Bostonia Magazine. Volume 56

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

A Review of the Erosion of Thermal Barrier Coatings.

The application of thermal barrier coatings (TBCs) to components with internal cooling in the hot gas stream of gas turbine engines has facilitated a steep increase in the turbine entry temperature and the associated increase in performance and efficiency of gas turbine engines. However, TBCs are susceptible to various life limiting issues associated with their operating environment including erosion, corrosion, oxidation, sintering and foreign object damage (FOD). This is a review paper that examines various degradation and erosion mechanisms of TBCs, especially those produced by electron beam physical vapour deposition (EB-PVD). The results from a number of laboratory tests under various impact conditions are discussed before the different erosion and FOD mechanisms are reviewed. The transitions between the various erosion mechanisms are discussed in terms of the D/d ratio (contact area diameter/column diameter), a relatively new concept that relates the impact size to the erosion mechanism. The effects of ageing, dopant additions and calciumâ  magnesiumâ  aluminaâ  silicates on the life of TBCs are examined. It is shown that while ageing increases the erosion rate of EB-PVD TBCs, ageing of plasma sprayed TBCs in fact lowers the erosion rate. Finally modelling of EB-PVD TBCs is briefly intr

Development and Transfer of Innovative Problem Solving Strategies and Related Confidence in Biomedical Engineering

Twenty-nine biomedical engineering (BME) undergraduates participated in a challenge-based instruction biotransport course, offered by the UT Austin BME Department in an accelerated format, at the University of Cambridge. Students’ attitudes toward, and aptitude for solving genuine and complex biomedical problems were assessed throughout the semester through surveys, interviews, observations, and in-class examinations. Students’ aptitude for problem solving improved throughout the semester, in a manner independent of content knowledge development. By the end of the semester, students readily transferred the problem-solving framework, learned within a biotransport context, to solve biomechanics problems. Additionally, we observed significant increases over time in students’ confidence in their ability to complete challenges within and outside of the biotransport domain. We believe that this illustrative case study provides significant quantitative evidence supporting the effectiveness of challenge-based pedagogies for engineering courses.Cockrell School of Engineerin

Rethinking Space, Light, And Pedagogy

Classic

Unit circle MVDR beamformer

The array polynomial is the z-transform of the array weights for a narrowband planewave beamformer using a uniform linear array (ULA). Evaluating the array polynomial on the unit circle in the complex plane yields the beampattern. The locations of the polynomial zeros on the unit circle indicate the nulls of the beampattern. For planewave signals measured with a ULA, the locations of the ensemble MVDR polynomial zeros are constrained on the unit circle. However, sample matrix inversion (SMI) MVDR polynomial zeros generally do not fall on the unit circle. The proposed unit circle MVDR (UC MVDR) projects the zeros of the SMI MVDR polynomial radially on the unit circle. This satisfies the constraint on the zeros of ensemble MVDR polynomial. Numerical simulations show that the UC MVDR beamformer suppresses interferers better than the SMI MVDR and the diagonal loaded MVDR beamformer and also improves the white noise gain (WNG).Comment: Accepted to ICASSP 201