Occupational exposure of physical therapists to electric and magnetic fields and the efficacy of Faraday cages

Objective. Measure physical therapists' exposure to the electric and magnetic fields produced by 17 shortwave diathermy devices in physical therapy clinics in the city of Presidente Prudente, São Paulo State, Brazil. Compare the observed values with the exposure levels recommended by the International Commission on Non-ionizing Radiation Protection (ICNIRP). Observe the efficacy of Faraday cages as a means of protecting physical therapists from exposure to oscillating electric and magnetic fields.Methods. Electric and magnetic field measurements were taken at four points during actual physical therapy sessions: in proximity to the operator's pelvis and head, the devices' electrical cables, and the electrodes. The measuring equipment was a Wandel & Goltermann EMR-200.Results. The values obtained in proximity to the electrodes and cables were 10 to 30 times higher than ICNIRP's recommended occupational reference levels. In the shortwave diathermy treatment rooms with Faraday cages, the fields were even higher than in treatment rooms not so equipped-principally the magnetic field, where the values were more than 100 times higher than the ICNIRP exposure limit.Conclusions. The electric and magnetic field intensities obtained in this study are generally above the exposure levels recommend in ICNIRP standards. It was also observed that the Faraday cage offers physical therapists no protection, and instead, increases their level of exposure.

The CMS experiment at the CERN LHC

The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 10(34)cm(-2)s(-1) (10(27)cm(-2)s(-1)). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4 pi solid angle. Forward sampling calorimeters extend the pseudo-rapidity coverage to high values (vertical bar eta vertical bar <= 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.

On an Optimal Linear Control Applied to a Non-Ideal Load Transportation System, Modeled with Periodic Coefficients

In this paper, a load transportation system in platforms or suspended by cables is considered. It is a monorail device and is modelled as an inverted pendulum built on a car driven by a DC motor. The governing equations of motion were derived via Lagrange's equations. In the mathematical model we consider the interaction between the DC motor and the dynamical system, that is, we have a so-called non-ideal periodic problem. The problem is analysed and we also developed an optimal linear control design to stabilize the problem.

Nonlinear Dynamics and Control of an Ideal/Nonideal Load Transportation System With Periodic Coefficients

In this paper, a loads transportation system in platforms or suspended by cables is considered. It is a monorail device and is modeled as an inverted pendulum built on a car driven by a dc motor the governing equations of motion were derived via Lagrange's equations. In the mathematical model we consider the interaction between the dc motor and the dynamical system, that is, we have a so called nonideal periodic problem. The problem is analyzed, qualitatively, through the comparison of the stability diagrams, numerically obtained, for several motor torque constants. Furthermore, we also analyze the problem quantitatively using the Floquet multipliers technique. Finally, we devise a control for the studied nonideal problem. The method that was used for analysis and control of this nonideal periodic system is based on the Chebyshev polynomial exponsion, the Picard iterative method, and the Lyapunov-Floquet transformation (L-F transformation). We call it Sinha's theory.

On a control of a non-ideal mono-rail system with periodics coefficients

In this work, the problem in the loads transport (in platforms or suspended by cables) it is considered. The system in subject is composed for mono-rail system and was modeled through the system: inverted pendulum, car and motor and the movement equations were obtained through the Lagrange equations. In the model, was considered the interaction among of the motor and system dynamics for several potencies motor, that is, the case studied is denominated a non-ideal periodic problem. The non-ideal periodic problem dynamics was analyzed, qualitatively, through the comparison of the stability diagrams, numerically obtained, for several motor torque constants. Furthermore, one was made it analyzes quantitative of the problem through the analysis of the Floquet multipliers. Finally, the non-ideal problem was controlled. The method that was used for analysis and control of non-ideal periodic systems is based on the Chebyshev polynomial expansion, in the Picard iterative method and in the Lyapunov-Floquet transformation (L-F trans formation). This method was presented recently in [3-9].

Stochastic field processes in the mathematical modelling of damped transmission line vibrations

Wind-excited vibrations in the frequency range of 10 to 50 Hz due to vortex shedding often cause fatigue failures in the cables of overhead transmission lines. Damping devices, such as the Stockbridge dampers, have been in use for a long time for supressing these vibrations. The dampers are conveniently modelled by means of their driving point impedance, measured in the lab over the frequency range under consideration. The cables can be modelled as strings with additional small bending stiffness. The main problem in modelling the vibrations does however lay in the aerodynamic forces, which usually are approximated by the forces acting on a rigid cylinder in planar flow. In the present paper, the wind forces are represented by stochastic processes with arbitrary crosscorrelation in space; the case of a Kármán vortex street on a rigid cylinder in planar flow is contained as a limit case in this approach. The authors believe that this new view of the problem may yield useful results, particularly also concerning the reliability of the lines and the probability of fatigue damages. © 1987.

