Expanded graphite as a support for Ni/carbon composites

Expanded graphite decorated with nickel oxide particles (EG_NiO) has been synthesized through electrochemical oxidation of natural graphite in an aqueous nickel nitrate solution followed by a heat treatment. EG_NiO was used to prepare nickel/carbon composites using two techniques: (a) hydrogen reduction of nickel oxide particles loaded on the expanded graphite surface and (b) pyrolysis of coal tar pitch-impregnated EG_NiO blocks. The EG_NiO as well as the nickel/carbon composites have been characterized by X-ray diffraction, scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy and selected area electron diffraction.     

Interaction of an ultrashort electromagnetic pulse with a molecular hydrogen ion

Analytical expressions that describe the spectrum of reemission during the interaction of an ultrashort electromagnetic pulse with a molecular hydrogen ion are obtained. The role of the orientation of the axis of the molecular ion during this interaction is studied. It is shown that the spectra of reemitted photons strongly depend on the orientation of molecular targets.     

On the ultimate sensitivity of nonlinear-modulation method of crack detection

Despite the increasing number of impressive demonstrations of the high sensitivity of nonlinear-acoustic methods of damage detection, the physical factors which limit the ultimate sensitivity of this approach are not yet clearly understood. In this paper we perform the corresponding analysis and formulate criteria determining the minimal size of detectable cracks. The relation of the nonlinear-modulation technique to the linear frequency-shift technique is discussed. The analysis is particularly focused on the nonlinear-modulation resonance technique. It is based on rather general properties of the defects consistently predicted by various rigorous cracks models. The obtained conclusions are compared with experimental data obtained in nonlinear-modulation experiments on the detection of cracks in railway axles and wheels.     

Nonlinear control for reactive navigation of a nonholonomic robot for environmental nongradient‐based extremum seeking in maze‐like scenes

A single Dubins car‐like mobile robot travels with a constant speed in a planar workspace cluttered with arbitrarily complex obstacles, possibly maze‐like ones. An unknown scalar field is defined on the plane. The sensors supply the robot with the field value at its current location and its distance to the nearest obstacle. We present a new control law that drives the robot to the location where the field attains its maximum, while avoiding collisions with the obstacles. This is justified by a mathematically rigorous global convergence result and is confirmed via computer simulations. The proposed algorithm does not use gradient estimation and is nondemanding with respect to computation and motion. Copyright © 2017 John Wiley & Sons, Ltd.     

Increasing the stability of pump operation in metering solutions of polyoxadiazole in sulfuric acid

Conclusions The basic reasons for failure in the operation of spinning gear pumps in metering solutions of polyoxadiazole in concentrated sulfuric acid have been studied.The possibility of eliminating blockage of gear pumps, reducing nonuniformity in delivery of spinning solution, and considerably increasing the stability of spinning Oksalon fibre has been demonstrated.Translated from Khimicheskie Volokna, No. 2, pp. 54–55, March–April, 1986.     

Uranium behavior in the process of ashing the wood base of spent chemical absorbers

The results of investigating the wood base ashing of spent chemical absorbers of MW and MMW types containing uranium have been given. The acceptable ashing temperature has been shown to be equal to 600–700°C, with a process duration of no less than an hour. To decrease the volume of the ash residues, a crushing stage is required. The volume of the ash residues comprises 6–10% of the volume of source absorbers; furthermore, their mass decreases threefold depending on the uranium content in the source material. Ways to decrease the temperature of the wood base ashing, including those that use burning promoters, have been contemplated.