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Authors would like to acknowledge the support provided by Federal University of Par? (UFPA), for all infrastructure provided.

Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in high-voltage apparatus. Partial discharges are a source of failure in power transformers, and the differentiation from other sources of acoustic emissions is of the utmost importance. This paper reports the development of a new sensor concept-mandrel-based fiber-optic sensor-for the detection of incipient faults in oil-filled power transformers, taking direct measurements inside a transformer. These sensors can be placed in the inner surface of the transformer tank wall, not affecting the insulation integrity of the structure, and improving fault detection and location. The applicability of these acoustic sensors in air, water, and oil is investigated and the paper presents the promising results obtained, which will enable the industrial development of practical solutions.

This article reports the development of two sensing head configurations based on extrinsic and intrinsic fiber Fabry-Perot interferometers for the detection of incipient faults in oil-filled power transformers. The performances of the sensing heads are characterized and compared with the situations where it operates in air, water, and oil and promising results are obtained, which will allow the industrial development of practical solutions. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1129–1134, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25139

This work describes a educational tool developed in Java language for simulating a multi-static radar. This radar is used to identify the presence of an intruder inside a residence. In order to obtain high resolution, the radar operates with ultra-wideband pulses (Gaussian monocycle), which have maximum spectral amplitude at 1 GHz and half power bandwidth of approximately 1 GHz. For the estimation of the intruder's position, the optimization technique particle swarm optimization (PSO) is employed. The simulator allows that the users define the parameters to be used by the radar and obtain the estimation of the intruder's position. Besides that, the software automatically generates animations of the wave propagation inside the residence, graphics of the signal at the receiving points and a final report with all the information related to the simulations.

The finite-difference time-domain (FDTD) technique is applied to the analysis of planar dielectric waveguides controlled by means of an optical beam. This beam, with an appropriate energy, induces a nonuniform plasma in a semiconductor layer deposited on the waveguide core. The resulting effects are analyzed through the phase dispersion characteristics. Due to the complexity of the problem, the FDTD formulation does not allow the calculation of the attenuation characteristic, particularly when the plasma presents an intermediate density, which causes a strong interaction with the guided mode. The simulations shown here suggest that the light beam may have an effective control of the phase response of a single waveguide and of the coupling between two parallel coupled waveguides.

The finite-difference time-domain (FDTD) method is used for the analysis of magnetoplasma rectangular channel waveguides. Single and parallel-coupled waveguides are considered. The effect of varying the amplitude and the orientation of the bias magnetic field B/sub 0/ on the dispersion characteristics of the first modes is examined. However, the FDTD formulation, does not excite evanescent modes for a sufficiently long time interval, particularly when in the presence of the propagating or dynamic modes. As a result, the nonreciprocal properties of these structures, primarily associated with the evanescent modes, could not be investigated.

Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in the high voltage apparatus. Partial discharges are a major source of insulation failure in electric power transformers, and the differentiation from other sources of acoustic emission is of the utmost importance. This paper reports the development of a new sensor concept — a fiber laser sensor based on a phase-shifted chirped fiber grating — for the acoustic emission detection of incipient faults in oil-filled power transformers. These sensors can be placed in the inner surface of the transformer tank wall, not affecting the insulation integrity of the structure and improving fault detection and location. The performance of the sensing head is characterized and compared for different surrounding media: air, water, and oil. The results obtained indicate the feasibility of this sensing approach for the industrial development of practical solutions.

Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in high voltage apparatus. Partial discharges are a major source of insulation failure in power transformers and the differentiation from other sources of acoustic emissions is of the utmost importance. Also, it is important to give an indication of the PD source location in order to obtain a useful diagnosis. This paper reports the developments in partial discharges source location through the associated acoustic emissions using three different algorithms.

