arXiv subjects

Scott V. Franklin

Publications and source records attributed to Scott V. Franklin.

16 recordsLinked to original sources

arXiv2023

Emerging Physics Education Researchers' Growth in Professional Agency: Case Study

Improving the physics enterprise to broaden participation in physics is one of the main goals of the physics education research community. Many classically trained physics faculty transition during their faculty career into engaging in research investigating the teaching and learning of their discipline. There is scarce research on the support and needs of these faculty as they engage in their first projects in this new research field for them. We investigate agency growth of two emerging physics education researchers and one emerging mathematics education researcher as they participate in a professional development program. We ground our case study analysis of interview data in a theoretical framework on agency. We identify the elements of the professional development program that were transformative in our case study participants' trajectory in education research. Receiving get-started information, building mechanisms to sustain research projects and engaging with a supportive community help participants transform general interests to specific questions, articulate concrete next-steps and increase their sense of self-efficacy. During this professional development program all three case study participants gain agency in this new area of research for them. These identified program elements that affect agency growth can inform professional development opportunities for faculty transitioning into discipline-based education research, which expands our understanding of how to build capacity in the field.

physics.ed-ph↗

arXiv2022

Properties of packings and dispersions of superellipse sector particles

Superellipse sector particles (SeSPs) are segments of superelliptical curves that form a tunable set of hard-particle shapes for granular and colloidal systems. SeSPs allow for continuous parameterization of corner sharpness, aspect ratio, and particle curvature; rods, circles, rectangles, and staples are examples of shapes SeSPs can model. We compare three computational processes: pair-wise Monte Carlo simulations that look only at particle-particle geometric constraints, Monte Carlo simulations that look at how these geometric constraints play out over extended dispersions of many particles, and Molecular Dynamics simulations that allow particles to interact to form random loose and close packings. We investigate the dependence of critical random loose and close packing fractions on particle parameters, finding that both values tend to increase with opening aperture (as expected) and, in general, decrease with increasing corner sharpness. The identified packing fractions are compared with the mean-field prediction of the Random Contact Model. We find deviations from the model's prediction due to correlations between particle orientations. The complex interaction of spatial proximity and orientational alignment is explored using a generalized Spatio-Orientational Distribution Area (SODA) plot. Higher density packings are achieved through particles assuming a small number of preferred configurations which depend sensitively on particle shape and system preparation.

cond-mat.soft↗

arXiv2021

The Excluded Area of Superellipse Sector Particles

Superellipse sector particles (SeSPs) are segments of superelliptical curves that form a tunable set of hard-particle shapes for granular and colloidal systems. SeSPs allow for continuous parameterization of corner sharpness, aspect ratio, and particle curvature; rods, circles, rectangles, and staples are examples of shapes SeSPs can model. We investigate the space of allowable (non-overlapping) configurations of two SeSPs, which depends on both the center-of-mass separation and relative orientation. Radial correlation plots of the allowed configurations reveal circular regions centered at each of the particle's two endpoints that indicate configurations of mutually-entangled particle interactions. Simultaneous entanglement with both endpoints is geometrically impossible; the overlap of these two regions therefore represents an excluded area in which no particles can be placed regardless of orientation. The regions' distinct boundaries indicates a translational frustration with implications for the dynamics of particle rearrangements (e.g. under shear). Representing translational and rotational degrees of freedom as a hypervolume, we find a topological change that suggests geometric frustration arises a phase transition in this space. The excluded area is a straightforward integration over excluded states; for arbitrary relative orientation this decreases sigmoidally with increasing opening aperture, with sharper SeSP corners resulting in a sharper decrease. Together, this work offers a path towards a unified theory for particle shape-control of bulk material properties.

cond-mat.soft↗

arXiv2019

Random packing of rods in small containers

We conduct experiments and simulations to study the disordered packing of rods in small containers. Experiments study cylindrical rods with aspect ratio ranging from 4 to 32; simulations use of spherocylinders with similar aspect ratios. In all cases, rods pack randomly in cylindrical containers whose smallest dimension is larger than the rod length. Packings in smaller containers have lower volume fractions than those in larger containers, demonstrating the influence of the boundaries. The volume fraction extrapolated to infinite container size decreases with increasing aspect ratio, in agreement with previous work. X-ray tomography experiments show that the boundary effects depend on the orientation of the boundary, indicating a strong influence of gravity, whereas the simulation finds boundary effects that are purely geometric. In all cases, the boundary influence extends approximately half a particle length into the interior of the container.

cond-mat.soft↗

arXiv2017

Using Social Network Analysis on classroom video data

We propose a novel application of Social Network Analysis (SNA) using classroom video data as a means of quantitatively and visually exploring the collaborations between students. The context for our study was a summer program that works with first generation students and deaf/hard-of-hearing students to engage in authentic science practice and develop a supportive community. We applied SNA to data from one activity during the two-week program to test our approach and as a means to begin to assess whether the goals of the program are being met. We used SNA to identify groups that were interacting in unexpected ways and then to highlight how individuals were contributing to the overall group behavior. We plan to expand our new use of SNA to video data on a larger scale.

