Evaluation of thermal ageing conditions in 17-4 PH stainless steel by Fourier descriptor analysis of magnetic hysteresis loops

Fourier descriptor analysis of magnetic hysteresis loops has been used to assess the conditions of isothermal and isochronal ageing in quench-aged precipitation hardening 17-4 PH stainless steel. The Fourier descriptors (i.e. sine harmonic coefficients in the Fourier series expansion of the magnetic flux density as a function of current arc length value of the ascending branch of hysteresis loop) have been found to be suitable for assessment of aged conditions of this material. This technique serves as a reliable tool to distinguish (i) as-quenched specimenen from the quench-aged specimens and (ii) specimens with different ageing conditions. The results obtained indicate that the Fourier descriptor technique is a promising tool for assessment of ageing conditions in 17-4 PH steel

Text mining in education

The explosive growth of online education environments is generating a massive volume of data, specially in text format from forums, chats, social networks, assessments, essays, among others. It produces exciting challenges on how to mine text data in order to find useful knowledge for educational stakeholders. Despite the increasing number of educational applications of text mining published recently, we have not found any paper surveying them. In this line, this work presents a systematic overview of the current status of the Educational Text Mining field. Our final goal is to answer three main research questions: Which are the text mining techniques most used in educational environments? Which are the most used educational resources? And which are the main applications or educational goals? Finally, we outline the conclusions and the more interesting future trends