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Many accidents always happen in the electricity distribution sector, which requires the use of control strategies in this field. Therefore, this study presented a risk assessment method based on a fuzzy Bayesian network (FBN) and William Fine method in low-voltage power distribution systems to reduce the structural uncertainties of the studies and examined the reliability of these systems to achieve proper performance in emergencies. The first step is to develop a fault tree (FT) and event tree (ET) in bow tie (BT) format. In this study, fuzzy theory and expert judgment were used to qualitatively analyze the root events affecting the system failure and determine the relevant probabilities. Then, deductive and inductive reasoning was done after determining the likelihood of basic events (BEs) and establishing the Bayesian network (BN). Then, the final risk was estimated using William Fine's method and fuzzy logic. The results of a case study in a low-voltage power distribution system showed that there were 36 BEs and 20 intermediate events (IEs) for system failure, and the reliability of the system was obtained as 0.96654476 and 0.96654476 based on the FT and FBN, respectively. According to the results of BE25 (no installation of the earth) and BE18 (contact of metal objects with the live wire), the most critical events were based on FBN. The results showed that FBN simulation and its combination with static methods such as BT and William Fine provide a suitable method for the accurate identification of distribution systems. Therefore, the approach of the present study can help the decision makers and analysts of the electricity industry to prevent possible failures due to system changes. [ABSTRACT FROM AUTHOR]

The Z‐source inverter was introduced to overcome shortcomings of voltage source inverter and current source inverter. In this paper, the concept of one switched‐inductor Z‐source inverter is extended to switched‐capacitor inductor ZSI with an impedance network. In the proposed inverter, capacitors are used instead of the side diodes of the one switched inductor Z‐source inverter. The proposed inverter has a higher boost factor compared to One SL‐ZSI and quasi‐ZSI. Also, it has lower voltage stress compared to similar inverters. The proposed inverter can be extended to n cases in cascade form. The components used in the proposed topology are lower than the SL‐ZSI. The analysis, derivation of boost factor, capacitor voltages, diode voltages, and switch voltages stress of the proposed inverter topology are carried out and are compared with the similar inverters. The advantages of the proposed structure are verified through simulation and implementation. The simulation is performed in MATLAB/SIMULINK. [ABSTRACT FROM AUTHOR]

ABSTRACT The main aim of this study was to investigate the usability of polyurethane (PU) and polyacrylonitrile (PAN) nanofibers for improving the sound absorption of conventional polyester nonwovens in wide band of frequencies along with weight and thickness reduction. The effect of nanofiber and nonwoven layers number, nanofiber layers surface density, and the type of nanofiber polymer on the sound absorption was studied. To find the optimum conditions for achieving high sound absorption, response surface methodology was used. The results showed that the sound absorption of composite samples is improved when the nanofiber layer number or its surface density increased. The results also showed that the sound absorption of composites is enhanced by using PAN instead of PU. At a constant surface density, the higher resonant peak, without shifting, was achieved with increasing the nanofiber layers number. Optimization process showed that samples containing PAN nanofiber layers with surface density of 4.72 g/m2 and six nonwoven layers have highest average sound absorption coefficient. [ABSTRACT FROM AUTHOR]

In this study, flexible polyurethane (PU) nanocomposite foams were prepared by in situ polymerization. The effects of incorporation of nanoparticles on the morphological and structural developments and the relation between this development and mechanical properties of the PU foam were demonstrated. The effects of three different contents (low, moderate, and high) of nanoclay and multiwall carbon nanotubes (MWNTs) loading on foam morphology, structure, kinetics of foaming reactions, and mechanical properties were separately investigated. By adding MWNTs and nanoclay in foams, the foam morphology improved, in which cell density increased and smaller cells were obtained. The mechanical properties of foam especially tensile strength have been increased in the presence of nanoparticles. With enhancing the nanoclay content, the tensile strength of nanocomposite foam has improved but in the case of MWNTs contrary effects were observed. An increase in nanoparticle amount leads to a lower cell density. In general, the incorporation of both nanoparticles (nanoclay and MWNTs) in the foam structure leads to a lower foaming reaction rate that affects mechanical properties of foams. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E545-E555, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21300 [ABSTRACT FROM AUTHOR]