Search results for " Spectra"
showing 10 items of 709 documents
Stochastic resonance in a tunnel diode in the presence of white or coloured noise
1995
We study the signal-to-noise ratio, signal and noise output levels in a fast bistable electronic system: a tunnel diode. We observe stochastic resonance when the system is driven by a sum of a small periodic signal and noise. The phenomenon is investigated for values of the driving frequency as high as 10 kHz. This is the highest frequency value used in SR experiments until now. In the presence of «white noise», we observe a nonmonotonic behavior characterized by a sharp dip in the output noise level measured at 100Hz and 1 kHz. A similar behavior is predicated by recent theories. We also present preliminary experimental results of SR in the presence of an Ornstein-Uhlenbeck noise. For the …
Frequency influence on the hot-electron noise reduction in GaAs operating under periodic signals
2008
A Monte Carlo study of the role of the frequency on the hot-electron intrinsic noise reduction in an n-type GaAs bulk driven by two mixed cyclostationary electric fields is presented. Previous numerical results showed the possibility to reduce the diffusion noise under specific wave-mixing conditions. In this work the variations of the noise properties are investigated by computing and integrating the spectral density of the velocity fluctuations. We found that the effect of reduction of the noise level due to the addition of a second field at twice frequency is almost independent of the frequency.
Computer-Aided Simultaneous Determination of Noise and Gain Parameters of Microwave Transistors
1979
A new method for the determination of noise and gain parameters of microwave linear two-ports (transistors) is presented. The method allows the simultaneous determination of the two parameter sets through a proper computer-aided procedure which processes the experimental data obtained from a measuring system employing noise meters and generators only. Experimental verifications carried-out on a microwave low noise transistor in S-band are reported.
On the noise resistance of field-effect transistors at microwave frequencies
2001
This paper presents a survey on the topical aspects of the noise resistance in field-effect transistors (FET) at microwave frequencies. Such noise parameter represents the sensitivity of the device noise figure to the departure from the minimum noise condition and is therefore important in all low-noise applications. The performance of the noise resistance in FETs has been reviewed since the first noise modeling analysis of short-gate devices were presented in the early '70s. The authors also comment and compare their own results on this subject as obtained by extensive experimental activity in the field of noisy device characterization vs. frequency, bias and temperature conditions.
Comment on "Highly nonlinear, sign-varying shift of hydrogen spectral lines in dense plasmas".
2004
The shift of hydrogen and hydrogenlike spectral lines in dense plasmas, calculated with the full computer simulation method, in nonquenching, classical path, dipole approximation for plasma-emitter interaction, is equal to zero. In the paper commented on, Escarguel et al., Phys. Rev. E 62, 2667 (2000) the electron concentrations ${N}_{e}$ and the corresponding temperature values T are shown to have been determined incorrectly.
Spectroscopy of the neutron-deficient nuclide 171Pt
2003
A number of previously unobserved gamma-rays emitted from the neutron-deficient nuclide Pt-171 have been identified using the recoil decay tagging technique. The level scheme has been updated using ...
Rare decay η→ππγγ in chiral perturbation theory
1996
We investigate the rare radiative {eta} decay modes {eta}{r_arrow}{pi}{sup +}{pi}{sup {minus}}{gamma}{gamma} and {eta}{r_arrow}{pi}{sup 0}{pi}{sup 0}{gamma}{gamma} within the framework of chiral perturbation theory at {ital O}({ital p}{sup 4}). We present photon spectra and partial decay rates for both processes as well as a Dalitz contour plot for the charged decay. {copyright} {ital 1996 The American Physical Society.}
Intruder features in the island of inversion: The case of33Mg
2001
The Na-33 beta decay was studied online using mass separation techniques and a first description of the level structure of the neutron-rich isotope Mg-33, with N=21, has been obtained. The experiment involved the measurement of beta-gamma, beta-gamma-gamma, and beta -n-gamma coincidences as well as neutron spectra by time-of-flight technique. The first low energy level scheme for the daughter nucleus Mg-33 is given with five bound states. Spin and parity assignments are proposed according to beta feedings and gamma -ray multipolarities, beta -strength distribution is evaluated, taking into account 1n- and 2n-emission channels and it is compared with the calculated GT strength distribution. …
Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry
2014
The magnetic dipole moments and changes in mean-square charge radii of the neutron-rich $^{218m,219,229,231}\text{Fr}$ isotopes were measured with the newly-installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at ISOLDE, CERN, probing the $7s~^{2}S_{1/2}$ to $8p~^{2}P_{3/2}$ atomic transition. The $\delta\langle r^{2}\rangle^{A,221}$ values for $^{218m,219}\text{Fr}$ and $^{229,231}\text{Fr}$ follow the observed increasing slope of the charge radii beyond $N~=~126$. The charge radii odd-even staggering in this neutron-rich region is discussed, showing that $^{220}\text{Fr}$ has a weakly inverted odd-even staggering while $^{228}\text{Fr}$ has normal staggering. This sugges…
Effect of the non-gaussianity on the measurement error for the filtered 1/f noise intensity
1999
To study the nature of the 1/f noise phenomenon in conductors, we seek a tool for testing different hypotheses of 1/f noise origin. The method analyzing the noise intensity at the output of a bandpass filter is discussed for the case of non-Gaussian processes. Data on measurement error are presented for the 1/f noise intensity in GaAs films and the Gaussian white noise emulated by a computer. A numerical model of 1/f noise as the superposition of telegraph random processes has been created. This method requires further improvement to check the noise for stationarity. Some ideas of how to do that are proposed.