11,826 research outputs found
Normalised Root Mean Square and Amplitude of Sidebands of Vibration Response as Tools for Gearbox Diagnosis
Quick assessment of the condition of gearboxes used in helicopters is a safety requirement. One of the most widely used helicopter on-board-mounted condition monitoring system these days is the Health and Usage Monitoring System. It has been specifically designed to monitor the condition of all safety-critical components operating in the helicopter through calculation of so-called condition indicators (CIs) - signal processing routines designed to output a single number that represents the condition of the monitored component. Among number of available parameters, there is a couple of CIs that over the years of testing have earned a reputation of being the most reliable measures of the gear tooth condition. At the same time, however, it has been observed that in some cases, those techniques do not properly indicate the deteriorating condition with the propagation of a gear tooth fault with the period of operation. Hence, three more robust methods have been suggested, which are discussed in this article
Digital flight control research
The results of studies which were undertaken to contribute to the design of digital flight control systems, particularly for transport aircraft are presented. In addition to the overall design considerations for a digital flight control system, the following topics are discussed in detail: (1) aircraft attitude reference system design, (2) the digital computer configuration, (3) the design of a typical digital autopilot for transport aircraft, and (4) a hybrid flight simulator
Flavour equilibration in quark-gluon plasma
Within the framework of a dynamical and physically transparent model developed earlier, we study the time evolution of various quark flavours in the baryon-free region in ultrarelativistic heavy ion collisions. We show that even under optimistic conditions, the quark-gluon system fails to achieve chemical equilibrium
Dynamical order, disorder and propagating defects in homogeneous system of relaxation oscillators
Reaction-diffusion (RD) mechanisms in chemical and biological systems can
yield a variety of patterns that may be functionally important. We show that
diffusive coupling through the inactivating component in a generic model of
coupled relaxation oscillators give rise to a wide range of spatio-temporal
phenomena. Apart from analytically explaining the genesis of anti-phase
synchronization and spatially patterned oscillatory death regimes in the model
system, we report the existence of a chimera state, characterized by spatial
co-occurrence of patches with distinct dynamics. We also observe propagating
phase defects in both one- and two-dimensional media resembling persistent
structures in cellular automata, whose interactions may be used for computation
in RD systems.Comment: 6 pages, 4 figure
Behaviour of Magnetic Tubes in Neutron Star's Interior
It is found from Maxwell's equations that the magnetic field lines are good
analogues of relativistic strings. It is shown that the super-conducting
current in the neutron star's interior causes local rotation of magnetic flux
tubes carrying quantized flux.Comment: 6 pages, no figure
Characterization of the cyclic behavior of dry masonry joints
Dry masonry mechanics received little attention from research community, when compared with resources invested in traditional (mortar joint) masonry. Nevertheless, a large number of historical stone constructions use dry masonry joints, while, in constructions originally built with weak lime mortar, mortar deterioration leads to a behavior similar to dry masonry. Therefore, the objective of this paper is to contribute to the knowledge of the behavior of dry masonry joints under cyclic loading, which is a key aspect for seismic actions.
The work focuses on the characterization of Coulomb failure criterion and the load-displacement behavior of dry masonry joints under cyclic loading, including aspects as surface roughness, dilatancy and inelastic behavior. A displacement controlled test set-up using masonry couplets is used for this purpose. Besides providing a basis for understanding the behavior of masonry joints in tension, the experiments contribute also to the definition and parameterization of advanced non-linear numeric models
Persistence at the onset of spatiotemporal intermittency in coupled map lattices
We study persistence in coupled circle map lattices at the onset of
spatiotemporal intermittency, an onset which marks a continuous transition, in
the universality class of directed percolation, to a unique absorbing state. We
obtain a local persistence exponent of theta_l = 1.49 +- 0.02 at this
transition, a value which closely matches values for theta_l obtained in
stochastic models of directed percolation. This result constitutes suggestive
evidence for the universality of persistence exponents at the directed
percolation transition. Given that many experimental systems are modelled
accurately by coupled map lattices, experimental measurements of this
persistence exponent may be feasible.Comment: 7 pages, Latex, 6 Postscript figures, Europhysics Letters (to appear
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