Competition between energy and dynamics in memory formation

Bi-stable objects that are pushed between states by an external field are often used as a simple model to study memory formation in disordered materials. Such systems, called hysterons, are typically treated quasistatically. Here, we generalize hysterons to explore the effect of dynamics in a simple spring system with tunable bistability and study how the system chooses a minimum. Changing the timescale of the forcing allows the system to transition between a situation where its fate is determined by following the local energy minimum to one where it is trapped in a shallow well determined by the path taken through configuration space. Oscillatory forcing can lead to transients lasting many cycles, a behavior not possible for a single quasistatic hysteron.Comment: 6 pages, 5 figures, 1 vide

Duke Research in Perspective: Trend of publications and interdisciplinarity of Duke's education and research

We investigate the trends in interdisciplinary research at Duke University using datasets provided by Scholars@Duke and The Graduate School. The data holds bibliographical information on faculty appointments, their publications (including abstracts and publication venues ), and faculty members of PhD dissertation committees for students completing their PhD degrees from 2012 to 2017. By looking at the total number of publications at Duke, we observe a descending trend over the course of five years in all schools except Duke Law School. We then look at the fraction of these publications that cross departmental and school boundaries. The results depict fluctuations over time in most cases; however some meaningful trends in the interdisciplinary research are observed . For instance, Institutes and Provost’s Academic Units , and Trinity College of Arts and Sciences have been showing an increase in the fraction of interdisciplinary publications despite the decrease in their total number of published papers. To see the overlap between schools, we look at the graphs of coauthorships between different organization/departments, and how PhD students in each department select their dissertation committee members from different schools. The School of Medicine , and Trinity College of Arts and Sciences are the leading schools with the largest number of publications and collaborations. By looking at these graphs we can see that School of Medicine has done an incredible job at crossing the boundaries and collaborating with almost all the other schools across Duke. The same two schools have the largest number of faculty who serve as dissertation committee members in all schools and departments across Duke

Transient learning degrees of freedom for introducing function in materials

The introduction of transient degrees of freedom into a system can lead to novel material design and training protocols that guide a system into a desired metastable state. In this approach, some degrees of freedom, which were not initially included in the system dynamics, are first introduced and subsequently removed from the energy minimization process once the desired state is reached. Using this conceptual framework, we create stable jammed packings that exist in exceptionally deep energy minima marked by the absence of low-frequency quasilocalized modes; this added stability persists in the thermodynamic limit. The inclusion of particle radii as transient degrees of freedom leads to deeper and much more stable minima than does the inclusion of particle stiffnesses. This is because particle radii couple to the jamming transition, whereas stiffnesses do not. Thus, different choices for the added degrees of freedom can lead to very different training outcomes