6,226 research outputs found
The use of a simplified structural model as an aid in the strain gage calibration of a complex wing
The use of a relatively simple structural model to characterize the load responses of strain gages located on various spars of a delta wing is examined. Strains measured during a laboratory load calibration of a wing structure are compared with calculations obtained from a simplified structural analysis model. Calculated and measured influence coefficient plots that show the shear, bending, and torsion characteristics of typical strain gage bridges are presented. Typical influence coefficient plots are shown for several load equations to illustrate the derivation of the equations from the component strain gage bridges. A relatively simple structural model was found to be effective in predicting the general nature of strain distributions and influence coefficient plots. The analytical processes are shown to be an aid in obtaining a good load calibration. The analytical processes cannot, however, be used in lieu of an actual load calibration of an aircraft wing
Ballistic Electron Quantum Transport in Presence of a Disordered Background
Effect of a complicated many-body environment is analyzed on the electron
random scattering by a 2D mesoscopic open ballistic structure. A new mechanism
of decoherence is proposed. The temperature of the environment is supposed to
be zero whereas the energy of the incoming particle can be close to or
somewhat above the Fermi surface in the environment. The single-particle
doorway resonance states excited in the structure via external channels are
damped not only because of escape through such channels but also due to the
ulterior population of the long-lived environmental states. Transmission of an
electron with a given incoming through the structure turns out to be
an incoherent sum of the flow formed by the interfering damped doorway
resonances and the retarded flow of the particles re-emitted into the structure
by the environment. Though the number of the particles is conserved in each
individual event of transmission, there exists a probability that some part of
the electron's energy can be absorbed due to environmental many-body effects.
In such a case the electron can disappear from the resonance energy interval
and elude observation at the fixed transmission energy thus resulting
in seeming loss of particles, violation of the time reversal symmetry and, as a
consequence, suppression of the weak localization. The both decoherence and
absorption phenomena are treated within the framework of a unit microscopic
model based on the general theory of the resonance scattering. All the effects
discussed are controlled by the only parameter: the spreading width of the
doorway resonances, that uniquely determines the decoherence rateComment: 7 pages, 1 figure. The published version. A figure has been added;
the list of references has been improved. Some explanatory remarks have been
include
An Investigation of Coach Behaviors, Goal Motives, and Implementation Intentions as Predictors of Well-Being in Sport
The present study aimed to expand upon Smith, Ntoumanis, and Duda’s (2007) research by investigating the influence of coach behaviors and implementation intentions on goal striving in sport. Structural equation modeling analysis with a sample of 108 athletes revealed coach behaviors as predictors of goal motives, which in turn predicted psychological well-being after 8 weeks. Supplementary regression analyses showed no interaction between autonomous goal motives and implementation intentions; however, a synergistic effect was identified for controlled goal motives such that controlled motives furnished with implementation intentions resulted in lower well-being than controlled motives alone. In further analyses, the motives underlying an implementation intention were found to mediate the paths from goal motives to well-being. The findings are discussed in terms of the roles played by goal motives, implementation intentions, and implementation intention motives during goal striving
Dirac Point and Edge States in a Microwave Realization of Tight-Binding Graphene-like Structures
We present a microwave realization of finite tight-binding graphene-like
structures. The structures are realized using discs with a high index of
refraction. The discs are placed on a metallic surface while a second surface
is adjusted atop the discs, such that the waves coupling the discs in the air
are evanescent, leading to the tight-binding behavior. In reflection
measurements the Dirac point and a linear increase close to the Dirac point is
observed, if the measurement is performed inside the sample. Resonances due to
edge states are found close to the Dirac point if the measurements are
performed at the zigzag-edge or at the corner in case of a broken benzene ring.Comment: 4 pages, 6 figure
1D quantum models with correlated disorder vs. classical oscillators with coloured noise
We perform an analytical study of the correspondence between a classical
oscillator with frequency perturbed by a coloured noise and the one-dimensional
Anderson-type model with correlated diagonal disorder. It is rigorously shown
that localisation of electronic states in the quantum model corresponds to
exponential divergence of nearby trajectories of the classical random
oscillator. We discuss the relation between the localisation length for the
quantum model and the rate of energy growth for the stochastic oscillator.
