Determination of tribosystem elements condition by the acoustic emission method

Викладено методологічні основи вибору методу для дослідження й контролю стану елементів трибосистеми без її зупинки і розбирання. Показано ефективність застосування методу акустичної емісії для дослідження динаміки фізико-хімічних процесів у тонких поверхневих шарах матеріалів при терті. Представлено методику, яка дозволяє проводити дослідження процесів тертя та зношування матеріалів із використанням методу акустичної емісії й судити про стан трибосистеми у будь-який момент часу її функціонування, тобто отримувати кількісну оцінку інтенсивності зношування матеріалу за значенням ентропійного параметра, а за параметром стану трибосистеми визначати момент виникнення мікропошкоджень у поверхневих шарах матеріалів, що труться, а це свідчить про перехід трибосистеми від нормального до патологічного виду зношування.In article are represented methodological bases of a choice of the method for research and control of tribosystem elements condition without its stop and sorting out. The efficiency of application of the acoustic emission method for research of dynamics of physical and chemical processes in surface layers of materials at friction is shown. The represented method allows to determine: significance of the wear intensity of a material in dependence on entropical parameter; the moment of transition of the tribosystem from normal to pathological appearance of wear in dependence on condition parameter of the tribosystem

Обработка сигналов домен-акустическим процессором в автокорреляционном режиме

Аналізується відношення сигнал/шум, яке може бути досягнуте під час оброблення сигналів домен-акустичним процесором. Показано, що якість обробки сигналів вказаним методом в ідеальному випадку визначається якістю цих первинних сигналів, при цьому за умови, що сигнал запису формується малошумним по- тужним генератором, то в автокореляцiйному режимі опорний сигнал формується із сигналу, який підлягає обробціIt is analyzed the signal / noise ratio, which can be achieved by the signal processing domain-acoustic processor. It is shown that the quality of signal processing by this method ideally determined by the quality of the primary signals. Provided that the recorded signal is formed by a powerful generator of low-noise, the autocorrelation mode, the reference signal generated from the signal, which is to be processedАнализируется отношение сигнал/шум, которое может быть достигнуто при обработки сигналов домен-акустическим процессором. Показано, что качество обработки сигналов указанным методом в идеальном случае определяется качеством этих первичных сигналов. При условии, что сигнал записи формируется малошумным мощным генератором, в автокорреляционном режиме опорный сигнал формируется из сигнала, который подлежит обработк

Adaptive forecasting and financial risk estimation

The study is directed towards development of an adaptive decision support system for modeling and forecasting nonlinear nonstationary processes in economy, finances and other areas of human activities. The structure and parameter adaptation procedures for the regression and probabilistic models are proposed as well as the respective information system architecture and functional layout are developed. The system development is based on the system analysis principles such as adaptive model structure estimation, optimization of model parameter estimation procedures, identification and taking into consideration of possible uncertainties met in the process of data processing and mathematical model development. The uncertainties are inherent to data collecting, model constructing and forecasting procedures and play a role of negative influence factors to the information system computational procedures. Reduction of their influence is favourable for enhancing the quality of intermediate and final results of computations. The illustrative examples of practical application of the system developed proving the system functionality are provided

Theory of periodic swarming of bacteria: application to Proteus mirabilis

The periodic swarming of bacteria is one of the simplest examples for pattern formation produced by the self-organized collective behavior of a large number of organisms. In the spectacular colonies of Proteus mirabilis (the most common species exhibiting this type of growth) a series of concentric rings are developed as the bacteria multiply and swarm following a scenario periodically repeating itself. We have developed a theoretical description for this process in order to get a deeper insight into some of the typical processes governing the phenomena in systems of many interacting living units. All of our theoretical results are in excellent quantitative agreement with the complete set of available observations.Comment: 11 pages, 8 figure

Education, knowledge, and symbolic form

This article aims to introduce Ernst Cassirer, and his philosophy of symbolic form, to education studies, and, in doing so, to challenge the widespread but deeply flawed views of knowledge and so-called knowledge-based education that have shaped recent education policy in England. After sketching the current educational landscape, and then some of the main lines of flight in Cassirer’s work, time is given to a comparison with Heidegger—a more familiar figure by far in Anglophone philosophy than Cassirer, and who contributed to the displacement of Cassirer—in order to illustrate more clearly Cassirer’s original contribution, in particular to the relationship between knowledge and time. Cassirer’s view of knowledge stands in marked and critical contrast to that which has shaped recent educational reform in England, as he sees knowledge as a productive and expressive matter, and repudiates what I call the ‘building-blocks’ picture of knowledge and the hierarchisation of subject areas

Bacterial Surface Appendages Strongly Impact Nanomechanical and Electrokinetic Properties of Escherichia coli Cells Subjected to Osmotic Stress

The physicochemical properties and dynamics of bacterial envelope, play a major role in bacterial activity. In this study, the morphological, nanomechanical and electrohydrodynamic properties of Escherichia coli K-12 mutant cells were thoroughly investigated as a function of bulk medium ionic strength using atomic force microscopy (AFM) and electrokinetics (electrophoresis). Bacteria were differing according to genetic alterations controlling the production of different surface appendages (short and rigid Ag43 adhesins, longer and more flexible type 1 fimbriae and F pilus). From the analysis of the spatially resolved force curves, it is shown that cells elasticity and turgor pressure are not only depending on bulk salt concentration but also on the presence/absence and nature of surface appendage. In 1 mM KNO3, cells without appendages or cells surrounded by Ag43 exhibit large Young moduli and turgor pressures (∼700–900 kPa and ∼100–300 kPa respectively). Under similar ionic strength condition, a dramatic ∼50% to ∼70% decrease of these nanomechanical parameters was evidenced for cells with appendages. Qualitatively, such dependence of nanomechanical behavior on surface organization remains when increasing medium salt content to 100 mM, even though, quantitatively, differences are marked to a much smaller extent. Additionally, for a given surface appendage, the magnitude of the nanomechanical parameters decreases significantly when increasing bulk salt concentration. This effect is ascribed to a bacterial exoosmotic water loss resulting in a combined contraction of bacterial cytoplasm together with an electrostatically-driven shrinkage of the surface appendages. The former process is demonstrated upon AFM analysis, while the latter, inaccessible upon AFM imaging, is inferred from electrophoretic data interpreted according to advanced soft particle electrokinetic theory. Altogether, AFM and electrokinetic results clearly demonstrate the intimate relationship between structure/flexibility and charge of bacterial envelope and propensity of bacterium and surface appendages to contract under hypertonic conditions