Influence of the constitutive flow law in FEM simulation of the Radial forging process

Radial forging is a widely used forming process for manufacturing hollow products in transport industry. As the deformation of the workpiece, during the process, is a consequence of a large number of high-speed strokes, the Johnson-Cook constitutive law (taking into account the strain rate) seems to be well adapted for representing the material behavior even if the process is performed under cold conditions. But numerous contributions concerning radial forging analysis, in the literature, are based on a simple elastic-plastic formulation. As far as we know, this assumption has yet not been validated for the radial forging process. Because of the importance of the flow law in the effectiveness of the model, our purpose in this paper is to analyze the influence of the use of an elastic-viscoplastic formulation instead of an elastic-plastic one for modeling the cold radial forging process. In this paper we have selected two different laws for the simulations: the Johnson-Cook and the Ludwik ones, and we have compared the results in terms of forging force, product’s thickness, strains, stresses, and CPU time. For the presented study we use an AISI 4140 steel, and we denote a fairly good agreement between the results obtained using both laws

Irregular migration in senegal faith, dreams and human smuggling through the desert and sea

The paper provides a bottom up view on human smuggling facilitation and the rationale behind extremely high-risk and complex irregular migration journeys from the Kolda region of Senegal across the Sahara and through the Atlantic sea. Interviews with aspiring, returned and deported migrants as well as smugglers and their associates provide insights into the organization of migration facilitation and how this is sustained in the current policy context. The research highlights the role of religious beliefs in preparing for and interpreting the experiences of harrowing journeys with a high risk of harm and death. The study also sheds light on hitherto under-recognised gendered aspects of the infrastructure of migration facilitation in Kolda: while migration is male dominated, women play a critical role in enabling migration by mobilising religious and financial support. The paper also discusses the differences in the social constructions of male and female migration and the differences in their social relations with smugglers and other actors involved in facilitating irregular migration. In conclusion the authors suggest that there is a need to revisit migration policies that are based on dissuading migrants through risk-awareness campaigns and heightened controls towards policies that address global structural inequalities that drive migration; develop a more accurate understanding of personal and family aspirations for change; create more opportunities for legal migration; initiate discourses on culturally sensitive topics such as female migration and failed migration, and the role of Islamic spiritual leaders (Marabouts)

Extraction and Analysis of Dynamic Conversational Networks from TV Series

Identifying and characterizing the dynamics of modern tv series subplots is an open problem. One way is to study the underlying social network of interactions between the characters. Standard dynamic network extraction methods rely on temporal integration, either over the whole considered period, or as a sequence of several time-slices. However, they turn out to be inappropriate in the case of tv series, because the scenes shown onscreen alternatively focus on parallel storylines, and do not necessarily respect a traditional chronology. In this article, we introduce Narrative Smoothing, a novel network extraction method taking advantage of the plot properties to solve some of their limitations. We apply our method to a corpus of 3 popular series, and compare it to both standard approaches. Narrative smoothing leads to more relevant observations when it comes to the characterization of the protagonists and their relationships, confirming its appropriateness to model the intertwined storylines constituting the plots.Comment: arXiv admin note: substantial text overlap with arXiv:1602.0781

Chemical reduction of hexavalent chromium (VI) in soil slurry by nano zero valent iron

The increasing industrial development of recent decades has lead to the production of increasing quantities of waste containing heavy metals, elements often harmful to the environment, which in the past were not properly disposed of, thus inducing soil and groundwater pollution. In particular, chromium (Cr) and its derivatives are largely used in industries such as textiles, electronics, metallurgy, tanneries. Consequently, large quantities of this element were released into the environment due to leakage or incorrect disposal. Chromium is a transition element present in nature in three stable forms: metallic Cr, trivalent Cr(III) and hexavalent Cr(VI). Metallic Chromium is rarely found in nature, mainly as natural chrome metallic inclusions in diamonds, fragments of as meteorites and metal alloys in fluvial deposits. The trivalent form is characterized by a relatively low toxicity, while the hexavalent chromium present in different compounds of industrial origin, is considered highly toxic towards the respiratory system and carcinogenic. In the present work, lab experiments of Cr(VI) contaminated soil clean-up by chemical reduction with nanoparticles of zero valent iron (nZVI) are presented and discussed. The aim of the work was to optimize the main operative parameters of the reduction process (pH, nZVI concentration, liquid/solid ratio). Cr(VI) reduction using nZVI was found to obey a pseudo-first-order kinetic: the kinetic constant depended upon the nZVI: Cr(VI) ratio. The use of nZVI in combination with sodium dithionite was also studied, by performing tests in batch conditions at pH = 1.3, in order to assess the optimal ratio between nZVI and Cr(VI), and between dithionite and Cr(VI). The results obtained showed an increase of Cr(VI) reduction rate with respect to the tests carried only with nZVI: for long treatment times, up to 24 hours, an almost total removal of Cr(VI) was achieved when a large excess of reagents was used