Search results for "Transient"

A Perturbative Approach to Continuous-Time Quantum Error Correction

2014

We present a novel discussion of the continuous-time quantum error correction introduced by Paz and Zurek in 1998 [Paz and Zurek, Proc. R. Soc. A 454, 355 (1998)]. We study the general Lindbladian which describes the effects of both noise and error correction in the weak-noise (or strong-correction) regime through a perturbative expansion. We use this tool to derive quantitative aspects of the continuous-time dynamics both in general and through two illustrative examples: the 3-qubit and the 5-qubit stabilizer codes, which can be independently solved by analytical and numerical methods and then used as benchmarks for the perturbative approach. The perturbatively accessible time frame featur…

Characterization of the global network of optical magnetometers to search for exotic physics (GNOME)

2018

The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a network of geographically separated, time-synchronized, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. The GNOME is sensitive to nuclear- and electron-spin couplings to exotic fields from astrophysical sources such as compact dark-matter objects (for example, axion stars and domain walls). Properties of the GNOME sensors such as sensitivity, bandwidth, and noise characteristics are studied in the present work, and features of the network's operation (e.g., data acquisition, format, storage, and diagnostics) are described. Charac…

Timing and spectral changes of the Be X-ray transient EXO 0531-6609.2 through high and low state

2004

We report on spectral and timing analysis of BeppoSAX data of the 13.6 s period transient X-ray pulsar EXO 0531-6609.2. Observations were carried out in March 1997 and October 1998, catching the source during a high and a low emission state, respectively. Correspondingly, the X-ray luminosity is found at a level of 4.2x10^37 erg/s and 1.5x10^36 erg/s in the two states. In the high state the X-ray emission in the energy range 1-100 keV is well fitted by an absorbed power-law with photon index Gamma ~1.7 plus a blackbody component with a characteristic temperature of ~3.5 keV. Moreover, we find an evidence of an iron emission at ~6.8 keV, typical feature in this class of sources but never rev…

A 3D Meshless Approach for Transient Electromagnetic PDEs

2012

A full wave three dimensional meshless approach for electromagnetic transient simulations is presented. The smoothed particle hydrodynamic (SPH) method is used by considering the particles as interpolation points, arbitrarily placed in the computational domain. Maxwell’s equations in time domain with the assigned boundary and initial conditions are numerically solved by means of the proposed method. The computational tool is assessed and, for the first time, a 3D test problem is simulated in order to validate the proposed approach.

INFLUENCE OF UNCERTAINTIES ON PD TUNING

2013

The aim of this work is to present a method for tuning the parameters of PD controller under the influences of the uncertainties, in order to stabilize the position of a rotor supported by active magnetic bearings (AMBs). The uncertainties are relative to mass, transverse and polar moment of inertia of the rotor. The introduction of the uncertainties is due to an incomplete modeled dynamic of the system or in the case the system being subjected to a parametric variation. The presence of the uncertainties produces a set of differences among the values of the output. Poles displacement method is used to reach the asymptotically stability condition characterized by a periodic oscillation durin…

Detection of Radiated EM Transients by Exploiting Compact Spherical Antenna Features

2011

In this paper, the features of a compact spherical antenna, already efficiently used for ultra wide band applications, are investigated by exploiting the possibility of detecting electromagnetic transients with frequency content up to the very high frequency range. Transient phenomena with the above mentioned frequency content are those encountered, for example, in partial discharge detection. The behaviour of the adopted compact spherical antenna enables to successfully detect the waveform of typical partial discharge transient radiated electromagnetic field, so preserving the information necessary for the subsequent pattern analysis, typically carried out by using classical conducted meas…

Discovery of the optical counterpart to the CGRO transient GRO J1008 - 57

1994

Discovery of the optical counterpart to the ASCA transient AX 1845.0 - 0433

1996

Transient Reversible Growth and Percolation During Phase Separation

1988

Binary mixtures when quenched into the two-phase region exhibit transient percolation phenomena. These transient percolation phenomena and the underlying mechanism of transient reversible growth are investigated. In particular, one of the possible dynamical percolation lines between the dynamical spinodal and the line of macroscopic percolation is traced out. Analyzing the finite size effects with the usual scaling theory one finds exponents which seem to be inconsistent with the universality class of percolation. However, at zero temperature, where the growth is non-reversible and the transition of a sol-gel type, the exponents are consistent with those of random percolation.

Detecting Eccentricity and Demagnetization Fault of Permanent Magnet Synchronous Generators in Transient State

2019

Eccentricity and demagnetization fault of a four-pole 1.5 kW surface mounted permanent-magnet synchronous-generator (PMSG) were modelled by using time-discretised finite element analysis (FEA). Both fault types are caused by magnetic asymmetry in the generator. The faulty behaviour of a PMSG under transient operating condition is studied with FEA. Two search coils were wound around stator teeth on opposite sides of the rotor. The induced voltage from these coils will be equal in healthy case. A fault is detected when the induced voltages are non-identical. The simulation results revealed that the envelope of the induced search coil voltage had sinusoids during dynamic eccentricity and demag…