physics.ed-ph↗

arXiv2017

Guided and Unguided Student Reflections

Self-reflection is important metacognitive skill, enabling students to build coherence into their learning and embed content in a broader context. While various pedagogical techniques exist to encourage student reflection, little research has examined the differences between formally guided, partially guided and unguided reflections. This study focuses on student responses to online Guided Reflection Forms (GRFs) from students in a first-semester non-physics class and, separately, a sophomore-level Vibrations \& Waves course for physics majors, and compares these guided reflections with partially guided and unguided journals from a STEM enrichment summer program for incoming college students. A previously developed coding scheme was used on guided reflections and the {\bf LIWC} computational linguistics tool used to confirm the distinct nature of the categories. A new coding scheme was created and validated for the unguided journals. We find that both guided and unguided reflections elicit metacognitive and reflective practice, although of measurably different frequencies and kinds.

physics.ed-ph↗

arXiv2015

Compression- and Shear-Driven Jamming of U-Shaped Particles in Two Dimensions

We carry out numerical simulations of soft, U-shaped, frictionless particles in $d=2$ dimensions in order to explore the effects of complex particle shape on the jamming transition. We consider both cases of uniform compression-driven and shear-driven jamming as packing fraction $ϕ$ and compression or shear rate is varied. Upon slow compression, jamming is found to occur when the isostatic condition is satisfied. Under driven steady state shearing, jamming occurs at a higher packing fraction $ϕ_J$ than observed in compression. A growing relaxation time and translational correlation length is found as $ϕ$ increases towards $ϕ_J$. We consider the orientational ordering and rotation of particles induced by the shear flow. Both nematic and tetratic ordering are found, but these decrease as $ϕ$ increases to $ϕ_J$. At the jamming transition, the nematic ordering further decreases, while the tetratic ordering increases, but the orientational correlation lengths remain small throughout. The average angular velocity of the particles is found to increase as $ϕ$ increases, saturating to a plateau just below $ϕ_J$, but then increasing again as $ϕ$ increases above $ϕ_J$.

cond-mat.soft↗

arXiv2014

Dynamic facilitation observed near the colloidal glass transition

We present experimental confirmation of dynamic facilitation in monodisperse and bidisperse colloidal suspensions near the glass transition volume fraction. Correlations in particle dynamics are seen to exist not only in space (clusters and strings) but also as bubbles in space-time. Quantitatively, highly mobile particles are more likely (than immobile particles) to have nearest neighbors that were highly mobile in immediately preceding times. The interpretation is that a particle's mobility enables or facilitates the subsequent motion of its neighbors. Facilitation is most pronounced at the relaxation time that corresponds with cage-breaking, when dynamic heterogeneity is also maximized.

cond-mat.soft↗

arXiv2012

Entangled granular media

We study the geometrically induced cohesion of ensembles of granular "u-particles" which mechanically entangle through particle interpenetration. We vary the length-to-width ratio $l/w$ of the u-particles and form them into free-standing vertical columns. In laboratory experiment we monitor the response of the columns to sinusoidal vibration (frequency $f$, peak acceleration $Γ$). Column collapse occurs in a characteristic time, $τ$, which follows the relation $τ= f^{-1} \exp(Δ/ Γ)$. $Δ$ resembles an activation energy and is maximal at intermediate $l/w$. Simulation reveals that optimal strength results from competition between packing and entanglement.

cond-mat.soft↗

arXiv2010

Fluctuations in Student Understanding of Newton's 3rd Law

We present data from a between-student study on student response to questions on Newton's Third Law given throughout the academic year. The study, conducted at Rochester Institute of Technology, involved students from the first and third of a three-quarter sequence. Construction of a response curve reveals subtle dynamics in student learning not captured by simple pre/post testing. We find a a significant positive effect from direct instruction, peaking at the end of instruction on forces, that diminishes by the end of the quarter. Two quarters later, in physics III, a significant dip in correct response occurs when instruction changes from the vector quantities of electric forces and fields to the scalar quantity of electric potential. Student response rebounds to its initial values, however, once instruction returns to the vector-based topics involving magnetic fields.

physics.ed-ph↗

arXiv2010

Spatial and temporal dynamical heterogeneities approaching the binary colloidal glass transition

