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All Articles in Statistical, Nonlinear, and Soft Matter Physics

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Collective Motion And Phase Diagram Of Self-Propelled Vibrated Hard Squares, Zhejun Shen 2022 University of Massachusetts Amherst

Collective Motion And Phase Diagram Of Self-Propelled Vibrated Hard Squares, Zhejun Shen

Doctoral Dissertations

In equilibrium, matter condenses into ordered phases due to the combined effects of inter-particle interactions and entropy. In this dissertation, we explore the self-propulsion of particles as an additional nonequilibrium consideration in the mechanisms for ordering. Our experiments employ square-shaped hard particles; in equilibrium, when particle motions are randomly directed, squares form entropically-stabilized phases in which first their orientations, and then their positions, get locked in relative to each other, depending on the density of coverage. When the square tiles are modified to have small propulsion along some body-fixed axis we find that their tendency to order is profoundly altered ...


The Interaction Of Topological Defects In Anisotropically-Elastic Nematic Liquid Crystals, Carter J. Swift 2022 Macalester College

The Interaction Of Topological Defects In Anisotropically-Elastic Nematic Liquid Crystals, Carter J. Swift

Macalester Journal of Physics and Astronomy

Topological defects are very well understood so long as the medium in which they exist is isotropically-elastic. They lead to director fields which are easy to calculate and superpose linearly so that a system with any number of defects is analytically treatable. They also have an interaction which is simple in form and can be accurately described by the Peach-Koehler force. In an anisotropically-elastic medium, however, such defects are very poorly understood outside of the single-defect case which was solved by Dzyaloshinskii. In this project, numerical and approximate analytical techniques are applied in order to better understand the interaction between ...


Discovering Reduced-Order Dynamical Models From Data, William Qian, Pratik A. Chaudhari 2022 University of Pennsylvania

Discovering Reduced-Order Dynamical Models From Data, William Qian, Pratik A. Chaudhari

Technical Reports (ESE)

This work explores theoretical and computational principles for data-driven discovery of reduced-order models of physical phenomena. We begin by describing the theoretical underpinnings of multi-parameter models through the lens of information geometry. We then explore the behavior of paradigmatic models in statistical physics, including the diffusion equation and the Ising model. In particular, we explore how coarse-graining a system affects the local and global geometry of a “model manifold” which is the set of all models that could be fit using data from the system. We emphasize connections of this idea to ideas in machine learning. Finally, we employ coarse-graining ...


Estimation Of Pure B Power In Polarized Cmb Data Via Gibbs Sampling., Joseph Sterling 2022 University of Richmond

Estimation Of Pure B Power In Polarized Cmb Data Via Gibbs Sampling., Joseph Sterling

Honors Theses

In the search for effective processes to estimate E and B spectra from polarized data, Gibbs Sampling has proven to be a powerful method. In the search for B modes, it is essential to avoid a false positive detection due to contamination from the larger E component. It is therefore of interest to combine Gibbs sampling with methods to “purify” the B modes, ensuring that a B-mode detection is robust. This goal can be achieved by compelling the Gibbs Sampler to estimate a pure B spectrum. The method we chose to implement involves an artificially inflated E spectrum, which “forces ...


Physics 516: Electromagnetic Phenomena (Spring 2022), Philip C. Nelson 2022 University of Pennsylvania

Physics 516: Electromagnetic Phenomena (Spring 2022), Philip C. Nelson

Department of Physics Papers

These course notes are made publicly available in the hope that they will be useful. All reports of errata will be gratefully received. I will also be glad to hear from anyone who reads them, whether or not you find errors: pcn@upenn.edu.


Modeling Chain Packing In Complex Phases Of Self-Assembled Block Copolymers, Anugu Abhiram Reddy 2022 University of Massachusetts Amherst

Modeling Chain Packing In Complex Phases Of Self-Assembled Block Copolymers, Anugu Abhiram Reddy

Doctoral Dissertations

Block copolymer (BCP) melts undergo microphase seperation and form ordered soft matter crystals with varying domain shapes and symmetries. We study the con- nection between diblock copolymer molecular designs and thermodynamic selection of ordered crystals by modeling features of variable sub-domain geometry filled with individual blocks within non-canonical sphere-like and network phases that together with layered, cylindrical and canonical spherical phases forms “natural forms” of self- assembled amphiphilic soft matter at large. First, we present a model to revise our understanding of optimal Frank-Kasper sphere-like morphologies by advancing the- ory to account for varying domain volumes. We then develop generic ...


