A cross-institutional analysis of the effects of broadening trainee professional development on research productivity

PhD-trained scientists are essential contributors to the workforce in diverse employment sectors that include academia, industry, government, and nonprofit organizations. Hence, best practices for training the future biomedical workforce are of national concern. Complementing coursework and laboratory research training, many institutions now offer professional training that enables career exploration and develops a broad set of skills critical to various career paths. The National Institutes of Health (NIH) funded academic institutions to design innovative programming to enable this professional development through a mechanism known as Broadening Experiences in Scientific Training (BEST). Programming at the NIH BEST awardee institutions included career panels, skill-building workshops, job search workshops, site visits, and internships. Because doctoral training is lengthy and requires focused attention on dissertation research, an initial concern was that students participating in additional complementary training activities might exhibit an increased time to degree or diminished research productivity. Metrics were analyzed from 10 NIH BEST awardee institutions to address this concern, using time to degree and publication records as measures of efficiency and productivity. Comparing doctoral students who participated to those who did not, results revealed that across these diverse academic institutions, there were no differences in time to degree or manuscript output. Our findings support the policy that doctoral students should participate in career and professional development opportunities that are intended to prepare them for a variety of diverse and important careers in the workforce

Penetration of a glass-faced transparent elastomeric resin by a lead-antimony- cored bullet

The penetration of the lead antimony-cored 7.62 mm × 51 mm bullet into a glass- faced polyurethane elastomeric polymer resin has been studied. The resulting craters in the resin contained elongated bullet core material that had a significant amount of porosity. A simple linear viscoelastic model was applied to AUTODYN-2D to describe the behaviour of the resin and numerical results of the penetration mechanism and depth-of-penetration appeared to match experimental observations well. Analysis of the high speed photography and a numerical model of this bullet penetrating a viscoelastic polymer showed that during the initial stages of penetration, the projectile is essentially turned inside out. Furthermore, the shape of the cavity was defined by the elastic relaxation of the polymer that led to compression of the core material. A weight analysis of the penetrated materials showed that using a thicker tile of glass resulted in better ballistic performanc

Multi-scale constitutive modeling of Ceramic Matrix Composites by Continuum Damage Mechanics

The microscale damage mechanisms in brittle ceramics are investigated in detail and a Continuum Damage Mechanics (CDM) model is developed in this work to study two common failure modes in Ceramic Matrix Composites (CMC), i.e. matrix/interphase fracture and fiber sliding. In order to empower the developed framework for performing crashworthiness studies, the effect of the dynamic energy density content on the microscale fracture modes of CMCs is also considered. The CDM model is developed within a physically consistent framework that includes basic fracture mechanics of CMCs. Also the CDM model is developed in such a way that most of the material parameters are directly obtainable form the experimental data rather than cumbersome and time consuming numerical curve fitting techniques. In order to construct a computationally effective multiscale analysis platform for CMCs, this work aims to provide an asymptotic solution for a microscale representative volume element (RVE) which represents the fiber, interphase and matrix interactions. The developed asymptotic solution can capture the non-linear response of CMCs through CDM model; and it considerably reduces the computational cost of hierarchical multiscale analysis in comparison to the numerical methods, e.g. numerical models that simulate the real microstructure. The CDM model and the RVE asymptotic solution are utilized to study the microscale damage mechanisms in CMC systems. It is shown that the developed scheme performs quite well in capturing available experiments in the literature and provides a comprehensive description of microscale damage mechanisms in CMCs. The developed framework can be utilized in the future developments of the hierarchical multiscale analysis of CMC systems