Failure of the tail rotor of the Mi-24 helicopter as a result of a long-term impact of spatial resonance coupling

The most important element that has an impact on the safety of flight includes the helicopter power plant and the transmission shaft assembly. Monitoring with the use of the traditional vibroacoustic techniques does not provide satisfactory results. It is especially difficult to detect spatial resonance couplings, which may result in dangerous and rapid breaking of elements. This article focuses on a specific mechanism for formation and deepening of resonance and effects of resonance couplings of two subassemblies. For their monitoring, the FAM-C method was applied. It uses an on-board generator as a sensor. This is a synchronous method, which enables one to detect the onset of spatial resonance.

IMPROVEMENT POTENTIAL FOR SOUND INSULATION OF SINGLE- AND MULTILAYER WALL PANELS

Relevance: Acoustic comfort in residential, public and industrial buildings. Existing types of wall panels often do not provide the required noise control.Purpose: Investigation of the improvement potential for sound insulation of single- and multi-layer wall panels having finitegeometric dimensions with diffuse sound lowering. Design/methodology/approach: Consideration of the sound propagation through the wall panel based on the theory of selfcoordination of wave fields developed by the Prof. Sedov‟s scientific school.Research findings: Analytical equations for calculating the limiting sound insulation of the wall panels determined by the inertial sound propagation. The improvement potential for sound insulation of single- and multi-layer wall panels having finite dimensions. Comparison of theoretical and xperimental results. It is shown that single- and multi-layer wall panels of finite geometric dimensions have improvement potential for sound insulation, which is determined by the ratio between their own and limiting sound insulation.Practical implications: Wall panel design must take into account the improvement potential for sound insulation. The sound insulation of wall panels is improved without increasing their mass and thickness. This is of great importance for design solutions for wall panels of civil and industrial buildings.Originality/value: The proposed method shows good agreement between experimental data and theoretical calculations. The improvement potential for sound insulation at the frequency level locates near the resonant frequencies, namely: near-boundary frequency of the full spatial resonance for single-layer wall panels; near-resonant frequency of the mass-elasticity-mass panels and near-boundary frequency of the full spatial resonance for multilayer wall panels and panel linings, respectively.

Numerical analysis on formation and transition of white-eye square superlattice patterns in dielectric barrier discharge system

The mechanism of formation and transformation of white-eye square patterns in dielectric barrier discharge system is investigated numerically, using the two-layer Lengyel–Epstein model with asymmetric and symmetric coupling. When the scale of the simulation system [Formula: see text] is two to three times of pattern wavelength [Formula: see text], it is found that an obvious intermediate state with square distribution appears by adjusting the ratio of diffusion coefficients [Formula: see text]/[Formula: see text]. When it is coupled with a suitable short-wavelength Turing mode in the range of [Formula: see text] to [Formula: see text], a new spatial resonance structure can be formed in the short-wavelength mode subsystem, and the pattern evolves from a simple square pattern to a white-eye square pattern. Although the two coupling methods achieve the same results, the duration time of the white-eye square pattern in the symmetric coupling method is significantly longer than that in the asymmetric coupling method. Because the quadratic coefficient of the amplitude equation in the reaction–diffusion system is not zero, the simple square pattern of the long wavelength mode subsystem gradually transits into a stable hexagon pattern gradually. As a result, the white-eye pattern transits from a square to a hexagon.

NICOLA LEFANU (b. 1947)But Stars Remaining (1970)

This chapter discusses a very early work by Nicola Lefanu, But Stars Remaining. This song highlights the composer’s flair and professionalism, revealing a keen awareness of practical issues and of the concerns of the performer. The piece has clear notation, with careful attention to detailed interpretative niceties. Although written originally for soprano, the work could also suit a flexible tenor. The composer envisages it being sung spontaneously, as from a high rock, with echoes reverberating, so there are plenty of gaps in the music to allow for spatial resonance. There are a good many innovative vocal devices and gestures for the singer to get used to, and the composer has annotated these meticulously. Conventional notation is mostly employed, apart from a few freer passages, where note-stems are absent.

Пространственный фотоотклик, формфактор и требования к голографическим материалам

Reviewed the problems arising during the recording of holograms in bulk media, which manifest themselves in the first queue as the spatial resonance of the hologram recording field with refractive index inhomogeneities due to the already recorded part of the holographic lattice. And secondly, as a cross-interaction of two nonlinearities at recording holograms - nonlinearity of diffraction efficiency and nonlinearity of field distribution holograms of exposure and visibility of a registered holographic lattice. It is noted that the appearance one more nonlinearity - the nonlinear photoresponse of the holographic material - for certain conditions leads not to a decrease in diffraction efficiency, but to its increase. The main classes of volume holographic media — dynamic media that form a photoresponse during the exposure without chemical treatment and with chemical treatment — are determined. The maximum achievable diffraction efficiencies for both types materials are shown. Recommendations are made to eliminate the undesirable consequences of the detected effects, based on the analysis of the basic laws of photoresponse formation taking into account spatial resonance and the presence of a formfactor.

Fashioned in the light of physics: the scope and methods of Halford Mackinder's geography

Throughout his career the geographer, and first reader in the ‘new’ geography at the University of Oxford, Halford Mackinder (1861–1947) described his discipline as a branch of physics. This essay explores this feature of Mackinder's thought and presents the connections between him and the Royal Institution professor of natural philosophy John Tyndall (1820–1893). My reframing of Mackinder's geography demonstrates that the academic professionalization of geography owed as much to the methods and instruments of popular natural philosophy and physics as it did to theories of Darwinian natural selection. In tracing the parallels between Tyndall and Mackinder, and their shared emphasis upon the technology of the magic lantern and the imagination as tools of scientific investigation and education, the article elucidates their common pedagogical practices. Mackinder's disciplinary vision was expressed in practices of visualization, and in metaphors inspired by physics, to audiences of geographers and geography teachers in the early twentieth century. Together, these features of Mackinder's geography demonstrate his role as a popularizer of science and extend the temporal and spatial resonance of Tyndall's natural philosophy.