Some Properties of Smooth Convex Functions and Newton’s Method

Doklady Mathematics - New properties of convex infinitely differentiable functions related to extremal problems are established. It is shown that, in a neighborhood of the solution, even if the...     

Influence of Porosity on Fracture Toughness of Hydroxyapatite/Multi-Walled Carbon Nanotubes Biocomposite Materials

Russian Physics Journal - The paper analyzes the influence of porosity of hydroxyapatite (HA)/multi-wall carbon nanotubes (MWCNTs) composites on their fracture toughness. It is found that two...     

CuBr-Ne-HBr laser with a high repetition frequency of the lasing pulses at a reduced energy deposition in the discharge

Experimental and computer studies of the CuBr laser with periodic-pulse pumping are performed with and without addition of HBr. The analysis based on the numerical simulation reveals how additions improve the lasing characteristics of this laser at both typical (10 to 20 kHz) and higher (up to 100 kHz) excitation pulse repetition frequencies during the operation with a low energy deposition in the discharge. This allows the lasing pulse repetition frequency to be increased in the experiment to 750 kHz, which does not seem to be a limit as yet.     

Study of a Pulsed Air Flow in a Large Vacuum Chamber by Means of a Commercial Ionization Gauge

Technical Physics - A method for creating a pressure gradient by pulsed injection of air into a large vacuum chamber for laboratory simulation of plasma phenomena in a vertically nonuniform...     

Generalized fast automatic differentiation technique

A new efficient technique intended for the numerical solution of a broad class of optimal control problems for complicated dynamical systems described by ordinary and/or partial differential equations is investigated. In this approach, canonical formulas are derived to precisely calculate the objective function gradient for a chosen finite-dimensional approximation of the objective functional.     

Simulation of mesospheric-composition disturbances under the action of high-altitude discharges (sprites)

Recent measurements show that a mesospheric electric discharge (sprite) can provoke disturbances in the chemical composition of the mesosphere. In this paper, we propose a plasmachemical system of equations which allows one to describe the complex relationship among chemical components during the discharge. Disturbances of the mesospheric ion composition are analyzed under the night-time and daytime conditions at an altitude of 75 km, which is typical of the sprite initiation and at an altitude of 85 km where the diffuse region of discharge is usually observed. The most probable scenarios of development of the electric-field and electron-temperature disturbances, which are characteristic of the diffusive and streamer regions of the sprite, are simulated. The value and characteristic time of disturbances of the main ion components (O₂ ⁺, NO⁺, H₃O⁺, H₅O₂ ⁺, and N₂ ⁺) are evaluated. The obtained values of the electron-density disturbances are in agreement with experimental and theoretical data. It was established that the sprite series, which are recorded over the vast stratified regions of mesoscale convection systems, can lead to generation of comparatively long-lived disturbances in the ion composition of mesospheric plasma.     

Metal-vapor lasers for problems of atmospheric optics

The paper formulates the requirements for metal-vapor lasers as sources of coherent radiation for atmospheric optics and identifies ways to realize the desired laser performance. Institute of Atmospheric Optics of the Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 88–95, August, 1999.