Analysis of the Particles’ Movement Over the Flat and Profiled Rotating Discs surface in the Velocity Layer of the Viscous Gas

Experiments on the rotating in the air cones with vertex angle β = 120º and flat disc shown that on frequencies Ω ≥ 2.5 hertz exists a qualitative difference in movement for the particles with diameters d ≈ 1 mm and d ≈ 0.1 mm. The particles with d ≈ 0.1 mm move in the near-surface region, the particles with d ≈ 1 mm jump up to 3 cm. Comparison of the spherical and aspheric (ellipsoid with axles d, d and 4 /3 d) particles' kinematics moving shown the inevitability of the large particles jump occurrence. Large particles come to self-oscillation regime by reason of periodically appearance of the Magnus force. Small particles are localized in the velocity layer

Повышение мощности и улучшение направленности излучения широкоапертурных гетеролазеров при оптимизации размеров брэгговской решетки

We investigate the dynamics of heterolasers with finite-length planar Bragg structures. Based on the analysis of the dispersion equation describing the eigenwaves propagation in a Bragg structure, we present a physical interpretation of selection of modes with frequencies higher than the stopband. We demonstrate the improvement of stability by using the Bragg structures with transverse dimensions lower than the width of the active area of DFB heterolasers. As a result, the single-mode oscillation regime is sustained over a wider range of pump levels, and, correspondingly, of the output radiation power.

Квантовые осцилляции магнетосопротивления в гетероструктурах HgCdTe/HgTe/HgCdTe с инвертированным зонным спектром

The effects observed in the Shubnikov - de Haas oscillation regime in the HgCdTe/HgTe/HgCdTe heterostructure with a wide (20.3 nm) HgTe quantum well with an inverted band structure are discussed. In a topologically trivial 2D system, Pi(Greek letter) - shift of magnetooscillation phase is found. A thorough experimental study and theoretical analysis of the data is presented to understand the physical causes of this anomalous phase shift. The value of the effective electron mass m_c/m_0 = (0.022+-0.002), obtained from the region of doubly degenerate peaks of magnetoresistance, is approximately half the theoretical estimates. In the region of stronger magnetic fields for nondegenerate peaks of magnetoresistance, we have m_c/m_0 = (0.034+-0.003), which is in good agreement with both theoretical predictions and experimental results obtained from the analysis of activation conductivity in the quantum Hall effect regime. The reasons for this discrepancy are discussed.

Long-period variability of ocean circulation at different intensity of wind impact

Within the framework of a numerical model of a two-layer ocean with the depth of layers corresponding to average oceanic conditions, the evolution of large-scale circulation under the action of an external vorticity flow of different intensity with constant dissipation parameters is studied. The characteristic time scales of long-period oscillations of current energy at different values of wind impact, jet flow parameters, and the time-average level of total energy in the mode of long-period oscillations at different wind impact intensity are analyzed. The stability of the long-period oscillation regime under various initial conditions of the problem is discussed.

Исследование динамических пороговых характеристик VO-=SUB=-2-=/SUB=--переключателя в осцилляторном контуре

This paper investigates the dependence of the dynamic threshold characteristics of a VO2-switch on the oscillation frequency of a self-oscillating circuit. A transitional oscillation regime related to the self-heating of the substrate is discovered. Proposed analytical formulas allow consider these regularities and having practical significance in designing oscillator neural networks based on VO2-switches.