Comment on Y.-H. Hsu et al., "electrical and mechanical fully coupled theory and experimental verification of Rosen-type piezoelectric transformers" [see reference [1]]

This letter discusses the difference between piezoelectric constitutive relations for the case of one-dimensional stress and the case of one-dimensional strain, and its implications in the modeling of Rosen piezoelectric transformers.     

Comparative Assessment of the Effect of Chemical and Radiation Factors on Workers and the General Public Resulting from the Salvaging of Nuclear-Powered Submarines

The results of observations performed over many years are used to make an assessment of the degree to which the concentration of chemical and radioactive substances escaping into the environment during salvaging of nuclear-powered submarines exceeds the admissable norms for workers at the main ship-repair facilities in Russia and for the general public in the surrounding territories. It is shown that the chemical substances are a determining factor in environmental contamination. Their content in the atmosphere and sea water exceeds the admissable norms near sources, on the territory of the enterprises, and (for individual indicators) at populated points. Under these conditions, the concentration of technogenic radionuclides does not exceed the admissable norms and its damaging effect on man is hundreds and thousands of times less than that of chemicals.     

Special Features of Fracture of Steels from Partially-Alloyed Powders

Special features of fracture of structural steels 45N2D2M and 45N4D2M manufactured by pressing with subsequent sintering from partially alloyed iron powders are studied. Impact bending tests of specimens with different levels of retained porosity show two kinds of fracture, i.e., intraparticle cleavage and interparticle dimple fracture. In addition, the surfaces of the “initial” pores come out to the fracture surface. Other conditions being equal, growth in porosity decreases the proportion of the brittle component of fracture and decreases the critical brittle point.     

Gradient interpenetrating polymer networks

The methods of synthesis and properties of gradient interpenetrating polymer networks (IPN) are discussed based on literature and authors' own experimental data. Gradient IPN can be treated as a sequence of an infinite number of layers of IPNs, whose composition and properties vary gradually from the surface to the core of specimens. These are analysed the most important properties of gradient IPNs: temperature transitions, thermodynamic and physico-mechanical characteristics and the main direction of practical application of gradient IPN-based materials.     

Conference key distribution schemes for secure digital mobilecommunications

We propose a new service for digital mobile communication systems. The service enables two or more users to hold a secure conference. Two requirements must be considered: privacy and authentication. Privacy involves ensuring that an eavesdropper cannot intercept the conversations of the parties holding the conference. Authentication involves ensuring that service is not obtained fraudulently in order to avoid usage charges. We present two new conference key distribution schemes for digital mobile communication systems. In these schemes, a group of users can generate a common secret keg over a public channel so that they may hold a secure conference     

生物降解塑料开发现状与发展趋势

本文简要介绍国内外生物降解塑料的现状与发展趋势。