Study of Arc Mobility and Reignition in a Static Gap Discharge with Magnetic Field
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New contact material for reduction of arc duration for dc application
The phenomenon of arcing is the major cause of electrical contact degradation in electrical switches. Degradation involves contact erosion and/or welding. The use of special contact material and that of specific material processing may permit contact erosion to be reduced, in particular by shortening the arc duration. A short review of these approaches is presented in the first part of this paper. In the second part, the development of a new self-blowing contact material is described. This material has been tested under dc voltages from 14 V to 42 V. A reduction of the arc duration by a factor of 4 approximately was obtained as was a concomitant reduction of the extinction gap to less than 2 mm. This material will contribute to achieving better reliability in high current-high voltages breaking devices, and will aid in their miniaturization, e.g. in relays.
As práticas profissionais no campo público de atenção à saúde bucal: o caso de dois municípios da Bahia
This paper examines the working facilities and processes of dentists in the primary healthcare systems of two towns in Bahia State, Brazil, striving to analyze the extent to which factors related to dental care, training, placement and professional profiles influence their practices. Semi-structured interviews were conducted with nine dentists in both towns, with work process organization patterns in Municipality C being closer to the structuring principles of Brazil's National Health System than in Municipality E. This seems to be related to management characteristics, with networking links among individual, collective, and preventive clinical activities and planning noted in Municipality C. Despite these differences, the practitioners presented similarities in terms of dual militancy and perceptions of the public and private healthcare fields. The hegemony of the private sector seems to be influencing the professional practices of dentists in the public health system.