Dielectric and viscoelastic properties of cross-linked polyethylene aged under multi stressing conditions

Different measurements were performed in cross-linked polyethylene (XLPE) employed as insulating material in coaxial cables that were field-aged and laboratory-aged under multi-stressing conditions at room temperature. Samples were peeled from the XLPE cable insulation in three different positions: just below the external semiconductor layer (outer layer), in the middle (middle layer) and just above the internal semiconductor layer of the cable (inner layer). The imaginary part of the electric susceptibility showed three peaks that obey the Dissado-Hill model. For laboratory-aged XLPE samples peeled from the inner and from the middle positions the peak at very low frequency region increased while in samples from the outer position a quasi-DC conduction process was observed. In medium frequency range a broadening of the peak was observed for all samples. Viscoelastic properties determined through dynamic mechanical analysis suggested that the aging generates processes that promoted changes of the crystallinity and the cross-linking degrees of the polymer. Fourier transform infrared spectroscopy (FTIR) measurements revealed an increase of oxidation products (esters), evidence of polar residues of the bow-tie tree and the presence of cross-linking by-products (acetophenone). Optical and scanning electronic microscope (SEM) measurements in aged samples revealed the existence of voids and bow-tie trees that were formed during aging in the middle region of the cable.

Behavior of the PMD coefficient of optical links under influence of mechanical and thermal effects

This papers presents results on the variation of the PMD coefficient of optical links under influence of mechanical tests, such as tensile strength, bending and compression, and also during the application of a thermal cycle. Results revealed that the link coefficient is more influenced by the application of a tension load and also suffers significant variation under strong temperature changes. Copyrigth © SBMO.

Dielectric behavior of XLPE aged under multi-stressing conditions

In this work fresh cables were laboratory aged under multi-stressing conditions at room temperature. Foils were peeled from cables, with approximately 150 ?m thickness, from the outer, middle and inner positions of the XLPE cable insulating layer. For samples obtained from the outer cable layer position, an increasing near-permanent electrical conduction process with aging time was observed. At the middle and inner cable layer positions a flat-loss relaxation process was observed becoming a dominating process on the ageing. In addition, PEA results confirmed that degradation in the outer region of the XLPE cables arises from the simultaneous presence of dipoles and injected space charge that distorts the internal electric field on the ageing.

Location of single line-to-ground faults on distribution feeders using voltage measurements

This paper proposes a dedicated algorithm for lation of single line-to-ground faults in distribution systems. The proposed algorithm uses voltage and current phasors measured at the substation level, voltage magnitudes measured at some buses of the feeder, a database containing electrical, operational and topological parameters of the distribution networks, and fault simulation. Voltage measurements can be obtained using power quality devices already installed on the feeders or using voltage measurement devices dedicated for fault location. Using the proposed algorithm, likely faulted points that are located on feeder laterals geographically far from the actual faulted point are excluded from the results. Assessment of the algorithm efficiency was carried out using a 238 buses real-life distribution feeder. The results show that the proposed algorithm is robust for performing fast and efficient fault location for sustained single line-to-ground faults requiring less than 5% of the feeder buses to be covered by voltage measurement devices. © 2006 IEEE.

Electrical devices obtained from polymeric precursors process

Nowadays, many investments have been made in the area of superconductor materials, with the aim to improve their potential technological applications. Applications on the energy transport using cables, to get high resolution images in the medicine use high magnetic fields, high speed signals use superconductor devices all of them are in crescent evidence and they are showing that the future is coming and next for this new kind of materials. Obviously that everything of this is possible due to the increasing of research with new materials, where the synthesis, characterization and applications are of the mainly objective of these researches. The production of cable for the energy transport has been in advanced stage as the bulks production is too. However, the film production that to aim at the electronic devices area is not as developed or it still need expensive investments. Thinking about that, we are developing a research where we may increase the relation of cost/benefits. Thereby, we are applying the polymeric precursors method to obtain films that will be used in the built of electronic devices. Thin films (mono and multilayers, on crystalline or metallic substrates, controlled thickness) of the BSCCO system have been obtained from dip coating deposition process with excellent results in terms of preferential orientation, controlled thickness, a large area, which may indicate future applications. Based on these results, we present an electrical circuit and their principal characteristics as superconductor transition (85K), transport current density and structure. DC four probes method, scanning electron microscopy, digital optical microscopy and X-ray diffractometry were some techniques used for the characterization of this superconductor electric device. © 2006 Materials Research Society.

Utilização de redes neurais recorrentes na caracterização de cargas não lineares em sistemas elétricos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Metodologia de localização de defeitos em redes subterrâneas integrando PSCAD/EMTDC e sistemas inteligentes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise do suporte de reativos em um sistema elétrico de potência com link HVDC

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação da suscetibilidade eletromagnética dos cabos metálicos dos sistemas de supervisão, proteção, comunicação e controle de subestações de alta tensão

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)