Vibrated Squares As Equilibrium And Active Matter, 2018 University of Massachusetts Amherst
Vibrated Squares As Equilibrium And Active Matter, Lee Askew Walsh
We study the effects of particle shape and self-propulsion on the collective behaviors of a two-dimensional granular fluid, using an experimental system of hard square grains. We energize the system by vibration, which, depending on particle shape, induces either isotropic diffusion or persistent self-propulsion in the particles. We use specially designed grains as a model system to study (i) the equilibrium packing of hard squares in two dimensions, (ii) the dynamics of athermal self-propelled particles, and (iii) the melting kinetics of an unconfined granular crystallite.
The first study concerns the phase diagram of a two-dimensional fluid of hard squares, which ...
Statistical Biophysics Blog: Let’S Stop Being Sloppy About Uncertainty, 2017 Oregon Health & Science University
Statistical Biophysics Blog: Let’S Stop Being Sloppy About Uncertainty, Daniel M. Zuckerman
Molecular dynamics simulations often fail to reach timescales characteristic of equilibrum sampling, so great care must be taken in computing and reporting statistical uncertainty.
Weak-Value Amplification And Optimal Parameter Estimation In The Presence Of Correlated Noise, 2017 University of Toronto
Weak-Value Amplification And Optimal Parameter Estimation In The Presence Of Correlated Noise, Josiah Sinclair, Matin Hallaji, Aephraim M. Steinberg, Jeff Tollaksen, Andrew N. Jordan
Mathematics, Physics, and Computer Science Faculty Articles and Research
We analytically and numerically investigate the performance of weak-value amplification (WVA) and related parameter estimation methods in the presence of temporally correlated noise. WVA is a special instance of a general measurement strategy that involves sorting data into separate subsets based on the outcome of a second “partitioning” measurement. Using a simplified correlated noise model that can be analyzed exactly together with optimal statistical estimators, we compare WVA to a conventional measurement method. We find that WVA indeed yields a much lower variance of the parameter of interest than the conventional technique does, optimized in the absence of any partitioning ...
Dynamic Self-Assembly And Self-Organized Transport Of Magnetic Micro-Swimmers, 2017 Argonne National Laboratory
Dynamic Self-Assembly And Self-Organized Transport Of Magnetic Micro-Swimmers, Gašper Kokot, German Kolmakov V, Igor S. Aranson, Alexey Snezhko
Publications and Research
We demonstrate experimentally and in computer simulations that magnetic microfloaters can self-organize into various functional structures while energized by an external alternating (ac) magnetic field. The structures exhibit self-propelled motion and an ability to carry a cargo along a pre-defined path. The morphology of the self-assembled swimmers is controlled by the frequency and amplitude of the magnetic field.
Discrete Space-Time Model For Heat Conduction: Application To Sizedependent Thermal Conductivity In Nano-Films, 2017 Institute of problems of Chemical Physics, Russia
Discrete Space-Time Model For Heat Conduction: Application To Sizedependent Thermal Conductivity In Nano-Films, Sergey Sobolev
No abstract provided.
Interface Propagation And Nucleation Phenomena For Discontinuous Poisoning Transitions In Surface-Reaction Models, James W. Evans, T. R. Ray
James W. Evans
Here, we consider discontinuous nonequilibrium phase transitions to poisoned or ‘‘adsorbing’’ states in lattice-gas models of surface reactions. Specifically, we examine the monomer or CO-poisoning transition in the Ziff-Gulari-Barshad monomer-dimer reaction model for CO oxidation, modified to include adspecies diffusion. For CO pressures below the poisoning transition, we first characterize the propagation of and fluctuations at an interface between reactive and CO-poisoned states. Here, we utilize ideas from spatial contact models, reaction-diffusion theory, and kinetic roughening theory. Evolution is described by the Kardar-Parisi-Zhang equation, but with the nonlinearity and kinetic surface tension vanishing on approaching the transition. Next, again for ...
Kinetics Of The Monomer-Monomer Surface Reaction Model, 2017 Iowa State University
Kinetics Of The Monomer-Monomer Surface Reaction Model, James W. Evans, T. R. Ray
James W. Evans
The two-dimensional monomer-monomer (AB) surface reaction model without diffusion is considered for infinitesimal, finite, and infinite reaction rates k. For equal reactant adsorption rates, in all cases, simulations reveal the same form of slow poisoning, associated with clustering of reactants. This behavior is also the same as that found in simulations of the two-dimensional voter model studied in interacting-particle systems theory. The voter model can also be obtained from the dimer-dimer or monomer-dimer surface reaction models with infinitesimal reaction rate. We provide a detailed elucidation of the slow poisoning kinetics via an analytic treatment for the k=0+ AB reaction ...
Interplay Of Quantum Size Effect, Anisotropy And Surface Stress Shapes The Instability Of Thin Metal Films, 2017 Western Kentucky University
Interplay Of Quantum Size Effect, Anisotropy And Surface Stress Shapes The Instability Of Thin Metal Films, Mikhail Khenner
Planar Granular Shear Flow Under External Vibration, 2017 Bucknell University
Planar Granular Shear Flow Under External Vibration, Brian Utter, Eric P. Hoppmann
Faculty Journal Articles
We present results from a planar shear experiment in which a two-dimensional horizontal granular assembly of pentagonal particles sheared between two parallel walls is subjected to external vibration. Particle tracking and photoelastic measurements are used to quantify both grain scale motion and interparticle stresses with and without imposed vibrations. We characterize the particle motion in planar shear and find that flow of these strongly interlocking particles consists of transient vortex motion with a mean flow given by the sum of exponential profiles imposed by the shearing walls. Vibration is applied either through the shearing surface or as bulk vertical vibration ...
