Physical mathematical bases of the principle of independence of cavity expansion

For the first steps of cavitation researches the very important general peculiarity of supercavitating flow was found which discovered practical independence of cavity sections expansion in motionless fluid. This peculiarity gave the possibility for practical estimation of the cavities in the most part of applications. The paper presents the system of the simple dependencies for practical calculations of axisymmeric and near to one supecavitation flows with account of its perfection on the base of modern achievements of the theoretic and experimental research which based on the property of independence of the cavity section expansion. Main attention is paid to asymptotic dependencies on the base of Slender Body Theory and heuristic models. The calculations examples of steady and unsteady cavities for motion under gravity, axelration, harmonic oscillation of pressure are given. The problems of ventilated cavities and possible ways of drag reduction for motion with supercavitation are considered.http://deepblue.lib.umich.edu/bitstream/2027.42/84216/1/CAV2009-final169.pd

High speed motion in water with supercavitation for sub-, trans-, supersonic Mach Numbers

The results of research for supercavitating motion in water at very high speeds comparable with sonic speed ~1500m/s are presented. At such speeds the water is a compressible fluid and the basic compressible hydrodynamics of supercavitating flows together with practical approaches and experimental data are considered. The theory of ballistic projectiles motion is developed with emphasis on the problems of maximal range, lateral motion prediction and problems of minimal declination, hydro-elastic effects, and resonant oscillation frequencies. One main purpose of the article is an attempt to advance the level of understanding of the problem of very high-speed underwater launch by a comprehensive review of previous research on this topic.http://deepblue.lib.umich.edu/bitstream/2027.42/84267/1/CAV2009-final72.pd

New designs of engines for drive of gas compressor units

Предложены новые конструктивные разработки электродвигателей мегаваттного класса для интегрированных исполнений агрегатов нефтегазовой отрасли. Проведен анализ основных преимуществ асинхронных и синхронных машин в электроприводах газоперекачивающих агрегатов. Рассмотрены особенности конструкций интегрированных электродвигателей с горизонтальной и вертикальной осями вращения. Показаны эффективные результаты реализации безредукторных и безмасляных технологий для повышения функциональных возможностей, надежности, энергоэффективности и экологичности наиболее ответственных электромеханических систем.New constructive developments of electric motors of megawatt class for the integrated executions of the units of oil and gas industry are offered. The analysis of the basic advantages of asynchronous and synchronous machines of electric drives of gas compressor units has been carried out. There considered the features of designs of the integrated electric motors with horizontal and vertical axes of rotation. The effective results of realization of gearless and oil free technologies for increase of functionality, reliability, power efficiency and ecological compatibility of the most essential electromechanical systems have been shown

Theory of the collapsing axisymmetric cavity

We investigate the collapse of an axisymmetric cavity or bubble inside a fluid of small viscosity, like water. Any effects of the gas inside the cavity as well as of the fluid viscosity are neglected. Using a slender-body description, we show that the minimum radius of the cavity scales like $h_0 \propto t'^{\alpha}$, where $t'$ is the time from collapse. The exponent $\alpha$ very slowly approaches a universal value according to $\alpha=1/2 + 1/(4\sqrt{-\ln(t')})$. Thus, as observed in a number of recent experiments, the scaling can easily be interpreted as evidence of a single non-trivial scaling exponent. Our predictions are confirmed by numerical simulations

Analysis of power characteristics of high-voltage frequency converters for speed control of turbocompressors

Представлен анализ особенностей топологии и энергетических характеристик современных высоковольтных преобразователей частоты для электроприводных компрессорных станций. Рассмотрены особенности схемных структур и функциональных возможностей многоуровневых преобразователей отечественного производства для повышения энергоэффективности и надежности электроприводов. Проведено моделирование гармонического состава выходного напряжения и тока высоковольтных преобразователей частоты и получены осциллограммы выходных характеристик и гармонические спектры параметров 5 наиболее типичных структур преобразователей частоты при работе на активно-индуктивную нагрузку. Представлены результаты расчета коэффициентов искажения выходного напряжения и тока и соответствующие уровни спектров частот.The analysis of the topology features and power characteristics of modern high-voltage converters of frequency is presented. The features of the circuit structures and the functional capabilities of multilevel converters of domestic production for power efficiency and reliability increase of electric drives have been considered. There conducted the simulation of a harmonic composition of output voltage and current of highvoltage converters of frequency and received the oscillograms of output characteristics and harmonious spectra of the parameters of 5 most typical structures of converters of frequency at the work for an active-inductive loading The results of calculation of the factors of distortion of output voltage and current and the corresponding levels of spectra of the frequencies have been presented

DIFFERENCES IN AGGRESSIVE BEHAVIOR OF RELATED SPECIES OF FLYCATCHERS (MUSCICAPIDAE) FAMILY

The article is devoted to the observation of differences in relation between aggressive behavior of related species of Flycatchers (Muscicapidae) family and behavior acts in naturally watering places. Observations have reviled the timing separation between presence and engagement of Flycatchers in morning hours and relation with acts of aggression. Each representative of Flycatchers family is using the watering place in different ways. The correlation between intraspecific and interspecific contacts with the predominance of interspecific and highly aggressive interactions has been analyzed. The rating of successfulness of the acts of aggression has been established for every particular group of Flycatchers. It demonstrates the energetic justification of aggressive behavior for spotter, red-breasted and pied flycatchers but energetic overspend and failure for collared flycatcher

Phenological Observations of Birds of the Chernobyl Exclusion Zone Settlements Before the Accident on Chernobyl Nuclear Power Station

У статі наведено результати фенологічних спостережень за 21 видом птахів у 1976–1985 роках, проведених на територіях, що згодом увійшли до Чорнобильської зони відчуження. Наведено перелік основних синантропних мігруючих птахів сіл, з яких після аварії на ЧАЕС було виселено людей. Виявлено тенденцію до зміщення термінів прильоту до більш ранніх. Вказано дані про чисельність колоніальних гніздувань граків у деяких населених пунктах до аварії на ЧАЕС. The article presents the results of phenological observations of 21 bird species in 1976–1985, which were hold on the territories, which later became part of the Chernobyl exclusion zone. Here is given the list of main synanthropic migratory birds of settlements, where people were later evacuated from. As it turned out, there is a tendency to removing arriving dates to the earlier ones. The data on the quantity of colonial rook settlements in some of populated localities before the accident are also given in the article.Роботу виконано на кафедрі зоології ННЦ «Інститут біології» КНУ ім. Т. Шевченк