕЙНОГО РАЗРЕШЕНИЯ ПО АЗИМУТУ В РАДИОЛОКАТОРЕ С СИНТЕЗОМ АПЕРТУРЫ КОСМИЧЕСКОГО БАЗИРОВАНИЯ

By working out of a radar with the aperture synthesis of the aerial (RAS) of space basing there is a necessity of its debugging and verification at the land conditions. The most difficult verification task is requirement performance on resolution maintenance of RAS on an azimuth. It is caused by the given resolution provided in RAS at an orbit during stable moving in space with a speed about 7,6 km/s. The verification method of maintenance of the demanded linear resolution of RAS on an azimuth in land conditions with turned synthesis of aerial aperture is offered. It operates when RAS is unmoved and objects of resolution are placed at a moving ship.При разработке радиолокатора с синтезом апертуры антенны (РСА) космического базирования возникает необходимость его отладки и проверки в наземных условиях. Наиболее сложно проверить выполнение требования по обеспечению разрешающей способности РСА по азимуту. Это обусловлено тем, что разрешающая способность по азимуту обеспечивается в РСА при его стабильном перемещении на орбите в космосе со скоростью около 7,6 км/с. Предложена методика проверки обеспечения требуемого линейного разрешения РСА по азимуту в наземных условиях с использованием обращенного синтеза апертуры, когда РСА неподвижен, а объекты разрешения размещены на движущемся носителе, в частности, на плавсредстве

Algunos indicadores del desarrollo del esquema de derivada de una función

El objetivo de esta investigación es caracterizar algunos indicadores del desarrollo del esquema de derivada en estudiantes de pos-secundaria. Usamos los niveles intra, inter y trans del desarrollo de un esquema propuestos por Piaget y García para caracterizar el uso flexible que los estudiantes hacen de la equivalencia lógica entre diferentes elementos matemáticos cuando resuelven un problema, como un indicador del desarrollo del esquema de derivada. Este indicador ayuda a explicar la transición entre los niveles inter y trans de desarrollo del esquema derivada