10,706 research outputs found
Spacetime metric from linear electrodynamics
The Maxwell equations are formulated on an arbitrary (1+3)-dimensional
manifold. Then, imposing a (constrained) linear constitutive relation between
electromagnetic field and excitation , we derive
the metric of spacetime therefrom.Comment: 4 pages' latex-scrip
Density Matrix Renormalization Group for Dummies
We describe the Density Matrix Renormalization Group algorithms for time
dependent and time independent Hamiltonians. This paper is a brief but
comprehensive introduction to the subject for anyone willing to enter in the
field or write the program source code from scratch.Comment: 29 pages, 9 figures. Published version. An open source version of the
code can be found at http://qti.sns.it/dmrg/phome.htm
Auralization of Amplitude Modulated Helicopter Flyover Noise
Rotorcraft noise is an active field of study as the sound produced by these vehicles is often found to be annoying. A means to auralize rotorcraft flyover noise is sought to help understand the factors leading to annoyance. Previous work by the authors auralized a complete flyover event in which the source noise synthesis traversed a range of emission angles. The source noise definition process for the synthesis used helicopter flyover recordings. Although this process yielded both periodic and aperiodic (modulation) components at a set of discrete emission angles, only the periodic components were used in the previous work to synthesize the sound of the flyover event. In the current work, aperiodic amplitude modulation is incorporated into the source noise synthesis to improve its fidelity toward assessing rotorcraft noise annoyance. The method is demonstrated using ground recordings from a flight test of the AS350 helicopter for the source noise definition
Quantum Interference Effects in Spacetime of Slowly Rotating Compact Objects in Braneworld
The phase shift a neutron interferometer caused by the gravitational field
and the rotation of the earth is derived in a unified way from the standpoint
of general relativity. General relativistic quantum interference effects in the
slowly rotating braneworld as the Sagnac effect and phase shift effect of
interfering particle in neutron interferometer are considered. It was found
that in the case of the Sagnac effect the influence of brane parameter is
becoming important due to the fact that the angular velocity of the locally non
rotating observer must be larger than one in the Kerr space-time. In the case
of neutron interferometry it is found that due to the presence of the parameter
an additional term in the phase shift of interfering particle emerges
from the results of the recent experiments we have obtained upper limit for the
tidal charge as . Finally, as an example, we
apply the obtained results to the calculation of the (ultra-cold neutrons)
energy level modification in the braneworld.Comment: 12 pages, 2 figure
On the Use of Acoustic Wind Tunnel Data for the Simulation of sUAS Flyover Noise
Acoustic measurements of a small, unmanned aerial system were recently acquired during a ground test campaign. The purposes of the ground test, conducted in the NASA Langley Low Speed Aeroacoustic Wind Tunnel, were to characterize the source noise in terms of its tonal and broadband content, and to identify conditions under which multirotor and rotor-airframe interactions are present. The focus of this work is to assess the effectiveness of using those data for the simulation of flyover noise at a ground observer. The assessment is made at two levels of fidelity using different sets of tools. In the first, 1/3 octave band spectra at a ground receiver will be simulated in a frequency domain approach using the NASA Aircraft NOise Prediction Program. In the second, the pressure time history at a ground receiver is simulated in a time domain approach using the NASA Auralization Framework. Various objective measures are used to verify the simulation process. Acoustic wind tunnel and flight test data are used to gain insight into perceptually important effects
Amyloid Fibril Solubility
It is well established that amyloid fibril solubility is protein specific, but how solubility depends on the interactions between the fibril building blocks is not clear. Here we use a simple protein model and perform Monte Carlo simulations to directly measure the solubility of amyloid fibrils as a function of the interaction between the fibril building blocks. Our simulations confirms that the fibril solubility depends on the fibril thickness and that the relationship between the interactions and the solubility can be described by a simple analytical formula. The results presented in this study reveal general rules how side-chain–side-chain interactions, backbone hydrogen bonding, and temperature affect amyloid fibril solubility, which might prove to be a powerful tool to design protein fibrils with desired solubility and aggregation properties in general
Identifying through its decay modes
We study how to assign the recently observed meson to an
appropriate level of the spectrum by the analysis of its decay modes
in final states comprising a light pseudoscalar meson. We use an effective
lagrangian approach with heavy quark and chiral symmetries, obtaining that the
measurement of the decay width would allow to distinguish between two
possible assignments.Comment: RevTex, 6 pages - references adde
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