Review and analysis of the DNW/Model 360 rotor acoustic data base

A comprehensive model rotor aeroacoustic data base was collected in a large anechoic wind tunnel in 1986. Twenty-six microphones were positioned around the azimuth to collect acoustic data for approximately 150 different test conditions. A dynamically scaled, blade-pressure-instrumented model of the forward rotor of the BH360 helicopter simultaneously provided blade pressures for correlation with the acoustic data. High-speed impulsive noise, blade-vortex interaction noise, low-frequency noise, and broadband noise were all captured in this extensive data base. Trends are presentes for each noise source, with important parametric variations. The purpose of this paper is to introduce this data base and illustrate its potential for predictive code validation

Sustainability science graduate students as boundary spanners

Graduate training in sustainability science (SS) focuses on interdisciplinary research, stakeholder-researcher partnerships, and creating solutions from knowledge. But becoming a sustainability scientist also requires specialized training that addresses the complex boundaries implicit in sustainability science approaches to solving social-ecological system challenges. Using boundary spanning as a framework, we use a case study of the Sustainability Solutions Initiative (SSI) at the University of Maine to explicate key elements for graduate education training in SS. We used a mixed-methods approach, including a quantitative survey and autoethnographic reflection, to analyze our experiences as SSI doctoral students. Through this research, we identified four essential SS boundaries that build on core sustainability competencies which need to be addressed in SS graduate programs, including: disciplines within academia, students and their advisors, researchers and stakeholders, and place-based and generalizable research. We identified key elements of training necessary to help students understand and navigate these boundaries using core competencies. We then offer six best practice recommendations to provide a basis for a SS education framework. Our reflections are intended for academic leaders in SS who are training new scientists to solve complex sustainability challenges. Our experiences as a cohort of doctoral students with diverse academic and professional backgrounds provide a unique opportunity to reflect not only on the challenges of SS but also on the specific needs of students and programs striving to provide solutions

Wetting layer thickness and early evolution of epitaxially strained thin films

We propose a physical model which explains the existence of finite thickness wetting layers in epitaxially strained films. The finite wetting layer is shown to be stable due to the variation of the non-linear elastic free energy with film thickness. We show that anisotropic surface tension gives rise to a metastable enlarged wetting layer. The perturbation amplitude needed to destabilize this wetting layer decreases with increasing lattice mismatch. We observe the development of faceted islands in unstable films.Comment: 4 pages, 3 eps figure