In‐situ microscopic analysis of ferritic ductile iron during tensile loading: Relation between matrix heterogeneities and damage mechanisms

An in‐situ microscopic analysis of the damage mechanisms of ferritic ductile iron under uniaxial tensile testing is carried out in this work. The experimental methodology combines specialized metallography techniques, in‐situ optical microscopy observation during loading, and digital image correlation analysis to obtain the strain values at the microscopic level. The results show that the crack initiation is preferentially located at matrix‐nodule interface and ferritic grain boundaries. The propagation of multiple cracks across the internodular ligaments that later coalesce into a single dominant crack is responsible for the final fracture. Noticeably, despite the heterogeneous nature of the Last‐to‐Freeze zones, the cracks propagate avoiding these microsegregated areas. The results provide new insights for the better understanding of the influence of ferritic ductile iron heterogeneities on the fracture process for quasistatic uniaxial loading.     

Theoretical analysis of conjugated heat transfer with a single domain formulation and integral transforms

The present work advances an analytical approach for conjugated conduction-convection heat transfer problems, by proposing a single domain formulation for modeling both the fluid stream and the channel wall regions. Making use of coefficients represented as space variable functions with abrupt transitions occurring at the fluid-wall interface, the mathematical model is fed with the information concerning the transition of the two domains, unifying the model into a single domain formulation with space variable coefficients. The Generalized Integral Transform Technique (GITT) is then employed in the hybrid numerical-analytical solution of the resulting convection-diffusion problem with variable coefficients, and critically compared for two alternative solution paths. A test problem is chosen that offers an exact solution for validation purposes, based on the extended Graetz problem including transversal conduction across the channel walls. The excellent agreement between approximate and exact solutions demonstrates the feasibility of the approach in handling more involved conjugated problems.     

Low-density polyethylene/polyamide 6 blends from multilayer films waste

Multilayer films combine properties of different polymers in a single material, attending specifications to applications such as packaging. However, the mechanical recycling for this material king is commercially less interesting because the polymeric components cannot easily be separated and the direct mechanical processing of the material leads to the immiscible and incompatible polymeric blends. The aim of this study was to evaluate properties of the blends of low-density polyethylene (LDPE) and polyamide 6 (PA6) generated from mechanical recycling of multilayer films constituted by LDPE and PA6, containing maleic anhydride grafted polyethylene (PE-g-MA) as compatibilizing agent and different amounts of virgin PA6. The LDPE/PA6 blends are immiscible for all composition and the use of PE-g-MA has showed little effect on the compatibility of the blends with high content of PA6. However, LDPE/PA6 blends with PA6 content up to 20 wt % showed considerable performance for mechanical performance that can justify the mechanical recycling of the material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47456     

Modeling Power Transformer Field Drying Processes

Power transformer field drying is becoming a habitual practice because water is damaging for transformer insulation, and its presence increases the probability of unexpected failures. Different drying methods are currently being used by electrical companies but sometimes without a profound knowledge of the drying processes involved, and consequently drying is not as effective as would be desirable.

Physical models have been developed by the authors in order to study power transformer drying processes. The use of the models will help to plan more effective drying processes, tailoring the drying times and drying conditions for each particular case. The models have been tested in a test transformer fitted with sensors. In order to monitor the process, insulation samples were extracted from the transformer before and after the process.

In this article, several transformer drying procedures are described. Theoretical models and their experimental validation processes are reported. Finally, some general recommendations about transformer drying in the field are provided.     

A reconstruction method for electrical capacitance tomography based on image fusion techniques

In this work, a method based on image fusion for the formation of Electrical Capacitance Tomography (ECT) images is presented. This method is based on the modification of the classical algebraic superposition of sensitivity maps, weighted with the inter-electrode capacitance measurements, which is the basis of most of the existing image reconstruction algorithms. This fusion-based approach replaces this superposition with the scalar multiplication of partial images generated considering only the data corresponding to fixed source electrodes. Results obtained with this new method show that the quality of the images can be improved without any image post-processing, which is very interesting especially for real-time applications.     

Perceptually Optimized Coded Apertures for Defocus Deblurring

The field of computational photography, and in particular the design and implementation of coded apertures, has yielded impressive results in the last years. In this paper we introduce perceptually optimized coded apertures for defocused deblurring. We obtain near‐optimal apertures by means of optimization, with a novel evaluation function that includes two existing image quality perceptual metrics. These metrics favour results where errors in the final deblurred images will not be perceived by a human observer. Our work improves the results obtained with a similar approach that only takes into account the L2 metric in the evaluation function.     

ISM-AC: an immune security model based on alert correlation and software-defined networking

International Journal of Information Security - Anomaly-based detection techniques have a high number of false positives, which degrades the detection performance. To address this issue, we propose...