10,910 research outputs found
Current flight test experience related to structural divergence of forward-swept wings
Flight testing the X-29A forward-swept wing aircraft has required development of new flight test techniques to accomplish subcritical extrapolations to the actual structural divergence dynamic pressure of the aircraft. This paper provides current experience related to applying these techniques to analysis of flight data from the forward-swept wing in order to assess the applicability of these techniques to flight test data. The measurements required, maneuvers flown, and flight test conditions are described. Supporting analytical predictions for the techniques are described and the results using flight data are compared to these predictions. Use of the results during envelope expansion and the resulting modifications to the techniques are discussed. Some of the analysis challenges that occurred are addressed and some preliminary conclusions and recommendations are made relative to the usefulness of these techniques in the flight test environment
Intermittency as a universal characteristic of the complete chromosome DNA sequences of eukaryotes: From protozoa to human genomes
Large-scale dynamical properties of complete chromosome DNA sequences of
eukaryotes are considered. By the proposed deterministic models with
intermittency and symbolic dynamics we describe a wide spectrum of large-scale
patterns inherent in these sequences, such as segmental duplications, tandem
repeats, and other complex sequence structures. It is shown that the recently
discovered gene number balance on the strands is not of random nature, and a
complete chromosome DNA sequence exhibits the properties of deterministic
chaos.Comment: 4 pages, 5 figure
Incommensurate dynamics of resonant breathers in Josephson junction ladders
We present theoretical and experimental studies of resonant localized
resistive states in a Josephson junction ladder. These complex breather states
are obtained by tuning the breather frequency into the upper band of linear
electromagnetic oscillations of the ladder. Their prominent feature is the
appearance of resonant steps in the current-voltage (I-V) characteristics. We
have found the resonant breather-like states displaying incommensurate
dynamics. Numerical simulations show that these incommensurate resonant
breathers persist for very low values of damping. Qualitatively similar
incommensurate breather states are observed in experiments performed with
Nb-based Josephson ladders. We explain the appearance of these states with the
help of resonance-induced hysteresis features in the I-V dependence.Comment: 5 pages, 6 figure
Sublattice synchronization of chaotic networks with delayed couplings
Synchronization of chaotic units coupled by their time delayed variables are
investigated analytically. A new type of cooperative behavior is found:
sublattice synchronization. Although the units of one sublattice are not
directly coupled to each other, they completely synchronize without time delay.
The chaotic trajectories of different sublattices are only weakly correlated
but not related by generalized synchronization. Nevertheless, the trajectory of
one sublattice is predictable from the complete trajectory of the other one.
The spectra of Lyapunov exponents are calculated analytically in the limit of
infinite delay times, and phase diagrams are derived for different topologies
Tunable multi-photon Rabi oscillations in an electronic spin system
We report on multi-photon Rabi oscillations and controlled tuning of a
multi-level system at room temperature (S=5/2 for Mn2+:MgO) in and out of a
quasi-harmonic level configuration. The anisotropy is much smaller than the
Zeeman splittings, such as the six level scheme shows only a small deviation
from an equidistant diagram. This allows us to tune the spin dynamics by either
compensating the cubic anisotropy with a precise static field orientation, or
by microwave field intensity. Using the rotating frame approximation, the
experiments are very well explained by both an analytical model and a
generalized numerical model. The calculated multi-photon Rabi frequencies are
in excellent agreement with the experimental data
Superconducting coplanar waveguide resonators for low temperature pulsed electron spin resonance spectroscopy
We discuss the design and implementation of thin film superconducting
coplanar waveguide micro- resonators for pulsed ESR experiments. The
performance of the resonators with P doped Si epilayer samples is compared to
waveguide resonators under equivalent conditions. The high achievable filling
factor even for small sized samples and the relatively high Q-factor result in
a sensitivity that is superior to that of conventional waveguide resonators, in
particular to spins close to the sample surface. The peak microwave power is on
the order of a few microwatts, which is compatible with measurements at ultra
low temperatures. We also discuss the effect of the nonuniform microwave
magnetic field on the Hahn echo power dependence
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The influence of wake chopping on wet-steam turbine modelling
Abstract
The formation of water droplets within condensing steam turbines is a complex process that occurs at supersaturated, non-equilibrium conditions and is influenced by the unsteady segmentation of blade wakes by successive blade rows. This is often referred to as ‘wake chopping’, and its effect on the condensation process is the subject of this paper. The practical significance is that thermodynamic ‘wetness losses’ (which constitute a major fraction of the overall loss) are strongly affected by droplet size. Likewise, droplet deposition and the various ensuing two-phase phenomena (such as film migration and coarse-water formation) also depend on the spectrum of droplet sizes in the primary fog.
The majority of wake-chopping models presented in the literature adopt a stochastic approach, whereby large numbers of fluid particles are tracked through (some representation of) the turbine flowfield, assigning a random number at each successive blade row to represent the particle’s pitchwise location, and hence its level of dissipation. This study contributes to the existing literature by adding: (a) a comprehensive study of the sensitivity to key model parameters (e.g., blade wake shape and wake decay rate); (b) an assessment of the impact of circumferential pressure variations; (c) a study of the implications for wetness losses and (d) a study of the implications for deposition rates.General Electri
Control of gradient-driven instabilities using shear Alfv\'en beat waves
A new technique for manipulation and control of gradient-driven instabilities
through nonlinear interaction with Alfv\'en waves in a laboratory plasma is
presented. A narrow field-aligned density depletion is created in the Large
Plasma Device (LAPD), resulting in coherent unstable fluctuations on the
periphery of the depletion. Two independent kinetic Alfv\'en waves are launched
along the depletion at separate frequencies, creating a nonlinear beat-wave
response at or near the frequency of the original instability. When the
beat-wave has sufficient amplitude, the original unstable mode is suppressed,
leaving only the beat-wave response at a different frequency, generally at
lower amplitude.Comment: Submitted for Publication in Physical Review Letters. Revision 2
reflects changes suggested by referees for PRL submission. One figure
removed, several major changes to another figure, and a number of major and
minor changes to the tex
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