Finally, we examine the problem of electron transmission through a finite
disordered barrier by considering the evolution of the classical oscillator.Comment: 23 pages, LaTeX fil
Two-Dimensional Magnetic Resonance Tomographic Microscopy using Ferromagnetic Probes
We introduce the concept of computerized tomographic microscopy in magnetic
resonance imaging using the magnetic fields and field gradients from a
ferromagnetic probe. We investigate a configuration where a two-dimensional
sample is under the influence of a large static polarizing field, a small
perpendicular radio-frequency field, and a magnetic field from a ferromagnetic
sphere. We demonstrate that, despite the non-uniform and non-linear nature of
the fields from a microscopic magnetic sphere, the concepts of computerized
tomography can be applied to obtain proper image reconstruction from the
original spectral data by sequentially varying the relative sample-sphere
angular orientation. The analysis shows that the recent proposal for atomic
resolution magnetic resonance imaging of discrete periodic crystal lattice
planes using ferromagnetic probes can also be extended to two-dimensional
imaging of non-crystalline samples with resolution ranging from micrometer to
Angstrom scales.Comment: 9 pages, 11 figure
On the theory of cavities with point-like perturbations. Part I: General theory
The theoretical interpretation of measurements of "wavefunctions" and spectra
in electromagnetic cavities excited by antennas is considered. Assuming that
the characteristic wavelength of the field inside the cavity is much larger
than the radius of the antenna, we describe antennas as "point-like
perturbations". This approach strongly simplifies the problem reducing the
whole information on the antenna to four effective constants. In the framework
of this approach we overcame the divergency of series of the phenomenological
scattering theory and justify assumptions lying at the heart of "wavefunction
measurements". This selfconsistent approach allowed us to go beyond the
one-pole approximation, in particular, to treat the experiments with
degenerated states. The central idea of the approach is to introduce
``renormalized'' Green function, which contains the information on boundary
reflections and has no singularity inside the cavity.Comment: 23 pages, 6 figure
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Ignition of Aluminum Particles and Clouds
Here we review experimental data and models of the ignition of aluminum (Al) particles and clouds in explosion fields. The review considers: (i) ignition temperatures measured for single Al particles in torch experiments; (ii) thermal explosion models of the ignition of single Al particles; and (iii) the unsteady ignition Al particles clouds in reflected shock environments. These are used to develop an empirical ignition model appropriate for numerical simulations of Al particle combustion in shock dispersed fuel explosions
Tailoring Anderson localization by disorder correlations in 1D speckle potentials
We study Anderson localization of single particles in continuous, correlated,
one-dimensional disordered potentials. We show that tailored correlations can
completely change the energy-dependence of the localization length. By
considering two suitable models of disorder, we explicitly show that disorder
correlations can lead to a nonmonotonic behavior of the localization length
versus energy. Numerical calculations performed within the transfer-matrix
approach and analytical calculations performed within the phase formalism up to
order three show excellent agreement and demonstrate the effect. We finally
show how the nonmonotonic behavior of the localization length with energy can
be observed using expanding ultracold-atom gases
Anderson localization as a parametric instability of the linear kicked oscillator
We rigorously analyse the correspondence between the one-dimensional standard
Anderson model and a related classical system, the `kicked oscillator' with
noisy frequency. We show that the Anderson localization corresponds to a
parametric instability of the oscillator, with the localization length
determined by an increment of the exponential growth of the energy. Analytical
expression for a weak disorder is obtained, which is valid both inside the
energy band and at the band edge.Comment: 7 pages, Revtex, no figures, submitted to Phys. Rev.
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