42 research outputs found
Virtual load and substructure method in repetitive structures analysis by discrete Fourier transform
No full textOn static analysis of finite repetitive structures by discrete Fourier transform
No full textFunctional solutions for the static response of beam- and plate-like repetitive lattice structures are obtained by discrete Fourier transform. The governing equation is set up as a single operator form with the physical stiffness operator acting as a convolution sum and containing a matrix kernel, which relates to the mechanical properties of the lattice. Boundary conditions do not affect the equation form, and are taken into account at a subsequent stage of the analysis. The technique of virtual load and substructure is proposed to formally close the repetitive lattice into a cyclic structure, and to assure the equivalence of responses of the modified cyclic and original repetitive lattices. A discrete periodic Green's function is introduced for the modified structure, and the final displacement solutions are written as convolution sums over the Green's function and the actual external and virtual loads. Several example problems illustrate the approach
Characteristic solutions for the statics of repetitive beam-like trusses
No full textThis paper concerns two major points: (1) decomposition of functional solutions for the static response of repetitive pin-jointed beam trusses under end loadings into spectrum of elementary function modes; and (2) a mathematical classification of the last. The governing finite difference equation of statics is written as a single matrix form by considering the stiffness matrix of a representative substructure. It is shown that its general solution can be spanned by only 2R individual modes, where R is the number of degrees of freedom for a typical nodal pattern inside the truss. These modes are divided into two primary classes: transfer and localised. A unique set of "canonical" transfer solutions is found by a method based on Jordan decomposition of the transfer matrix. Also, a technique of constructing transfer matrices for a wide class of trusses is presented. The canonical modes can be further subclassified as exponential, polynomial and quasi-polynomial. The complete set of 2R canonical transfer and localised modes uniquely represents the basic structural response behaviour, and gives a basis for the characteristic (non-harmonic) expansion of static solutions. Several illustrative examples are considered
The Centenary of the Birth of Professor Georgy I. Dorofeev
No full textThe article is devoted to one of the leaders of the Leningrad school of gastroenterologists of the second half of the last century. For almost two decades, he headed the oldest department of the Military Medical Academy — the Department of Hospital Therapy, turning it into one of the famous gastroenterological centers of the country of that period. The author offers the reader the complete biography of this famous scientist. One of the most important scientific merits of G.I. Dorofeev is the creation of an original scientific internist school. Many followers of it headed and continue to head the leading scientific centers of the country
To the Question of Universal Electronic Cards’ Use in the Russian Federation
No full textThe author has carried out the work to identify gaps in legal regulation and problems of law enforcement practice in the sphere of public and municipal services provided via universal electronic card, as well as analysis of prospects for the use of electronic media as a comprehensive substitute of an identity card of the citizen of the Russian Federatio
Analysis of the Causes of long-Term Changes in Economic Inequality in the Global Economy
No full textThe author examines long-term changes in economic inequality in the global economy. The aim of the article is to update, analyze and systematize the long-term causes of changes in economic inequality in the global economy and identify its country specifics. The author used the methods of analysis and synthesis, systematization, classification and categorization of information from various scientific and statistical sources and databases. To illustrate the trends in economic inequality, the author applied the indicator of the share of national income among different groups of the population. The study revealed the cyclical nature of economic inequality in accordance with Kondratieff innovation waves lasting 50-60 years. Based on the data analysis of economic inequality for the period 1900-2018, the author concluded that technological progress is the priority factor in changing economic inequality. Together with the country specifics of the financial mechanism for redistributing income and wealth and various regimes of international cooperation and trade, it affects the changes in cross-country and domestic economic inequality. Understanding the nature of changes in inequality will allow for effective long-term strategies for economic development and the corresponding state regulation policy in the context of faster digitalization and robotization of the global economy
