Modeling programming knowledge for mentoring at scale

In large programming classes, MOOCs or online communities, it is challenging to find peers and mentors to help with learning specific programming concepts. In this paper we present first steps towards an automated, scalable system for matching learners with Python programmers who have expertise in different areas. The learner matching system builds a knowledge model for each programmer by analyzing their authored code and extracting features that capture domain knowledge and style. We demonstrate the feasibility of a simple model that counts the references to modules from the standard library and Python Package Index in a programmers' code. We also show that programmers exhibit self-selection using which we can extract the modules a programmer is best at, even though we may not have all of their code. In our future work we aim to extend the model to encapsulate more features, and apply it for skill matching in a programming class as well as personalizing answers on StackOverflow.Massachusetts Institute of Technology. Undergraduate Research Opportunities Progra

Hypolimnion reaeration of small reservoirs and lakes

Students supported: 1 Student AssistantThe purposes of this research were to study the oxygen transfer rates and the oxygen transfer efficiencies of different types of aerators using different sources of oxygen in different types of water bodies, and to evaluate the number of diffusers required to be installed in a selected lake for hypolimnion aeration. The experiments were conducted using a specially designed column. Four types of aerators, including a cylindrical stone diffuser, a spherical stone diffuser, and 2 ceramic diffusers (types A and B) which differed in pore size, were utilized as the aerators. The water bodies selected for the studies were Rolla tap water, Bray's Lake water, and Frisco Pond water. Air and pure oxygen were the two sources of oxygen studied. The oxygen transfer rates and efficiencies of the ceramic diffusers were found to be greater than those of the stone diffusers. Ceramic diffuser type B was the best aerator tested. For a given type of diffuser, a higher transfer rate was generated when pure oxygen was used instead of air. Hypolimnion aeration of Bray's Lake using the diffusers studied in this research was feasible. The number of diffuser units required for hypolimnion aeration may be minimized if ceramic diffuser type B were employed when air was used, or if ceramic diffuser type A were operated when pure oxygen was utilized for aeration.Project # A-053-MO Agreement # 14-31-0001-353

The Casimir force on a surface with shallow nanoscale corrugations: Geometry and finite conductivity effects

We measure the Casimir force between a gold sphere and a silicon plate with nanoscale, rectangular corrugations with depth comparable to the separation between the surfaces. In the proximity force approximation (PFA), both the top and bottom surfaces of the corrugations contribute to the force, leading to a distance dependence that is distinct from a flat surface. The measured Casimir force is found to deviate from the PFA by up to 15%, in good agreement with calculations based on scattering theory that includes both geometry effects and the optical properties of the material