Hydrochemical evaluation of the quality of some Brazilian waters

This investigation was carried out within the Parane sedimentary basin and neighbourhood in Brazil and involved the sampling of different water types with the purpose of evaluating its quality. Several methods were utilized for acquiring the hydrochemical data and a novel technique has been developed for evaluating the gross alpha and beta radioactivities in water, through a combined gamma-alpha spectrometry technique. The results obtained for the analyzed samples were compared with the guideline values established by the São Paulo State and Brazilian Health Ministry legislations for defining potable water standards and for the prevention and control of pollution in the environment. The hydrochemical data allowed evaluation of diverse problems related to the interaction between society and the environment such as sugarcane production and the releases associated with gas stations suppliers. The geogenic input of sulfate in groundwater was also identified. The established radiometric technique was properly calibrated and successfully applied to the analysis of different water types utilized for human consumption.

Variable speed refrigeration system with HPF input rectifier stage

This paper is based on the analysis and implementation of a new drive system applied to refrigeration systems, complying with the restrictions imposed by the IEC standards (Harmonic/Flicker/EMI-Electromagnetic Interference restrictions), in order to obtain high efficiency, high power factor, reduced harmonic distortion in the input current and reduced electromagnetic interference, with excellent performance in temperature control of a refrigeration prototype system (automatic control, precision and high dynamic response). The proposal is replace the single-phase motor by a three-phase motor, in the conventional refrigeration system. In this way, a proper control technique can be applied, using a closed-loop (feedback control), that will allow an accurate adjustment of the desirable temperature. The proposed refrigeration prototype uses a 0.5Hp three-phase motor and an open (Belt-Drive) Bitzer IY type compressor. The input rectifier stage's features include the reduction in the input current ripple, the reduction in the output voltage ripple, the use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the IEC61000-3-2 standards. The digital controller for the output three-phase inverter stage has been developed using a conventional voltage-frequency control (scalar V/f control), and a simplified stator oriented Vector control, in order to verify the feasibility and performance of the proposed digital controls for continuous temperature control applied at the refrigerator prototype. ©2008 IEEE.