The SCR flare of 16 February 1984 as recorded by the Sayan spectrograph

The Sayan cosmic ray (CR) spectrograph recorded an SCR flare that occurred on 16 February 1984. Data from both 1-hour and 110-minute duration measurements in 10 channels with different energy sensitivity (of neutron monitors HM-64 located at different depths in the atmosphere, and of a neutron, multiple neutron and rigid mumeson component lead-less detector) is presented. The parameters of the SCR variation spectrum are evaluated and it is shown that the recording of multiple neutrons at the same geographic point and at the same level in the atmosphere provides information similar to that from a spectrographic complex of instruments

Simulation of the turbulent structure of a flow and heat transfer in an ascending polydisperse bubble flow

We report on the results of numerical simulation of the turbulent structure of a flow in a vertical polydisperse gas—liquid stream in a tube. The mathematical model is based on the application of the Euler description taking into account the inverse effect of bubbles on the averaged characteristics and turbulence of the carrying phase. Turbulent characteristics of the liquid are calculated using the model of transfer of Reynolds stress tensor components. The variation of the number of bubbles is described using the model of average volume of a bubble taking into account their splitting, coalescence, and expansion upon a change in the gas temperature. The effect of the change in the volumetric consumption gas content, the initial temperature of the liquid, and its velocity on the structure of the flow and on the heat transfer in the two-phase flow is analyzed. The addition of the gas phase to the turbulent liquid causes an increase in the heat transfer by more than 2.5 times. Comparison of the results of simulation with experimental data shows that the approached developed here makes it possible to simulate bubble turbulent flows with heat exchange with the tube wall in a wide range of gas contents

Film cooling effectiveness with injection through circular holes embedded in a transverse trench

Results of a numerical study of the thermal effectiveness of a gas wall screen implemented via gas blowing through cylindrical inclined holes embedded in a transverse trench are reported. The calculations were performed using 3D Reynolds-averaged Navier–Stokes equations, with the flow turbulence being modeled by means of the Reynolds-stress model. Blowing into the trench was compared to the conventional cooling technique using gas blowing without a trench. The film cooling effectiveness with gas injection through circular holes embedded in trench exceeds significantly the effectiveness of blowing without a trench. Such a method of coolant supply into the flow proved to be especially advantageous at high blowing ratios. Due to the formation of vortical structures inside the trench, a more uniform cooling flow in the spanwise direction can be achieved. A comparative analysis is indicative of acceptable qualitative agreement of the experimental and predicted data

Negative Magnetoresistance in the Nearest-neighbor Hopping Conduction

We propose a size effect which leads to the negative magnetoresistance in granular metal-insulator materials in which the hopping between two nearest neighbor clusters is the main transport mechanism. We show that the hopping probability increases with magnetic field. This is originated from the level crossing in a few-electron cluster. Thus, the overlap of electronic states of two neighboring clusters increases, and the negative magnetoresistance is resulted.Comment: Latex file, no figur

Generation of unipolar half-cycle pulse via unusual reflection of a single-cycle pulse from an optically thin metallic or dielectric layer

We present a significantly different reflection process from an optically thin flat metallic or dielectric layer and propose a strikingly simple method to form approximately unipolar half-cycle optical pulses via reflection of a single-cycle optical pulse. Unipolar pulses in reflection arise due to specifics of effectively one-dimensional pulse propagation. Namely, we show that in considered system the field emitted by a flat medium layer is proportional to the velocity of oscillating medium charges instead of their acceleration as it is usually the case. When the single-cycle pulse interacts with linear optical medium, the oscillation velocity of medium charges can be then forced to keep constant sign throughout the pulse duration. Our results essentially differ from the direct mirror reflection and suggest a possibility of unusual transformations of the few-cycle light pulses in linear optical systems