Worcester Polytechnic Institute

About: Worcester Polytechnic Institute is a education organization based out in Worcester, Massachusetts, United States. It is known for research contribution in the topics: Computer science & Population. The organization has 6270 authors who have published 12704 publications receiving 332081 citations. The organization is also known as: WPI.

The sum is greater than the parts: ensembling models of student knowledge in educational software

Abstract: Many competing models have been proposed in the past decade for predicting student knowledge within educational software. Recent research attempted to combine these models in an effort to improve performance but have yielded inconsistent results. While work in the 2010 KDD Cup data set showed the benefits of ensemble methods, work in the Genetics Tutor failed to show similar benefits. We hypothesize that the key factor has been data set size. We explore the potential for improving student performance prediction with ensemble methods in a data set drawn from a different tutoring system, the ASSISTments Platform, which contains 15 times the number of responses of the Genetics Tutor data set. We evaluated the predictive performance of eight student models and eight methods of ensembling predictions. Within this data set, ensemble approaches were more effective than any single method with the best ensemble approach producing predictions of student performance 10% better than the best individual student knowledge model.

Nuclear magnetic resonance properties of rocks at elevated temperatures

Abstract: Although the NMR properties of fluid-saturated rocks have been studied for decades, the temperature dependence of these properties has never been systematically investigated. A hot-air-flow loop has been constructed that can elevate the temperature of a core sample. An algorithm to estimate the distribution of NMR relaxation times from Fast Inversion Recovery/CPMG data has been developed and used to analyze the effects of temperature. Proton magnetic resonance measurements have been made on an assortment of water-saturated sandstones and carbonates and an oil-saturated sandstone at temperatures ranging from 25 to 175°C. The relaxation times of all the water-saturated sandstones and most of the carbonates depend only weakly on temperature. This indicates that the water-saturated rocks studied are in the fast-diffusion limit and the intrinsic surface relaxation strength is independent of temperature. In all the rocks studied the magnitude of the NMR signal, which is proportional to porosity, decreases with increasing temperature in accordance with the Curie Law. Data from oil-saturated sandstone clarify the roles of molecular diffusion, material-specific surface interactions, and bulk fluid relaxation.