A theoretical model of a wake of a body towed in a stratified fluid at large Reynolds and Froude numbers

International audienceThe objective of the present paper is to develop a theoretical model describing the evolution of a turbulent wake behind a towed sphere in a stably stratified fluid at large Froude and Reynolds numbers. The wake flow is considered as a quasi two-dimensional (2-D) turbulent jet flow whose dynamics is governed by the momentum transfer from the mean flow to a quasi-2-D sinuous mode growing due to hydrodynamic instability. The model employs a quasi-linear approximation to describe this momentum transfer. The model scaling coefficients are defined with the use of available experimental data, and the performance of the model is verified by comparison with the results of a direct numerical simulation of a 2-D turbulent jet flow. The model prediction for the temporal development of the wake axis mean velocity is found to be in good agreement with the experimental data obtained by Spedding (1997)

CAROTID CHEMODECTOMA: DIFFERENTIAL DIAGNOSIS ACCORDING TO ULTRASOUND DATA

Carotid chemodectoma (“chemodectoma caroticum”, a carotid glomus tumor) is a benign slow-growing, vascularized tumor that is one of the most common paragangliomas of the head and neck. The ultrasound examination of 18 000 patients referred for various reasons revealed 2 cases of carotid chemodectoma verified by angiography. The paper gives the current ideas of the rate, etiology, pathomorphology, and clinical manifestations of chemodectoma, as well as its major ultrasound differential diagnostic criteria

Modal testing circuit board assembly of an electronic apparatus by laser vibrometry

The operating capacity and service life of printed circuit boards in various electronic equipment and devices depends on their ability to resist vibroacoustic loads, including vibration and acoustic noises. In this paper, non-contact laser vibrometry has been applied to perform the modal analysis of a circuit board assembly in order to identify its vulnerable spots and to find solutions to protect the assembly from external vibroacoustic loads. A broadband periodic chirp signal was used to excite vibration, which enabled a rapid generation of results. The paper provides data on eigenfrequencies, vibration velocity fields, and vibration displacement profiles. Frequency ranges have been determined in which eigenfrequencies with the highest vibration amplification lie. The obtained data can be used to develop a quality control technique for printed circuit boards and to optimize their construction as early as the design stage

Axial anomaly and mixing: from real to highly virtual photons

The relation for transition form factors of eta and eta' mesons is obtained by combining the exact nonperturbative QCD sum rule, following from the dispersive representation of axial anomaly, and quark-hadron duality. It is valid at all virtual photon momenta and allows one to express the transition form factors entirely in terms of meson decay constants. This relation is in a good agreement with experimental data.Comment: 10 pages, 4 figures. Minor corrections, references added and updated; to appear in Phys.Rev.

Study of the e+e−→ηγe^+e^-\to\eta\gamma process with SND detector at the VEPP-2M e+e−e^+e^- collider

In experiment with the SND detector at VEPP-2M $e^+e^-$ collider the $e^+e^-\to\eta\gamma$ cross section was measured in the energy range $E$=0.60--1.38 GeV with the integrated luminosity of 27.8 pb$^{-1}$. The measured cross section is well described by the vector meson dominance model with contributions from the $\rho(770)$, $\omega(783)$, $\phi(1020)$, $\rho^{\prime}(1465)$ resonances and agrees with results of previous measurements. The decay probabilities \BR(\phi\to\eta\gamma), \BR(\omega\to\eta\gamma) and \BR(\rho\to\eta\gamma) were measured with the accuracies better than or comparable to the world averages.Comment: 13 pages, 6 figures, 5 table

Адаптивная информационно-управляющая система динамического мониторинга фактической обводненности авиатоплива в технологических процессах авиатопливообеспечения