Partial discharges are a major source of insulation failure in electric power transformers. Their detection can be achieved through the associated acoustic emissions, and this work reports on the investigation of a fibre laser sensor based on a phase-shifted chirped fibre grating for acoustic emission detection in the power transformer environment. The performance of the sensing head is characterized and compared for different surrounding media: air, water and oil.

Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in high voltage apparatus. A great number of methods are available for condition monitoring and diagnosis of power transformer insulation, but only a few can take direct measurements inside a transformer. Partial discharges are a major source of insulation failure in power transformers and their detection can be achieved through the associated acoustic emissions. This paper reports the development of two sensing head configurations based on extrinsic and intrinsic fiber Fabry-Perot interferometers for the detection of incipient faults in oil-filled power transformers. These sensors can be placed inside the transformer tank without affecting the insulation integrity, improving fault detection and location. The performances of the sensing heads are characterized and compared with the situations where it operates in air, water and oil and promising results are obtained, which will allow the industrial development of practical solutions.

A numeric simulation of a multistatic radar using the finite-difference time-domain (FDTD) method and particle swarm optimization (PSO) is implemented in order to localize an intruder inside a laboratory complex. In order to obtain high resolution and to avoid interference with other radiosystems, the radar operates with ultra-wideband pulses and spectral spreading. The transmitted signal has a spectral peak at 1 GHz and the bandwidth of approximately 1 GHz. To estimate the location of the target, two transmitters and nine receivers are used. The transmitters operate in TDM mode in order to avoid interference between them.

A simulation of a multistatic radar using the finite-difference time-domain method is performed to identify the presence of an intruder inside a residence. The radar operates with ultra-wideband pulses to obtain high resolution. One transmitter and three receivers, positioned outside the residence, are used to estimate the location of an intruder inside the residence without ambiguity.

A numeric simulation of a multistatic radar using the finite-difference time-domain (FDTD) method is implemented in order to identify the presence of an intruder inside a residence. The radar operates with ultra-wideband (UWB) pulses with the purpose of obtaining high resolution. The transmitted signal has a spectral peak in 1 GHz and the bandwidth of approximately 1 GHz. A transmitter and at least three receivers positioned outside the residence are used to estimate the location of the target without ambiguity. A special emphasis is given to study of the effects of scatterers placed in semi-aleatory way in all rooms of the residence. A strategy is proposed to minimize these effects in order to obtain complete coverage of the residence with small error of the intruder localization.

A finite-difference time domain (FDTD) method is developed for the analysis of the electromagnetic wave propagation in semiconductor waveguides containing a magnetostatic-field controlled plasma. Dispersion characteristic curves are obtained for a variety of waveguides. However, since the FDTD formulation developed cannot excite evanescent modes for a sufficiently long time, only the dynamic or propagating modes are excited. As a result, the desired non-reciprocal effects, associated with these modes could not be examined.

The formulation of the finite difference time domain method (FDTD) for the analysis of propagation characteristic of rectangular waveguides filled with magnetized plasma is presented here. In this formulation the FDTD method is used for the numerical solution of Maxwell's equations in the time domain. As a result, the system of partial differential equations formed by the electric and magnetic field components is replaced by a system of finite difference equations that are solved iteratively. The results presented show a variation of the dispersion characteristics of the structures examined as functions of the plasma parameters.

The finite-difference time domain (FDTD) method for dispersive media is applied to the study of the electromagnetic wave propagation in optically-controlled coupled-dielectric-waveguides. The optical control is achieved by means of light incidence on semiconductor layers deposited onto the waveguides. The effects produced by the induced plasma in the semiconductor are analyzed through the dispersion characteristic of the waveguide structure.

The finite-difference in the time-domain method for dispersive media ((FD)/sup 2/TD) is applied to study the wave propagation in optically-controlled dielectric waveguide. The optical control is done by means of plasma generation in a semiconductor layer deposited on the waveguide. The resulting effects on the electric field components of the E/sub 11//sup x/ and E/sub 11//sup y/ modes are shown by means of the waveguide dispersion characteristic curve.