Abstract. Electrical conductivity of 150-200 μm thick polysulfone films loaded with 0.05-0.75% w/w multiwall carbon nanotubes was systematically investigated for two types of dispersion states, uniformly dispersed and agglomerated at the micro-scale. The percolation threshold was found at 0.11% and 0.068% w/w for the uniformly dispersed and agglomerated films, respectively. Overall, the conductivity of the films with agglomerated nanotubes was higher than that of the uniformly dispersed ones, with marked differences of 2 to 4 orders of magnitude for carbon nanotubes loadings in the upper vicinity of the percolation threshold (0.1-0.3% w/w). The increased conductivity of the agglomerated state is explained by the increased nanotube-to-nanotube contact after the percolating network has formed, which facilitates electron transfer.

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The emergence of modern technologies, such as Wireless Sensor Networks (WSNs), the Internet-of-Things (IoT), and Machine-to-Machine (M2M) communications, involves the use of batteries, which pose a serious environmental risk, with billions of batteries disposed of every year. However, the combination of sensors and wireless communication devices is extremely power-hungry. Energy Harvesting (EH) is fundamental in enabling the use of low-power electronic devices that derive their energy from external sources, such as Microbial Fuel Cells (MFC), solar power, thermal and kinetic energy, among others. Plant Microbial Fuel Cell (PMFC) is a prominent clean energy source and a step towards the development of self-powered systems in indoor and outdoor environments. One of the main challenges with PMFCs is the dynamic power supply, dynamic charging rates and low-energy supply. In this paper, a PMFC-based energy harvester system is proposed for the implementation of autonomous self-powered sensor nodes with IoT and cloud-based service communication protocols. The PMFC design is specifically adapted with the proposed EH circuit for the implementation of IoT-WSN based applications. The PMFC-EH system has a maximum power point at 0.71 V, a current density of 5 mA cm − 2 , and a power density of 3.5 mW cm − 2 with a single plant. Considering a sensor node with a current consumption of 0.35 mA, the PMFC-EH green energy system allows a power autonomy for real-time data processing of IoT-based low-power WSN systems.

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Electric arc furnaces (EAFs) contribute to almost one third of the global steel production. Arc furnaces use a large amount of electrical energy to process scrap or reduced iron and are relevant to study because small improvements in their efficiency account for significant energy savings. Optimal controllers need to be designed and proposed to enhance both process performance and energy consumption. Due to the random and chaotic nature of the electric arcs, neural networks and other soft computing techniques have been used for modeling EAFs. This study proposes a methodology for modeling EAFs that considers the time varying arc length as a relevant input parameter to the arc furnace model. Based on actual voltages and current measurements taken from an arc furnace, it was possible to estimate an arc length suitable for modeling the arc furnace using neural networks. The obtained results show that the model reproduces not only the stable arc conditions but also the unstable arc conditions, which are difficult to identify in a real heat process. The presented model can be applied for the development and testing of control systems to improve furnace energy efficiency and productivity.

El consumo de tabaco en las adolescentes se está incrementando aceleradamente, con los consecuentes efectos adversos para su propia salud y la de sus descendientes. Con el propósito de someter a prueba, mediante técnicas de modelamiento estructural, un modelo explicativo de la intención de fumar en las adolescentes, se aplicó un instrumento validado a 386 mujeres estudiantes de escuelas secundarias públicas y privadas. El modelo planteó el efecto de seis factores protectores y de riesgo sobre la intención de fumar, así como la relación entre éstos. Tales variables fueron obtenidas a partir de un análisis de regresión múltiple en el que se incluyeron originalmente 25. Los resultados indicaron que los amigos fumadores constituyen la principal influencia en la intención de fumar de las chicas adolescentes. Los padres juegan un papel protector fundamental, ya que, al supervisar sus actividades y al no permitir el consumo de tabaco en casa, disminuyen la intención de fumar de sus hijas, controlan la presencia de amigos fumadores y moderan su rebeldía, la cual influye en sus creencias respecto de los beneficios de fumar. Creer que el tabaco es realmente adictivo constituye también un factor protector para las adolescentes. Se discuten propuestas para aplicar los hallazgos en programas para la prevención del tabaquismo femenino, en los que se incluya a los padres. ABSTRACTTobacco use among girls is increasing at an accelerating pace, with adverse effects for their own health and that of their potential offspring. In order to test, through structural equation modeling techniques, an explanatory model of smoking intention in young girls, we applied a validated instrument to 386 female students at state and private secondary schools. The model considered the effect of six protective and risk factors on smoking intention, as well as the relationship between them. These variables were obtained from a multiple regression analysis which included a total of 25. The results indicated that having friends who smoke cigarettes constitutes the main influence on smoking intention in young girls. Parents play a fundamental protective role, since, on supervising their daughters' activities and prohibiting smoking at home, the girls' smoking intention is decreased, presence of friends who smoke is controlled, and rebellious behavior is moderated, and this influences the girls' beliefs about the benefits of smoking. Believing that tobacco is really addictive is also a protective cognitive factor for such girls. Proposals are discussed for applying the findings to prevention programs addressing smoking in young girls, and in which parents are included.

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