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Current Fluctuations (current + fluctuation)
Selected AbstractsTuning of electron transport through molecular bridge systems: A study of shot noiseINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2008Santanu K. Maiti Abstract We study electron transport characteristics through a single phenalenyl molecule attached with two nonsuperconducting electrodes by the use of Green's function technique. Parametric calculations are given based on the tight-binding model to characterize the electron transport through such molecular bridge system. It is observed that the electron transport properties are significantly influenced by (a) the interference effect and (b) the molecule-to-electrodes coupling strength. In this context we also describe the noise power of the current fluctuations that provides an important information about the electron correlation, which is obtained by calculating the Fano factor (F). The knowledge of this current fluctuations gives a key idea for fabrication of efficient molecular devices. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Excitation of millimeter-wave oscillations in InAlAs/InGaAs heterostructuresPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008S. Pérez Abstract We study the origin of strong Terahertz (THz) oscillations taking place in InAlAs/InGaAs slot diodes - base of High Electron Mobility Transistor (HEMT) devices - when bias surpasses 0.5 V. To this end we perform a microscopic analysis of current fluctuations, calculated by means of an ensemble Monte Carlo (MC) simulator. The millimeter and submillimeter waves are caused by the presence of Gunn-like oscillations whose dynamics is controlled by ballistic , valley electrons in the channel. These carriers are capable to reach extremely high velocities due to the influence of degeneracy effects (preventing scattering mechanisms) and the presence of a recessed geometry. The dependence of this process on the recess and recess-drain lengths is analyzed in order to improve the frequency and magnitude of the oscillations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mean electromotive force proportional to mean flow in MILD turbulenceASTRONOMISCHE NACHRICHTEN, Issue 1 2010K.-H. Rädler Abstract In mean-field magnetohydrodynamics the mean electromotive force due to velocity and magnetic-field fluctuations plays a crucial role. In general it consists of two parts, one independent of and another one proportional to the mean magnetic field. The first part may be nonzero only in the presence of mhd turbulence, maintained, e.g., by small-scale dynamo action. It corresponds to a battery, which lets a mean magnetic field grow from zero to a finite value. The second part, which covers, e.g., the , effect, is important for large-scale dynamos. Only a few examples of the aforementioned first part of the mean electromotive force have been discussed so far. It is shown that a mean electromotive force proportional to the mean fluid velocity, but independent of the mean magnetic field, may occur in an originally homogeneous isotropic mhd turbulence if there are nonzero correlations of velocity and electric current fluctuations or, what is equivalent, of vorticity and magnetic field fluctuations. This goes beyond the Yoshizawa effect, which consists in the occurrence of mean electromotive forces proportional to the mean vorticity or to the angular velocity defining the Coriolis force in a rotating frame and depends on the cross-helicity defined by the velocity and magnetic field fluctuations. Contributions to the mean electromotive force due to inhomogeneity of the turbulence are also considered. Possible consequences of the above findings for the generation of magnetic fields in cosmic bodies are discussed (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A study of the relation between current oscillations and pittingCHINESE JOURNAL OF CHEMISTRY, Issue 10 2003Hou-Yi Ma Abstract Anodic polarization behaviors of iron in pure H2SO4 and three mixed acidic solutions, H2SO4 + NaCl, H2SO4 + NaNO3 and H2SO4+ NaCl + NaNO3, were investigated. The potentiodynamic sweep curves showed that the current densities rose and dropped irregularly in H2SO4 + NaCl solution at the more anodic potentials since the iron surface suffered pitting attack in the solution, but the pitting corrosion was inhibited effectively in the presence of nitrate ions. The surface morphological measurements indicated that pits appeared on the iron surface in H2SO4 + NaCl solution and only a few unobvious corrosion spots were observed in H2SO4 + NaCl + NaNO3 solution after the iron electrode was potentiostatically polarized at 1.3 V. The oscillatory properties of iron are associated with the susceptibility of the iron to pitting. In H2SO4 + NaCl solution, the regular potentiostatic current oscillations gradually evolved into the irregular current fluctuations due to occurrence of the pitting; whereas in H2SO4 + NaCl + NaNO3 solution, the current oscillations took place regularly, like the oscillatory behavior in the pure H2SO4 solution. Thus, when the higher the oscillatory frequency, the more irregular oscillatory process and the more sensitive to pitting iron occurred. [source] | |||||||||||||