885 research outputs found
Mesoscopic Behavior Near a Two-Dimensional Metal-Insulator Transition
We study conductance fluctuations in a two-dimensional electron gas as a
function of chemical potential (or gate voltage) from the strongly insulating
to the metallic regime. Power spectra of the fluctuations decay with two
distinct exponents (1/v_l and 1/v_h). For conductivity , we find a third exponent (1/v_i) in the shortest samples, and
non-monotonic dependence of v_i and v_l on \sigma. We study the dependence of
v_i, v_l, v_h, and the variances of corresponding fluctuations on \sigma,
sample size, and temperature. The anomalies near
indicate that the dielectric response and screening length are critically
behaved, i.e. that Coulomb correlations dominate the physics.Comment: Revised according to referee remark
Line shifts in accretion disks - the case of Fe K
Here we present a short overview and main results of our investigations of
several effects which can induce shifts in the broad Fe K line emitted
from relativistic accretion disks around single and binary supermassive black
holes. We used numerical simulations based on ray-tracing method in the Kerr
metric to study the role of classical Doppler shift, special relativistic
transverse Doppler shift and Doppler beaming, general relativistic
gravitational redshift, and perturbations of the disk emissivity in the
formation of the observed Fe K line profiles. Besides, we also
investigated whether the observed line profiles from the binary systems of
supermassive black holes could be affected by the Doppler shifts due to
dynamics of such systems. The presented results demonstrate that all these
effects could have a significant influence on the observed profiles of the
broad Fe K line emitted from relativistic accretion disks around single
and binary supermassive black holes.Comment: 9 pages, 5 figures, 1 table. Accepted for publication in Astrophysics
and Space Scienc
Evidence for electron-phonon interaction in FeMSb (M=Co, Cr) single crystals
We have measured polarized Raman scattering spectra of the
FeCoSb and FeCrSb (00.5)
single crystals in the temperature range between 15 K and 300 K. The highest
energy symmetry mode shows significant line asymmetry due to phonon
mode coupling width electronic background. The coupling constant achieves the
highest value at about 40 K and after that it remains temperature independent.
Origin of additional mode broadening is pure anharmonic. Below 40 K the
coupling is drastically reduced, in agreement with transport properties
measurements. Alloying of FeSb with Co and Cr produces the B mode
narrowing, i.e. weakening of the electron-phonon interaction. In the case of
A symmetry modes we have found a significant mode mixing
Overview of modern contributions in vehicle noise and vibration refinement with special emphasis on diagnostics
U ovom radu prikazana su odreÄena razmatranja vezana za karakteristike buke i vibracija savremenih motornih vozila. Pored nauÄnog, problematika se razmatra i sa praktiÄnog aspekta u cilju struktuiranja potrebnih znanja, neophodnih za pravilnu dijagnostiku problema. TakoÄe se razmatraju napredne analize signala buke i vibracija. Ova sinergija nauÄnog i praktiÄnog pristupa predstavlja osnovu za dalja napredna istraživanja.This paper presents certain considerations related to noise, vibration and harshness issues on modern motor vehicles. The first, practical aspect was used toward structuring of the acquired knowledge and relationships, required for proper problem diagnosis. On the other hand, advanced signal analyses are considered. The influence on human body is processed and certain noise and vibration analyzers are presented. This synergy of scientific and applicative approach represents a basis for further research related to this important automotive branch
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