A method for measuring the eigenfrequency of the fiber coil of a Sagnac interferometer

A method for determining the eigenfrequencies of the fiber coils used in sensors based on a Sagnac interferometer is proposed. In this method, the fiber coil is used as the main part of an external resonator of a laser diode. The method is simple and reliable, and a high accuracy of measurements is ensured.     

Preparation of finely dispersed nanographite

We have developed a convenient single-step method for producing stable nanographite dispersions from natural graphite in various solvents using high-power sonication. Nanographite dispersions in water are shown to be stable for several weeks, and aqueous nanographite dispersions containing a surfactant are stable for several months. Nanographite samples prepared from aqueous nanographite dispersions have been characterized by various physicochemical techniques (including X-ray diffraction and Raman spectroscopy). Interference microscopy, transmission and scanning electron microscopy, and atomic force microscopy have been used to examine the morphology and determine the size of nanographite particles. The nanographite platelets are 300–500 nm in lateral size and 20–40 nm in thickness, which corresponds to 30–50 graphene layers.     

Dependences of the detonation velocity and propellant performance of metallized explosives on the charge density and additive content

The dependences of the detonation velocity and the propellant performance measured using the M-40 technique on the charge density for aluminized explosives with different mass fraction of Al were studied. The fractions of the energy of Al combustion utilized during the chemical reactions and during the acceleration of the flyer plate were estimated. Regression dependences of the detonation velocity and the propellant performance on the charge density were obtained. The effect of the addition of particulate Al, Ti, Zr, and W in an amount of 5–30% on the detonation velocity of high-density explosive charges based on plasticized RDX was investigated. It is found that the reduction in the detonation velocity with the addition of various metallic additives is determined by the longitudinal sound velocity of the additive, and not by its density. Simple formulas for calculating the detonation parameters of high-density metallized explosives were obtained.     

Synthesis of phase shifters based on a single stepped transmission line with a stub

A two-criteria problem of the synthesis of differential phase shifters designed on the basis of a new structure-a symmetric stepped transmission line with a stub connected in the middle of the structure—is solved. Optimum parameters of such phase shifters are calculated for phase shifts φ₀ = 11.25°−135° and bandwidths of 40% and 67%. It is found that the wave impedances of the steps monotonically decrease from feeding lines to the structure center and optimum wave impedances of the stub and sections decrease with increasing φ₀. It is shown that structures with different stubs are analytically equivalent. Parameter values of the phase shifter are improved as compared to the parameter values of a known design. A 90° microstrip phase shifter is experimentally studied in a frequency band of 2–4 GHz. It is found that the maximum discrepancy between the theoretical and experimental characteristics is 5° and the maximum value of the standing-wave ratio is 1.11     

Obtaining Silicon-Carbide-Based Ceramics from Ash and Slag Wastes

Technical Physics Letters - The possibility of obtaining solid silicon-carbide-based ceramics from ash and slag wastes (ASWs) is demonstrated. The technological process contains three stages: (i)...     

Preparation, Structure, and Properties of Magnetic Materials Based on Co-Containing Nanoparticles

The recent experimental data on the preparation and properties of materials containing Co-based magnetic nanoparticles are summarized. Particular attention is focused on the synthesis of cobalt nanoparticles in rigid matrices (polymers, metals, and solid surfaces) and their static magnetic properties, which are of great importance for practical applications. The conclusion is made that surface effects play an important role in determining the magnetic properties of nanoparticles.     

Heat of explosion of commercial and brisant high explosives

Methods for determining the heat of explosion of high explosives (HEs) with ideal and nonideal processes of explosive decomposition are considered. It is shown that the heat of explosion is of significance for estimating the efficiency of commercial HEs and is used in the energetic characterization of the working capacity. The heat of explosion of brisant HEs is only part of the blast heat of explosion and is the heat content of gaseous detonation products during their isentropic expansion from the initial state to a certain expansion ratio (determined by experimental conditions). The heat of explosion can be obtained by thermodynamic calculations based on physically justified equations of state for fluids (gaseous detonation products in the chemical-reaction zone of the detonation wave in the supercritical state) and condensed nanocarbon phases (nanographite, nanodiamond, and liquid carbon). Experimental and calculated values of the heat of explosion are given. The thermodynamic calculation is inapplicable to commercial HEs because of the nonideal nature of their detonation. The heat of explosion of commercial HEs can be calculated using the Hess law. The heat of explosion of brisant HEs is not a measure of power. The power of HEs is characterized by the propellant performance. It is shown that even detonation velocity cannot be a measure of the power of HEs. The power and detonation parameters of brisant HEs are determined by the energy release density in unit volume of the chemical-reaction zone of the detonation wave and by the rate of energy release from the shock front rather than by the heat of explosion, which cannot be considered a universal characteristic. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 100–107, March–April, 2007.