RESUMO
An experimental method exploiting the capacitive response of most materials is here revised. The procedure called the "Voltage Ramp Method" (VRM) is based on applying proper voltage ramp cycles over time and measuring electrical current intensity flowing through the material sample. In the case of an ideal capacitor, a current plateau should be easily measured, and the capacitance value precisely determined. However, most media, e.g., semiconductors and insulating polymers, show dielectric absorption and hence electric leakage effects. Therefore, the VRM method allows simultaneous determination of their equivalent capacitance and resistance. Some case studies are discussed as concerning the application of VRM to both standard and actual media. A figure of merit of the method is the percentage difference between 2.5% and 1.5% with respect to the nominal values of a commercial capacitor and resistor, respectively. The simulation modeling of the material electrical response is compared to the experimental data also on polymer nanocomposites suitable for energy harvesting.
RESUMO
This article describes in detail each stage of the shoe manufacturing process: design, cutting and shearing, sewing and trimming, assemblage, sole preparation, finishing, packaging and stocking, shoe manufacturing with synthetic materials. It will then discuss new technologies and their impact on the improvement of the worker's health, safety and convenience. A definition of the shoe parts and of the materials and machinery employed in its production will be provided, as well as a synthesis of the occupational hazards involved in each department. Although dealing with competitors who can take advantage of low-cost production and lack of concern for labour protection and environmental issues, the industry should always take great care of topics such as innovation and automation, but also workplace health and safety, while pushing the limits of that technological advance which companies have to face.
