Light-induced electric dipole relaxation in synthetic and natural alexandrite

We present results of thermally stimulated depolarization current (TSDC) measurements in synthetic and natural alexandrite, which show TSDC bands related to the presence of electric dipoles in both types of samples. Synthetic material shows a wide TSDC band with a peak at 179 K, which can be fitted by two distinct relaxing dipole distributions. For natural alexandrite the TSDC band has a maximum around 195 K and can be fitted by three different distributions. Both samples present one of the calculated curves with a peak about 179 K, with activation energy of 0.57 eV and constant relaxation time of 1 × 10-14 sec. Photo-induced TSDC shows that TSDC bands can also be generated by simultaneous application of light and an electric field at 77 K.

PMUs optimized allocation using a tabu search algorithm for fault location in electric power distribution system

Phasor Measurement Units (PMUs) optimized allocation allows control, monitoring and accurate operation of electric power distribution systems, improving reliability and service quality. Good quality and considerable results are obtained for transmission systems using fault location techniques based on voltage measurements. Based on these techniques and performing PMUs optimized allocation it is possible to develop an electric power distribution system fault locator, which provides accurate results. The PMUs allocation problem presents combinatorial features related to devices number that can be allocated, and also probably places for allocation. Tabu search algorithm is the proposed technique to carry out PMUs allocation. This technique applied in a 141 buses real-life distribution urban feeder improved significantly the fault location results. © 2004 IEEE.

Experimental study of the centripetal force

We describe an experimental set-up for studying and determining the centripetal force acting on a body whose mass and radius of circular trajectory are known. The experimental behaviour is determined and compared with theoretical predictions by using a system that allows for the evaluation of the angular velocity by means of electric current measurements, and by assuming a potential dependence of the force on the body mass, radius and angular velocity. © 2007 IOP Publishing Ltd.

Electromyographic evaluation of the upper lip according to the breathing mode: A longitudinal study

The present study aimed at analyzing and comparing longitudinally the EMG (electromyographic activity) of the superior orbicularis oris muscle according to the breathing mode. The sample, 38 adolescents with Angle Class II Division 1 malocclusion with predominantly nose (PNB) or mouth (PMB) breathing, was evaluated at two different periods, with a two-year interval between them. For that purpose, a 16-channel electromyography machine was employed, which was properly calibrated in a PC equipped with an analogue-digital converter, with utilization of surface, passive and bipolar electrodes. The RMS data (root mean square) were collected at rest and in 12 movements and normalized according to time and amplitude, by the peak value of EMG, in order to allow comparisons between subjects and between periods. Comparison of the muscle function of PNB and PMB subjects at period 1 (P1), period 2 (P2) and the variation between periods (Δ) did not reveal statistically significant differences between groups (p < 0.05). However, longitudinal evaluation of the muscle function in PNB and PMB subjects demonstrated different evolutions in the percentage of required EMG for accomplishment of the movements investigated. It was possible to conclude that there are differences in the percentage of electric activity of the upper lip with the growth of the subjects according to the breathing mode.

The sustainability of development in Latin America and the Caribbean: challenges and opportunities

Includes bibliography

A preliminary assessment of the policies implemented by the governments of Latin America and the Caribbean in response to the crisis - May 2010 Meeting

Includes bibliography

Macroeconomic policies in times of crisis: options and perspectives

Includes bibliography

Two decades of adjustment and agricultural development in Latin America and the Caribbean

Includes bibliography

Theory and practice of industrial policy: evidence from the Latin American experience

Includes bibliography

To estimate the electric field near electric energy transmission systems by use simple software

The main objective this article is describe a methodology for the calculation of the profile of the electric field in the level soil and proximities originated by electric energy transmission systems real and in operation in the country. It also is commented the equation used and your computational implementation in order to agile and to optimize the studies. The results of simulations were just presented for the transmission system in the voltage class 500 kV for simplify the understanding and space restriction in the article, very although five others types of configurations have also been used in the complete study with very voltages and respective classes. The results were animating and very nearby of values well-known of electric field of other and publications traditional in the area. The graphic exits of program for better visual comprehension and understanding went in accomplished in the plan and in the space © 2010 IEEE.

Manual for completing the questionnaire on measures affecting services trade in the hemisphere

Includes bibliography

Proposals for improvement of methodology and process of collecting and analyzing compatibility of power quality indicators in distribution systems

This article aims to present proposals for improvement of key standards and resolutions concerned about the methodology for calculating the indicator of total harmonic voltage distortion, and should contribute to the process of examining the compatibility of potentially disturbing loads in electric power quality in distribution systems. These proposals were drawn from the analysis of results from measurement campaigns conducted in a case study including analysis of the connection of a new induction furnace in a foundry served by a distributor of São Paulo state. A general historical situating the quality of electric energy in the electricity sector is presented, and methodological guidelines and procedures used in experimental trials are shown. The analysis and discussion of results are prepared to answer the main questions that arise during the implementation of standards, resolutions and procedures. © 2011 IEEE.

Estimativa do tempo de produção de chorume em aterro controlado por meio de medidas de resistividade elétrica

Landfill is an engineering work that aims at to accommodate residues in the smallest possible space in the soil, with minimum damages to the environment and the public health. One in the constructive forms of a controlled landfill is the excavation of ditches with appropriate dimensions, for disposition of solid residues without compactation or impermeabilization. Liquid effluents generated for similar volumes of residues, disposed in ditches with ages different from closing, it should result in physical and chemical alterations you correlated at the time of residence materials. With base in this hypothesis, measures of electric resistivity were accomplished through the of Eletrical Resistivity geophysical method, on residues ditches closed annually between 12/2001 and 12/2007, localized in control landfill of the Cordeirópolis city (SP). The leachate is a liquid effluent generated by the decomposition of organic matter and characterized by high content in total dissolved solids, whose interaction with geological environment results in alterations in terms of electrical resistivity susceptible to detection for the geophysical instrumental. The results suggest a resistivity reduction for leachate percolation produced for ditches recently and increase progressive of the resistivity for older ditches. The statistical comparative analysis with reference values for the area suggests ages of the finish production and percolation leachate for soil and rock below the ditches.

Harmonic propagation analysis in electric energy distribution systems

An important alteration of the equivalent loads profile has been observed in the electrical energy distribution systems, for the last years. Such fact is due to the significant increment of the electronic processors of electric energy that, in general, behave as nonlinear loads, generating harmonic distortions in the currents and voltages along the electric network. The effects of these nonlinear loads, even if they are concentrated in specific sections of the network, are present along the branch circuits, affecting the behavior of the entire electric network. For the evaluation of this phenomenon it is necessary the analysis of the harmonic currents flow and the understanding of the causes and effects of the consequent voltage harmonic distortions. The usual tools for calculation the harmonic flow consider one-line equivalent networks, balanced and symmetrical systems. Therefore, they are not tools appropriate for analysis of the operation and the influence/interaction of mitigation elements. In this context, this work proposes the development of a computational tool for the analysis of the three-phase harmonic propagation using Norton modified models and considering the real nature of unbalanced electric systems operation. © 2011 IEEE.

Two decades of adjustment and agricultural development in Latin America and the Caribbean

Includes bibliography