Load torque estimation in induction motors using artificial neural networks

The induction motors are largely used in several industry sectors. The dimensioning of an induction motor has still been inaccurate because in most of the cases the load behavior in its shaft is completely unknown. The proposal of this paper is to use artificial neural networks as tool for dimensioning of induction motors rather than conventional methods, which use classical identification techniques and mechanical load modeling. Simulation results are also presented to validate the proposed approach.

Microstructure and corrosion resistance of inorganic-organic (ZrO2-PMMA) hybrid coating on stainless steel

Zirconia-polymethylmetacrylate hybrids prepared by a sol-gel method were deposited by dip-coating on stainless steel to improve the resistance against wet corrosion. The effect of the concentration of polymethylmetacrylate and the number of coating applications on the microstructure and corrosion performance of coated samples was investigated. The microstructural properties of samples was analyzed by scanning electron and atomic force microscopy, adhesion tests and profilemeter measurements. The electrochemical corrosion was evaluated through potentiodynamic polarization curves at room temperature. Results show that the sample prepared with 17 vol.% of polymethylmethacrylate has a maximum corrosion resistance, smaller roughness, are hermetic and adherent to the substrate. This film increases the life time of the stainless steel by a factor 30. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Poole-Frenkel effect in Er doped SnO2 thin films deposited by sol-gel-dip-coating

Electrical properties of Er-doped SnO2 thin films obtained by sol-gel-dip-coating technique were measured. When compared to undoped tin dioxide, rare-earth doped films present much higher resistivity, indicating that Er3+ presents an acceptor-like character into the matrix, which leads to a high degree of electric charge compensation. Current-voltage characteristics, measured above room temperature for Er-doped films, lead to non-linear behavior and two conduction regimes. In the lower electric field range the conduction is dominated by Schottky emission over the grain boundary potential barrier, which presents an average value of 0.85 eV. Increasing the applied bias, a second regime of conduction is observed, since the Poole-Frenkel coulombic barrier lowering becomes a significant effect. The obtained activation energy for ionization is 0.67 eV. (C) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structure of SnO2 alcosols and films prepared by sol-gel dip coating

To obtain SnO2 films to be used for surface protection of fluoride glasses, a non-aqueous sol-gel route for the preparation was developed. An ethanolic SnO2 colloidal suspension was prepared by thermohydrolysis of SnCl4 solution at 70 degreesC. By using this procedure, redispersable powders with nanometer sized particles were obtained. Films were obtained by dip coating on glass and mica substrates. The structures of the ethanolic precursor suspension and films were compared to those of similar samples prepared by the classical aqueous sol-gel route. Comparative analyses performed by photon correlation spectroscopy demonstrated that the powders obtained by freeze-drying are fully redispersable either in aqueous or in alcoholic solutions at pH greater than or equal to 8. As prepared sols and redispersed colloidal suspensions have hydrodynamic radius distribution (2-14 nm) with an average size close to 7 nm. The variations in film structures with firing temperature were investigated by small-angle X-ray scattering and X-ray reflectometry. The experimental results show that the films have a two level porous structure composed of agglomerates of primary colloidal particles. The sintering of the primary particles leads to the densification of agglomerates and to the formation of inter-agglomerate spatially correlated pores. The volume fraction of intra-agglomerate pores is reduced from approximate to 50% to approximate to 30% by the precipitation of precursor salts partially hydrolyzed in ethanolic solution. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Influence of heat treatment on the optical properties of SnO2 : Sb thin films deposited by dip coating using aqueous solution

Antimony doped tin oxide thin films were deposited on glass by a chemical route derived from Pechini method. Particular emphasis was given to the microstructure of crystallized films. Crystalline phase formation was studied by grazing incident X-ray diffraction and by thermal analyses. Scanning electron microscopy was carried out for microstructure characterization, surface roughness was observed using scanning tunneling microscope and the optical transmittance measurements were performed in the wavelength range of 200-800 nm. (C) 2002 Kluwer Academic Publishers.

Transparent and conductive ZnO : Al thin films prepared by sol-gel dip-coating

Aluminum doped zinc oxide polycrystalline thin films (AZO) were prepared by sol-gel dip-coating process. The sol was prepared from an ethanolic solution of zinc acetate using lithium hydroxide or succinic acid as hydrolytic catalyst. The quantity of aluminum in the sol was varied from 1 to 10 mol%. The structural characteristics studied by X-ray diffractometry were complemented by resistivity measurements and UV-Vis-NIR spectroscopy. The films are transparent from the near ultraviolet to the near infrared, presenting an absorption cut-off at almost 290 nm, irrespective of the nature of the catalyst and doping level. The best conductors were obtained for the AZO films containing 3 mol% of aluminum, prepared under acidic and basic catalysis and sintered at 450 degreesC. Their optical band-gap of 4.4 eV calculated from the absorption cut-off is larger than the values for band-gap widening predicted by the standard model for polar semiconductors. These polycrystalline films are textured with preferential orientation of grains along the wurtzite c-axis or the (100) direction. (C) 2003 Elsevier Ltd. All rights reserved.

