Oligoorganogermanes: interplay between aryl and trimethylsilyl substituents

Derivatives of main group elements containing element–element bonds are characterized by unique properties due to -conjugation, which is an attractive subject for investigation. A novel series of digermanes, Ar3Ge-Ge(SiMe3)3, containing aryl (Ar = p-C6H4Me (1), p-C6H4F (2), C6F5 (3)) and trimethylsilyl substituents, was synthesized by the reaction of germyl potassium salt, [(Me3Si)3GeK*THF], with triarylchlorogermanes, Ar3GeCl. The optical and electronic properties of such substituted oligoorganogermanes were investigated spectroscopically by UV/vis absorption spectroscopy and theoretically by DFT calculations. The molecular structures of compounds 1 and 2 were studied by XRD analysis. Conjugation between all structural fragments (Ge-Ge, Ge-Si, Ge-Ar, where Ar is an electron-donating or withdrawing group) was found to affect the properties

Logistic potential of the supply chain: theoretical aspect

The article discusses such concepts as "logistics potential" and "supply chain". Their definitions, given by various authors have been studied. On the basis of the analysis the new concept which is "potential logistics supply chain" has been formulated

Reshoring: the Nature and Causes of Appearance

The paper studies reshoring, the reasons of its appearance. Besides the possible influence of the reshoring on international trade and international logistics is noted

Reshoring: the Nature and Causes of Appearance

The paper studies reshoring, the reasons of its appearance. Besides the possible influence of the reshoring on international trade and international logistics is noted

Research of material flow within the economic assessment of the supply chain of chemical products in the region

In the article we offer the order of material flow research which is carried out within the framework of economic assessment of a supply chain. The offered order is approbated on the example of the supply chain of chemical products in Vitebsk region

Logistic potential of the supply chain: theoretical aspect

The article discusses such concepts as "logistics potential" and "supply chain". Their definitions, given by various authors have been studied. On the basis of the analysis the new concept which is "potential logistics supply chain" has been formulated

Prospects for cooling of marine organisms with the ice using chitosan and its polyelectrolyte complexes

A new cooling medium for storage of fish and seafood is proposed - frozen water solution of polysaccharides of natural origin, as the natural biopolymer chitosan. Rational concentration of its solution for producing the chitosan ice is determined experimentally. Organoleptic, physical, and microbiological parameters of the ice prepared from solution of polyelectrolyte complexes of chitosan and its co-polymers are examined. Better results for cooling of marine raw materials are shown for the solution of polyelectrolyte complexes based on chitosan with sodium alginate and carboxymethyl cellulose. The chitosan-alginate ice is distinguished by higher density and homogeneous consistency within the temperature range from -5 to +5оC. Antiseptic microbiological activity of the chitosan-alginate ice is in 2.3 times higher as compared with the water ice and in 1.8 times higher than for the chitosan ice. High technological properties of the ice of polyelectrolyte complexes of chitosan with sodium alginate provide good prospects for its using in technology of cooling in fishery industry

ОЦЕНКА ВИБРАЦИИ ПУТИ ПРИ ВЫСОКИХ СКОРОСТЯХ ДВИЖЕНИЯ

This article proposes an analytical method of assessment of track’s vibration level, based on the spectral decomposition of functions of sleeper deflections under the influence of passing axles of rolling stock. Train is considered to be formed from vehicles of the same type and of unlimited length. Vibrations are studied within a stable system of coordinated, related to the ground, for one sleeper during the passage of a train of unlimited length through track’s cross section. The computational scheme takes into account vibration damping of a track, considered as an infinitely long beam on a viscoelastic foundation. The algorithm and the results of numerical calculation of track’s vibration are given at speeds in the area of conventionally critical speed (the speed at which the model that does not take into account energy dissipation on the way predicts vibrations of unrestricted amplitude).It is shown that when the train’s speed is equal to conditionally critical (of about 500–600 km / h), the track’s vibrations reach their peak in the whole frequency range. Results are obtained for a wide frequency range from 16 to 32000 Hz in 12 octave bands in decibel scale. Methods, outlined in this article, make it possible to solve problems of accumulation of residual track’s deformations, as well as give direction for solving problems associated with the vibrations of the roadbed.Авторами предложен аналитический метод оценки уровня вибрации пути и, в частности, виброускорений шпалы при прохождении поезда со скоростями свыше 500 км/ч. В расчетной схеме учтено демпфирование пути как бесконечной балки на упругом основании. Приведены алгоритм и результаты численного расчета вибраций при скоростях движения экипажа в зоне условно-критической скорости (когда в модели, не учитывающей рассеяния энергии в пути, прогнозируется возникновение колебаний неограниченно большой амплитуды). Показано, что при движении поезда со скоростью, равной условно-критической – порядка 500-600 км/ч, вибрации достигают максимума во всем частотном диапазоне. Решения получены для широкого спектра частот от 16 до 32000 Гц в двенадцати октавных полосах в децибельной шкале