Modern domestic and international standards, regulators of the aviation fuel industry, considering the negative impact of the presence of mechanical impurities and water in aviation fuel on the performance and life cycle of aircraft engines, fuel metering equipment, fuel systems of aircraft (A/C), as a threat factor for flight safety, impose high requirements for the purity of aviation fuel while operating aeronautical equipment. At the same time, the causes and sources of water content in jet fuel are a source of economic losses, the most important criterion for the success of the Aerodrome Fueling Complex business. The article considers the task of developing reliable and automated methods as well as technologies for controlling these contaminants, for example for determining water content in aviation fuel when refueling aircraft, and the necessity to minimize an effect of a human factor. The automation of aviation fuel quality monitoring processes, the transition from discrete control methods to continuous ones, from static control methods to dynamic ones (in-line), from indirect methods to direct ones are becoming relevant. The possibilities of end-to-end accounting and analysis of aviation fuel purity parameters at all stages of the aviation fuel life cycle are shown. The article considers the methods and conducts the analysis of known techniques and devices used to determine, measure and indicate actual water content, presence of dissolved, free and total water in jet fuel. The technical solution of continuous automated control of the actual water content level of the jet fuel flow in the processes of aviation fuel supply and aircraft refueling in an information system that provides on-line monitoring and dynamic measurement of the quantitative content of dissolved and free water in the jet fuel flow, is presented. The technical solution for the continuous determination of the quantitative water content in the jet fuel stream is proposed. At the same time, the solution of the problem of monitoring water content in jet fuel is combined with the technological process to control the purification of jet fuel from water. The paper represents an adaptive information management system for continuous monitoring of the water content level of the jet fuel flow, which will allow specialist to substantially increase a level of automatization of aircraft aviation fuel supply technological processes, decrease a negative impact of a human factor, increase economic effectiveness of the aviation fuel supply complex. The system is designed to carry out continuous, automated control (monitoring) of water content in the jet fuel flow at all the stages of the jet fuel movement: receiving, storing and delivering jet fuel and refueling aircraft, in particular fuel and lubricants warehouses (fuel and lubricants), refueling complexes and pre-apron filling points. It can also be used in the fuel system of the aircraft, as a system to prevent water content in the jet fuel. The integration of automation tools will enable us to improve the quality of management of aviation fuel supply and aircraft refueling to ensure timely operational decision based on real data in real time mode, provided the proposed system integration into the airport system for operational data exchange.Современные отечественные и международные требования регуляторов отрасли авиатопливообеспечения, принимая во внимание негативное влияние присутствия механических примесей и воды в авиатопливе на работоспособность и ресурс авиадвигателей, топливорегулирующей аппаратуры, топливных систем воздушных судов (ВС) как фактора угрозы безопасности полетов ВС, предъявляют к чистоте применяемого при эксплуатации авиационной техники авиатоплива высокие требования. Вместе с тем причины и источники обводнения авиатоплива являются источником экономических потерь, важнейшим критерием успешности бизнеса топливозаправочного комплекса. В статье рассматривается задача создания надежных и автоматизированных методов и технологий контроля этих загрязнений, в частности определения воды в авиатопливе при заправке ВС и необходимости ухода от человеческого фактора. Актуальным становится автоматизация процессов мониторинга качества авиатоплива, переход от дискретных методов контроля к непрерывным, от статических методов контроля к динамическим (поточным), от косвенных способов к прямым. Показаны возможности сквозного учета и анализапараметров чистоты авиатоплива на всех этапах жизненного цикла авиатоплива. Рассмотрены способы, и проведен анализ известных методов и устройств, используемых для определения, измерения и индикации: фактической обводненности; присутствия растворенной, свободной и суммарной воды в авиатопливе. Представлено техническое решение непрерывного автоматизированного контроля уровня фактической обводненности потока авиатоплива в процессах авиатопливообеспечения и заправки ВС в информационной системе, обеспечивающей on-line контроль и динамическое измерение количественного содержания растворенной и свободной воды в потоке авиатоплива. Предложено техническое решение по непрерывному определению количественного содержания воды в потоке авиатоплива. При этом решение задачи мониторинга воды в авиатопливе совмещено с технологическим процессом контроля очистки авиатоплива от воды. Представлена адаптивная информационно-управляющая система непрерывного мониторинга уровня обводненности авиатоплива в потоке, которая позволит существенно повысить уровень автоматизации технологических процессов авиатопливообеспечения воздушных судов, снизить негативное влияние человеческого фактора, повысить экономическую эффективность комплекса авиатопливообеспечения. Система предназначена для осуществления непрерывного автоматизированного контроля (мониторинга) обводненности авиатоплива в потоке на всех этапах движения авиатоплива: приема, хранения и выдачи авиатоплива, и заправки ВС, в частности складов горюче-смазочных материалов, топливозаправочных комплексов, и пунктов предперонного налива, а также может быть использована в топливной системе ВС как система предотвращения обводнения авиатоплива. Внедрение средств автоматизации позволит повысить качество управления процессами авиатопливообеспечения и заправки ВС для обеспечения принятия своевременных оперативных решений на основе реальных данных в реальном режиме времени при условии интеграции предложенной системы в систему аэропорта для оперативного обмена данными