Electromyographic study in Erector spinae, Rectus abdominis, Glutaeous maximus and Rectus femuris muscles, in standing and static posture with load on hands

Observe the loads associates application with in position of body, in the static or dynamic postures. Methods: the electromyographic study in erector spinae, rectus abdominis, glutaeous maximus and rectus femoris muscles was accomplished in female volunteers from 18 have 27 years old, previously selected. The muscles electric activities was gotten with surface electrodes, in standing and static posture, with the parallels and horizontal upper limbs with load on their hands. Conclusion: In this study it was clearly observed influence of the load and distance there is over studied musculature associated with standing erect posture.

Deposition of controlled thickness ultrathin SnO2 : Sb films by spin-coating

The technological interest in transparent conductive oxide films (TCOs) has motivated several works in processing techniques, in order to obtain adequate routes to application. In this way, this work describes a new route to obtain antimony-doped tin oxide (ATO) films, based in colloidal dispersions of oxide nanocrystals. The nanoparticles were obtained by a hydrolisis method, using SnCl2 and SbCl3 in ethanolic solutions. The residual halides were removed by dyalisis, obtaining a limpid and transparent colloidal suspension. By this, the method offers the advantage of producing ultrathin films without organic contaminants. This route was employed to produce films with 5, 10, 14, and 18 mol% Sb doping, with thickness ranging from 40 to 70 nm. The physical characterization of the samples showed a uniform layer deposition, resulting in good packing density and high transmittance. A preliminar electrical study confirmed the low electrical resistivity even in the ultrathin films, in such level similar of reported data. The method described is similar in some aspects to layer-by-layer (LbL) techniques, allowing fine control of thickness and interesting properties for ultrathin films, however, with low cost when compared to similar routes.

Preparation of 9/65/35 PLZT thin films deposited by a dip-coating process

Crack-free polycrystalline PLZT (Pb,a)(Zr,Ti)O-3 thin films with the perovskite structure were prepared by dir-coating using the Pechinis process. Lead acetate, hydrated lanthanum carbonate, zirconium n-propoxide and titanium isopropoxide were used as raw materials. The viscosity of the solution was adjusted in the range of 20 to 56 cP and the films were deposited by a dip-coating process on silicon (100) as substrate. Solutions with ionic concentration of 0.1 and 0.2 M were used. Thin film deposition was accomplished by dipping the substrates in the solution with control of withdrawal speed from 5 to 20 mm/min. The thin films were thermally treated in two steps: at 300 degreesC amid 650 degreesC. The influence of withdrawal speed. viscosity, heating rate and ionic concentration on the morphology of PLZT thin film was discussed. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Generalised single-equation load flow method for unbalanced distribution systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Numeric evaluation of the stiffness of log-concrete composite beams submitted the cyclical load

In this paper was evaluated, using the software ANSYS, the stiffness (El) of the log-concrete composite beams, of section T, with connectors formed by bonded-in steel rods, type CA-50, disposed in X, with application of cyclical load. The stiffness of the system was evaluated through the simulation of bending tests, considered 1/2 beam, with cyclical shipment varying among 40 % and 5 % of the strength of the connection with the load relationship R=0,125, for a total of 10 load cycles applied. The numeric results show a good agreement with experimental tests.

Multi-Agent Framework for Spatial Load Forecasting

A multi-agent framework for spatial electric load forecasting, especially suited to simulate the different dynamics involved on distribution systems, is presented. The service zone is divided into several sub-zones, each subzone is considered as an independent agent identified with a corresponding load level, and their relationships with the neighbor zones are represented as development probabilities. With this setting, different kind of agents can be developed to simulate the growth pattern of the loads in distribution systems. This paper presents two different kinds of agents to simulate different situations, presenting some promissory results.

Hydrogenated amorphous carbon as protective coating for a forming tool

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Lubricating coating prepared by PIIID on a forming tool

In this work, the performance of a-C: H films produced by the hybrid Plasma Immersion Ion Implantation and Deposition technique as lubricating layers for a steel forming tool has been investigated. Hardened steel (AISI M2, 64 HRC) plates coated with a commercial TiN layer were used as substrates and the films were deposited in a vacuum chamber fitted with two parallel-plate electrodes. The discharges were generated in atmospheres composed of 91% C2H2 and 9% Ar by the application of radiofrequency power (13.56 MHz, 100 W) to the upper electrode while the lower one, also used as the sample holder, was biased with high voltage negative pulses (3.6 kV, 30 mu s, 300 Hz). A deposition time of 840 s was used. The effects of the gas pressure, p, on thickness, molecular structure, wettability, surface morphology and topography, hardness and friction coefficient of the films lwere investigated. Film thickness increased from 0.3 to 0.5 mu m when p was increased from 2.7 to 16.5 Pa. Generally, the films were slightly hydrophilic, with contact angles of around 84 degrees, and the deposition decreased the roughness of the steel. A polymer-like structure was detected in high pressure depositions and an amorphous carbon structure derived from the low pressure procedures. Hardness decreased from 8.2 to 7.0 GPa with increasing p. Improvement in tribological performance was indicated by the fall in the friction coefficient from 0.5 to 0.2 as the deposition pressure was reduced. Operating at the latter value (of mu) would lead to a significant reduction in wear and hence to significant economy in diverse industrial applications.