Memory Capacity In A System Of Swelling Particles, David T. Keating 2022 California Polytechnic State University, San Luis Obispo

Memory Capacity In A System Of Swelling Particles, David T. Keating

Physics

A system has the ability to store memory if one is able to write, retrieve, and erase information from it. Some systems are capable of storing multiple transient memories; with no noise in these systems, at long time, the memories degrade until one or two remain. The addition of noise to these systems can extend the retention of multiple memories, in some cases indefinitely [2, 3]. While this behavior was first observed in simulations of charge density waves, it has since appeared in other systems [1].

Past research has shown that sheared non-Brownian liquid suspensions of particles exhibit similar behavior ...


A Microfluidic Approach For Synthesis And Kinetic Profiling Of Branched Gold Nanostructures, Qi Cai, Valentina Castagnola, Luca Boselli, Alirio Moura, Hender Lopez, Wei Zhang, João M. de Araújo, Kenneth A. Dawson 2022 University College Dublin

A Microfluidic Approach For Synthesis And Kinetic Profiling Of Branched Gold Nanostructures, Qi Cai, Valentina Castagnola, Luca Boselli, Alirio Moura, Hender Lopez, Wei Zhang, João M. De Araújo, Kenneth A. Dawson

Articles

Automatized approaches for nanoparticle synthesis and characterization represent a great asset to their applicability in the biomedical field by improving reproducibility and standardization, which help to meet the selection criteria of regulatory authorities. The scaled-up production of nanoparticles with carefully defined characteristics, including intrinsic morphological features, and minimal intra-batch, batch-to-batch, and operator variability, is an urgent requirement to elevate nanotechnology towards more trustable biological and technological applications. In this work, microfluidic approaches were employed to achieve fast mixing and good reproducibility in synthesizing a variety of gold nanostructures. The microfluidic setup allowed exploiting spatial resolution to investigate the growth evolution ...


Numerical Treatment For Special Type Of Mixed Linear Delay Volterra Integro-Differential Equations, Atheer J. Kadhim 2022 University of Technology,Iraq

Numerical Treatment For Special Type Of Mixed Linear Delay Volterra Integro-Differential Equations, Atheer J. Kadhim

Emirates Journal for Engineering Research

The idea of research is a representation of the nonlinear pseudo-random generators using state-space equations that is not based on the usual description as shift register synthesis but in terms of matrices. Different types of nonlinear pseudo-random generators with their algorithms have been applied in order to investigate the output pseudo-random sequences. Moreover, two examples are given for conciliated the results of this representation.


Charge Transport And Spin Dynamics Of Color Centers In Diamond, Damon Daw 2022 The Graduate Center, City University of New York

Charge Transport And Spin Dynamics Of Color Centers In Diamond, Damon Daw

Dissertations, Theses, and Capstone Projects

Solid state defects in diamond are promising candidates for room temperature quantum information processors (1, 3, 5). Chief among these defects is the nitrogen vacancy center (‘NV center’ or ‘NV’). The NV has long coherence times (at 300K) and its state is easily initialized, manipulated and read out (5). However, the outstanding issue of entangling NV centers in a scalable fashion, at room temperature remains a challenge. This thesis presents experimental and theoretical work aimed at achieving this goal by developing the ‘flying qubit’ framework in (1). This method for remote entanglement utilizes a charge carrier (initialized into a definite ...


Generally Covariant Theory Of Multipole Moment Conserving Quasiparticles, Gavin Eric Riley 2022 University of New Hampshire

Generally Covariant Theory Of Multipole Moment Conserving Quasiparticles, Gavin Eric Riley

Honors Theses and Capstones

This report represents the creation of a field theory which is capable of describing quasiparticle excitations that preserve 2^k -pole moments. These quasiparticles exhibit certain ’semidynamic’ properties such as individual particle immobility but free movement of bound 2^L-tuples. We provide a review of work done on dipole conserving fractons and their dynamics [1] and expand upon it to describe higher moment conserving systems with global quadratic (and higher) phase symmetry. This requires the selection of the temporal and spatial directions. The selection of a temporal direction is done with a foliation defined by an anisotropic scaling of space ...