Theory Of Helicoids And Skyrmions In Confined Cholesteric Liquid Crystals, 2017 Selected Works
Theory Of Helicoids And Skyrmions In Confined Cholesteric Liquid Crystals, Sajedeh Afghah, Jonathan Selinger
Determining The Grain Size Of Polycrystalline Diamond For High Energy Density Experiments, 2017 Northwestern University
Determining The Grain Size Of Polycrystalline Diamond For High Energy Density Experiments, Lauren Barmore
Undergraduate Research and Arts Exposition
The High Energy Density Sciences group at SLAC National Accelerator Laboratory uses shock waves produced by the Linac Coherent Light Source to dynamically compress polycrystalline diamond samples. Compressing these polycrystalline samples allows us to use x-ray diffraction to study the changes to the structure as it experiences high pressure conditions. Polycrystalline diamond is valuable to study because it can be formed into ablator capsules for use in inertial confinement fusion reactions. As a result of the shock compression, the polycrystalline diamond samples undergo dynamic compression, a combination of stress and strain. To understand how dynamic compression takes place in a ...
Statistical Biophysics Blog: What I Have Against (Most) Pmf Calculations, 2017 Oregon Health & Science University
Statistical Biophysics Blog: What I Have Against (Most) Pmf Calculations, Daniel M. Zuckerman
The potential of mean force (PMF) is one of the most widely used characterizations of a biomolecular system computed from simulation, but calculating and interpreting a PMF both present challenges.
Overview Of Weighted Ensemble Simulation: Path-Sampling, Steady States, Equilibrium, 2017 Oregon Health & Science University
Overview Of Weighted Ensemble Simulation: Path-Sampling, Steady States, Equilibrium, Daniel M. Zuckerman
A concise overview of the weighted ensemble path sampling method for rare events is given, aimed at beginners.
Effective Temperature In Nonequilibrium State With Heat Flux Using Discrete Variable Model, 2017 Institute of problems of Chemical Physics, Russia
Effective Temperature In Nonequilibrium State With Heat Flux Using Discrete Variable Model, Sergey Sobolev
Accuracy And Stability Of Integration Methods For Neutrino Transport In Core Collapse Supernovae, Kyle A. Gregory
University of Tennessee Honors Thesis Projects
No abstract provided.
Modeling Out-Of-Plane Actuation In Thin-Film Nematic Polymer Networks: From Chiral Ribbons To Auto-Origami Boxes Via Twist And Topology, Vianney Gimenez-Pinto, Fangfu Ye, Badel Mbanga, Jonathan Selinger, Robin Selinger
Effect Of Interstitial Fluid On The Fraction Of Flow Microstates That Precede Clogging In Granular Hoppers, 2017 University of Pennsylvania
Effect Of Interstitial Fluid On The Fraction Of Flow Microstates That Precede Clogging In Granular Hoppers, Juha Koivisto, Douglas J. Durian
Department of Physics Papers
We report on the nature of flow events for the gravity-driven discharge of glass beads through a hole that is small enough that the hopper is susceptible to clogging. In particular, we measure the average and standard deviation of the distribution of discharged masses as a function of both hole and grain sizes. We do so in air, which is usual, but also with the system entirely submerged under water. This damps the grain dynamics and could be expected to dramatically affect the distribution of the flow events, which are described in prior work as avalanche-like. Though the flow is ...
Universal Slip Dynamics In Metallic Glasses And Granular Matter – Linking Frictional Weakening With Inertial Effects, Dmitri V. Denisov, Kinga A. Lorincz, Wendelin J. Wright, Todd C. Hufnagel, Aya Nawano, Xiaojun Gu, Jonathan T. Uhl, Karin A. Dahmen, Peter Schall
Faculty Journal Articles
Slowly strained solids deform via intermittent slips that exhibit a material-independent critical size distribution. Here, by comparing two disparate systems - granular materials and bulk metallic glasses - we show evidence that not only the statistics of slips but also their dynamics are remarkably similar, i.e. independent of the microscopic details of the material. By resolving and comparing the full time evolution of avalanches in bulk metallic glasses and granular materials, we uncover a regime of universal deformation dynamics. We experimentally verify the predicted universal scaling functions for the dynamics of individual avalanches in both systems, and show that both the ...
Code For "Noise-Enhanced Coding In Phasic Neuron Spike Trains", 2017 Virginia Commonwealth University
Code For "Noise-Enhanced Coding In Phasic Neuron Spike Trains", Cheng Ly, Brent D. Doiron
Statistical Sciences and Operations Research Data
This zip file contains Matlab scripts and ode (XPP) files to calculate the statistics of the models in "Noise-Enhanced Coding in Phasic Neuron Spike Trains". This article is published in PLoS ONE.
Morphology Of Thin Sheets In The Lame Setup And Beyond, 2017 University of Massachusetts - Amherst
Morphology Of Thin Sheets In The Lame Setup And Beyond, Zhanlong Qiu
We present a general analytical approach to study the wrinkling phenomena in the Lame, sheet on drop, drop on sheet, and twisted ribbon setups. In the partially single-mode wrinkle pattern, we employ the boundary layer analysis to regularize the divergence in the energy and obtain the optimal wavenumber. In the multi-mode wrinkle pattern scenario, we consider the effects of the boundary condition, meniscus, and the geometry of the setup separately on the energies and obtain scaling results for the wavenumber of the multi-mode pattern due to each effect. Lastly, a wrinkle-to-fold transition is discussed in the Lame setup, with our ...