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On asymmetric periodic solutions in relay feedback systems
2021
Abstract Asymmetric self-excited periodic motions or periodic solutions which are produced by relay feedback systems that have symmetric characteristics are studied in the paper. Two different mechanisms of producing an asymmetric oscillation by a system with symmetric properties are noted and analyzed by the locus of a perturbed relay system (LPRS) method. Bifurcation between the ability to excite symmetric and asymmetric oscillation with variation of system parameters is analyzed. An algorithm of finding asymmetric solutions is proposed.
Numerical values of MnZn ferrite nonlinear susceptibilities in a lossless approximation
2017
On the basis of expressions for nonlinear magnetic susceptibilities of soft ferrites obtained earlier the analysis of phase shifts between components of flux density on different frequencies and the magnetic field strength is carried out. Only the largest nonlinear susceptibilities those of third and fifth order are considered. It is shown that in the frequency range where losses are small and can be neglected the susceptibility of third order is negative but that of fifth order is positive. These statements allow explaining the shape of output voltage of toroidal transformer with soft ferrite core induced by strong harmonic field strength in the input. Numerical values of nonlinear suscept…
Calculation of the electrostatic field in a dielectric-loaded waveguide due to an arbitrary charge distribution on the dielectric layer
2016
The goal of this paper is to study the electrostatic field due to an arbitrary charge distribution on a dielectric layer in a dielectric-loaded rectangular waveguide. In order to obtain this electrostatic field, the potential due to a point charge on the dielectric layer is solved in advance. The high computational complexity of this problem requires the use of different numerical integration techniques (e.g., Filon, Gauss-Kronrod, Lobatto, …) and interpolation methods. Using the principle of superposition, the potential due to an arbitrary charge distribution on a dielectric layer is obtained by adding the individual contribution of each point charge. Finally, a numerical differentiation o…
Using of reflections for expansion of frequency tuning in a THz-band gyrotron
2017
Effect of delayed reflection on operation of a second-harmonic THz-band gyrotron is studied. Theoretical analysis, numerical calculations and experimental observations for the 0.394 THz FU CW IIB gyrotron are presented.
An Energy Saving Mechanism Based on Vacation Queuing Theory in Data Center Networks
2018
To satisfy the growing need for computing resources, data centers consume a huge amount of power which raises serious concerns regarding the scale of the energy consumption and wastage. One of the important reasons for such energy wastage relates to the redundancies. Redundancies are defined as the backup routing paths and unneeded active ports implemented for the sake of load balancing and fault tolerance. The energy loss may also be caused by the random nature of incoming packets forcing nodes to stay powered on all the times to await for incoming tasks. This paper proposes a re-architecturing of network devices to address energy wastage issue by consolidating the traffic arriving from di…
Simplified feedback control system for scanning tunneling microscopy
2021
A Scanning Tunneling Microscope (STM) is one of the most important scanning probe tools available to study and manipulate matter at the nanoscale. In a STM, a tip is scanned on top of a surface with a separation of a few \AA. Often, the tunneling current between tip and sample is maintained constant by modifying the distance between the tip apex and the surface through a feedback mechanism acting on a piezoelectric transducer. This produces very detailed images of the electronic properties of the surface. The feedback mechanism is nearly always made using a digital processing circuit separate from the user computer. Here we discuss another approach, using a computer and data acquisition thr…
ZnMgO-based UV photodiodes: a comparison of films grown by spray pyrolysis and MBE
2016
Detecting the UV part of the spectrum is fundamental for a wide range of applications where ZnMgO has the potential to play a central role. The shortest achievable wavelength is a function of the Mg content in the films, which in turn is dependent on the growth technique. Moreover, increasing Mg contents lead to an electrical compensation of the films, which directly affects the responsivity of the photodetectors. In addition, the metal-semiconductor interface and the presence of grain boundaries have a direct impact on the responsivity through different gain mechanisms. In this work, we review the development of ZnMgO UV Schottky photodiodes using molecular beam epitaxy and spray pyrolysis…
Optical properties and microstructure of 2.02-3.30 eV ZnCdO nanowires: effect of thermal annealing
2013
International audience; ZnCdO nanowires with up to 45% Cd are demonstrated showing room temperature photoluminescence (PL) down to 2.02 eV and a radiative efficiency similar to that of ZnO nanowires. Analysis of the microstructure in individual nanowires confirms the presence of a single wurtzite phase even at the highest Cd contents, with a homogeneous distribution of Cd both in the longitudinal and transverse directions. Thermal annealing at 550 C yields an overall improvement of the PL, which is blue-shifted as a result of the homogeneous decrease of Cd throughout the nanowire, but the single wurtzite structure is fully maintained.
Real-time signal processing in embedded systems
2016
International audience
High-pressure x-ray-absorption study of GaSe
2002
The III-VI layered semiconductor InSe has been studied by high-pressure single crystal x-ray absorption spectroscopy up to a maximum pressure of 14 GPa. The In-Se distance has been measured in both the low- pressure layered phase and the high-pressure NaCl phase. The bond compressibility in the layered phase is lower than the ``a'' crystallographic parameter compressibility, which implies an increase of the angle between the In-Se bond and the layer plane. Under plausible hypothesis, a description of the evolution of the whole structure with pressure is given. In particular, the intralayer distance is observed to increase with increasing pressure. A plausible precursor defect and a simple m…