A Surrogate Model Of Molecular Dynamics Simulations For Polar Fluids: Supervised Learning Methods For Molecular Polarization And Unsupervised Methods For Phase Classification, Zackerie W. Hjorth 2022 Michigan Technological University

A Surrogate Model Of Molecular Dynamics Simulations For Polar Fluids: Supervised Learning Methods For Molecular Polarization And Unsupervised Methods For Phase Classification, Zackerie W. Hjorth

Dissertations, Master's Theses and Master's Reports

Molecular Dynamic (MD) simulation is a standard computational tool in soft matter physics. While very powerful, it is computationally expensive, leading to some simulations taking days or even weeks to complete depending on the size of your computer cluster. Finding computationally cheap surrogate models which can learn the output features of MD simulation is therefore highly motivated. In this report I explore the use of deep neural network ensembles as well as support vector machine regressors as surrogate models for MD simulation. From the output of the surrogate models, we can then employ unsupervised learning methods to get insight into ...


Model Checks For Two-Sample Location-Scale, Atefeh Javidialsaadi 2021 New Jersey Institute of Technology

Model Checks For Two-Sample Location-Scale, Atefeh Javidialsaadi

Dissertations

Two-sample location-scale refers to a model that permits a pair of standardized random variables to have a common distribution. This means that if X1 and X2 are two random variables with means µ1 and µ2 and standard deviations ?1 and ?2, then (X1 - µ1)/?1 and (X2 - µ2)/?2 have some common unspecified standard or base distribution F0. Function-based hypothesis testing for these models refers to formal tests that would help determine whether or not two samples may have come from some location-scale family of distributions, without specifying the standard distribution ...


A Nanoscale Shape-Discovery Framework Supporting Systematic Investigations Of Shape-Dependent Biological Effects And Immunomodulation, Wei Zhang, Hender Lopez, Luca Boselli, Paolo Bigini, André Perez-Potti, Zengchun Xie, Valentina Castagnola, Qi Cai, Camila P. Silveira, Joao M. de Araujo, Laura Talamini, Nicolò Panini, Giuseppe Ristagno, Martina B. Violatto, Stéphanie Devineau, Marco P. Monopoli, Mario Salmona, Valeria A. Giannone, Sandra Lara, Kenneth A. Dawson, Yan Yan 2021 University College Dublin

A Nanoscale Shape-Discovery Framework Supporting Systematic Investigations Of Shape-Dependent Biological Effects And Immunomodulation, Wei Zhang, Hender Lopez, Luca Boselli, Paolo Bigini, André Perez-Potti, Zengchun Xie, Valentina Castagnola, Qi Cai, Camila P. Silveira, Joao M. De Araujo, Laura Talamini, Nicolò Panini, Giuseppe Ristagno, Martina B. Violatto, Stéphanie Devineau, Marco P. Monopoli, Mario Salmona, Valeria A. Giannone, Sandra Lara, Kenneth A. Dawson, Yan Yan

Articles

Since it is now possible to make, in a controlled fashion, an almost unlimited variety of nanostructure shapes, it is of increasing interest to understand the forms of biological control that nanoscale shape allows. However, a priori rational investigation of such a vast universe of shapes appears to present intractable fundamental and practical challenges. This has limited the useful systematic investigation of their biological interactions and the development of innovative nanoscale shape-dependent therapies. Here, we introduce a concept of biologically relevant inductive nanoscale shape discovery and evaluation that is ideally suited to, and will ultimately become, a vehicle for machine ...


Towards Long Term Colloid Suspension In A Vertically Rotated System., Md Mahmudur Rahman 2021 University of Louisville

Towards Long Term Colloid Suspension In A Vertically Rotated System., Md Mahmudur Rahman

Electronic Theses and Dissertations

Within a colloidal suspension gravity may compromise the observation of governing physical interactions, especially those that are weak and/or take significant time to develop. Conducting the experiment in a long-term microgravity environment is a viable option to negate gravitational effects, though significant resources are required to do so. While it may not be possible to simulate long-term microgravity terrestrially, particles can resist quick sedimentation in a confined suspension system rotating vertically with appropriate rotation speed. The goal of the investigation is to demonstrate the existence of long-term particle suspension regime for a certain colloidal suspension while characterizing colloidal behavior ...