We study concentrated binary colloidal suspensions, a model system which has a glass transition as the volume fraction $ϕ$ of particles is increased. We use confocal microscopy to directly observe particle motion within dense samples with $ϕ$ ranging from 0.4 to 0.7. Our binary mixtures have a particle diameter ratio $d_S/d_L=1/1.3$ and particle number ratio $N_S/N_L=1.56$, which are chosen to inhibit crystallization and enable long-time observations. Near the glass transition we find that particle dynamics are heterogeneous in both space and time. The most mobile particles occur in spatially localized groups. The length scales characterizing these mobile regions grow slightly as the glass transition is approached, with the largest length scales seen being $\sim 4$ small particle diameters. We also study temporal fluctuations using the dynamic susceptibility $χ_4$, and find that the fluctuations grow as the glass transition is approached. Analysis of both spatial and temporal dynamical heterogeneity show that the smaller species play an important role in facilitating particle rearrangements. The glass transition in our sample occurs at $ϕ_g \approx 0.58$, with characteristic signs of aging observed for all samples with $ϕ>ϕ_g$.

cond-mat.soft↗

arXiv2010

Column collapse of granular rods

We find the collapse of columns of granular rods to show range of behaviors that depends on particle aspect ratio (length $L$ to diameter $d$) and initial pile geometry (height/radius). For all aspect ratios $L/d$ below 24 there exists a critical height at $L/4$ below which the pile acts as a solid, maintaining its initial shape, and a second critical height at $3L/4$ above which the pile always collapses like an ordinary granular material. Separating the critical heights is a transition region in which the probability of collapse increases linearly from 0 to 1. This behavior is independent of particle length, width, or aspect ratio. When the pile does collapse, the runoff radius $r_f$ scales as a power-law with dimensionless height $\tilde H$, agreeing with previous experiments on ordinary sand. For low piles the scaling is linear, with $r_f\sim \tilde H^{1.2\pm 0.1}$. Above a critical pile aspect ratio (pile height/radius) this switches to a square-root scaling, with $H^{0.6\pm0.1}$.

cond-mat.soft↗

arXiv2006

Realizing a New Research Agenda for Writing-to-Learn: Embedding Process in Context

Writing-to-learn initiatives such as Writing Across the Curriculum or Writing in the Disciplines occupy the center of writing programs nationwide. Nevertheless, research to support the core of the writing-to-learn philosophy--that the writing process can facilitate content learning--is, at best, inconclusive. Calls for additional research have noted the importance of either additional cognitive analyses or new contextual research methods. This paper argues for a unique research agenda that would embed cognitive processes into disciplinary contexts and thus provide a layered, multi-modal research approach into writing and learning.

physics.ed-ph↗

arXiv2006

Assessing the Impact of Student Learning Style Preferences

Students express a wide range of preferences for learning environments. We are trying to measure the manifestation of learning styles in various learning environments. In particular, we are interested in performance in an environment that disagrees with the expressed learning style preference, paying close attention to social (group vs. individual) and auditory (those who prefer to learn by listening) environments. These are particularly relevant to activity-based curricula which typically emphasize group-work and de-emphasize lectures. Our methods include multiple-choice assessments, individual student interviews, and a study in which we attempt to isolate the learning environment.

physics.ed-ph↗

arXiv2006

Two-dimensional Packing in Prolate Granular Materials

We investigate the two-dimensional packing of extremely prolate (aspect ratio $α=L/D>10$) granular materials, comparing experiments with Monte-Carlo simulations. The average packing fraction of particles with aspect ratio $α=12$ is $0.68\pm0.03$. We quantify the orientational correlation of particles and find a correlation length of two particle lengths. The functional form of the decay of orientational correlation is the same in both experiments and simulations spanning three orders of magnitude in aspect ratio. This function decays over a distance of two particle lengths. It is possible to identify voids in the pile with sizes ranging over two orders of magnitude. The experimental void distribution function is a power law with exponent $-β=-2.43\pm0.08$. Void distributions in simulated piles do not decay as a power law, but do show a broad tail. We extend the simulation to investigate the scaling at very large aspect ratios. A geometric argument predicts the pile number density to scale as $α^{-2}$. Simulations do indeed scale this way, but particle alignment complicates the picture, and the actual number densities are quite a bit larger than predicted.

cond-mat.soft↗

arXiv2006

Jamming of 3D Prolate Granular Materials

We have found that the ability of long thin rods to jam into a solid-like state in response to a local perturbation depends upon both the particle aspect ratio and the container size. The dynamic phase diagram in this parameter space reveals a broad transition region separating granular stick-slip and solid-like behavior. In this transition region the pile displays both solid and stick-slip behavior. We measure the force on a small object pulled through the pile, and find the fluctuation spectra to have power law tails with an exponent characteristic of the region. The exponent varies from $β=-2$ in the stick-slip region to $β=-1$ in the solid region. These values reflect the different origins -- granular rearrangements vs. dry friction -- of the fluctuations. Finally, the packing fraction shows only a slight dependence on container size, but depends on aspect ratio in a manner predicted by a mean field theory and implies an aspect-ratio independent contact number of $ = 5.25 \pm 0.03$.

cond-mat.soft↗