A multichannel spectrometer for detecting γ rays in a wide range of time intervals during pulse neutron irradiation

A versatile spectrometer has been developed for measuring the nuclear radiation spectrum in discrete time intervals. The design and operating principle of the spectrometer are described. Since the main logical part is based on a field programmable gate array, time intervals may be tuned in a wide range without changing the spectrometer hardware. The test experiments have demonstrated the spectrometer applicability for measuring the amplitude and timing parameters of the γ response when an analyzed sample is irradiated with a pulsed neutron flux. This device can be used to solve many problems of nondestructive testing, e.g., spectrometric neutron logging, detection of explosives, identification and characterization of fissile materials.     

The effect of side chain length on hydrodynamic and conformational characteristics of polyimide-graft-polymethylmethacrylate copolymers in thermodynamically good solutions

Samples of graft-copolymers with polyimide backbones and poly(methyl methacrylate) side chains synthesized by ATRP of methylmethacrylate on polyimide macroinitiator are investigated by ¹H NMR, GPC, static and dynamic light scattering, sedimentation, and viscosimetry in chloroform and ethyl acetate solutions. Hydrodynamic and conformational behavior of graft-copolymers is well-described by the wormlike spherocylinder and Porod wormlike chain models. Samples of graft-copolymers have high equilibrium rigidity, the Kuhn segment length grows from 20 to 95 nm with the lengthening of side chains. The equilibrium rigidity and hydrodynamic diameter of the investigated graft-copolymers depend on the molar mass M of side chains as M ^0.7.     

Influence of Macromolecular Brushes with Polyimide Backbones and Poly(methyl methacrylate) Side Chains on Structure,Physical, and Transport Properties of Polyphthalamide

Composite films based on polyamide (poly(m-phenylene-iso-phthalamide)) (PA) and a brush-like polymer with polyimide (PI) backbone and side poly(methyl methacrylate) chains (PI-PMMA) were prepared by mixing individual solutions of PA and PI-PMMA and subsequent film casting. Macromolecular brushes with the same backbone length and density of side chains but with various lengths of side PMMA chains were synthesized via activator generated by electron transfer atom transfer radical polymerization. Interactions between PA and PI-PMMA, as well as distribution of PI-PMMA filler inside the PA matrix, were studied by viscometry, dynamic light scattering, differential scanning calorimetry, scanning electron microscopy, and IR spectroscopy. The mechanical properties of polymer samples were also investigated. Microphase separation was revealed in PA/PI-PMMA films. The length of side chains influences interactions between PA and PI-PMMA. At the same time, the degree of reduction in the rigidity parameters and in the elasticity parameter depends on the side chain length. Diffusion membranes were prepared on the basis of compositions with the best mechanical properties; these membranes proved to be highly efficient in pervaporation of methanol–hexane mixture. It was established that the fluxes and separation factors of the studied membranes are several times higher as compared to the corresponding characteristics of known commercial membranes. POLYM. ENG. SCI., 60:481–490, 2020. © 2019 Society of Plastics Engineers     

Active resistance of the inductor under induction heating of inner cylindrical surfaces

Practical diagrams are presented for evaluating the active ac resistance of the inductor with and without a magnetic circuit in the inner cavity of the heated article.     

A new possibility of building up thin diamond films in precipitation of carbon from the gaseous phase

A new method for building up thin diamond films is suggested based on the difference in the rates of sublimation of graphite and diamond. It is recommended that this method be used for producing diamond films at temperatures above ∼1000°C without application of a chemical etching agent. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 454–457, March–April, 2000.