Swarming Oscillators With Time-Delayed Interactions, Nicholas S. Blum 2021 California Polytechnic State University, San Luis Obispo

Swarming Oscillators With Time-Delayed Interactions, Nicholas S. Blum

Physics

We investigate the role of delay in the collective dynamics of particles that swarm in space and possess an internal oscillatory degree of freedom, called swarmalators. Swarmalators were introduced recently by O’Keeffe, Hong, and Strogatz in Nature Communications 8, 1504 (2017). The addition of a time delay into the system of swarmalators was motivated by the biology of early embryonic development. This delay leads to a rich phenomenology, which includes two new collective states, which we call "semi-static crystal" and "boiling". In the semi-static crystal state, all particles in a cluster undergo decaying radial oscillations completely in phase with ...


Pattern Formation And Phase Transition Of Connectivity In Two Dimensions, Arman Mohseni Kabir 2021 University of Massachusetts Amherst

Pattern Formation And Phase Transition Of Connectivity In Two Dimensions, Arman Mohseni Kabir

Doctoral Dissertations

This dissertation is devoted to the study and analysis of different types of emergent behavior in physical systems. Emergence is a phenomenon that has fascinated researchers from various fields of science and engineering. From the emergence of global pandemics to the formation of reaction-diffusion patterns, the main feature that connects all these diverse systems is the appearance of a complex global structure as a result of collective interactions of simple underlying components. This dissertation will focus on two types of emergence in physical systems: emergence of long-range connectivity in networks and emergence and analysis of complex patterns.

The most prominent ...


Robust Method Of Determining Microfacet Brdf Parameters In The Presence Of Noise Via Recursive Optimization, Michael W. Bishop, Samuel D. Butler, Michael A. Marciniak 2021 Air Force Institute of Technology

Robust Method Of Determining Microfacet Brdf Parameters In The Presence Of Noise Via Recursive Optimization, Michael W. Bishop, Samuel D. Butler, Michael A. Marciniak

Faculty Publications

Accurate bidirectional reflectance distribution function (BRDF) models are essential for computer graphics and remote sensing performance. The popular microfacet class of BRDF models is geometric-optics-based and computationally inexpensive. Fitting microfacet models to scatterometry measurements is a common yet challenging requirement that can result in a model being fit as one of several unique local minima. Final model fit accuracy is therefore largely based on the quality of the initial parameter estimate. This makes for widely varying material parameter estimates and causes inconsistent performance comparisons across microfacet models, as will be shown with synthetic data. We proposed a recursive optimization method ...


Wave Excitation And Dynamics In Disordered Systems, Yiming Huang 2021 The Graduate Center, City University of New York

Wave Excitation And Dynamics In Disordered Systems, Yiming Huang

Dissertations, Theses, and Capstone Projects

This thesis presents studies of the field and energy excited in disordered systems as well as the dynamics of scattering.

Dynamic and steady state aspects of wave propagation are deeply connected in lossless open systems in which the scattering matrix is unitary. There is then an equivalence among the energy excited within the medium through all channels, the Wigner time delay, which is the sum of dwell times in all channels coupled to the medium, and the density of states. But these equivalences fall away in the presence of material loss or gain. In this paper, we use microwave measurements ...


Nonlinear Optical Studies Of Interfacial Ferroelectricity And Strain Distribution In Perovskite Dielectric Films, Tony Le 2021 The Graduate Center, City University of New York

Nonlinear Optical Studies Of Interfacial Ferroelectricity And Strain Distribution In Perovskite Dielectric Films, Tony Le

Dissertations, Theses, and Capstone Projects

Dielectric and ferroelectric perovskite films have been model energy storage structures for their low-dielectric loss, extremely high charge-discharge speed, and good temperature stability, yet there is still much to understand about the material’s limitations. This dissertation presents a detailed understanding of the strain-induced ferroelectricity at the boundary between a strontium titanate (SrTiO3) ultrathin film epitaxially grown on a germanium (Ge) substrate through optical second harmonic generation (SHG), and the polydomain distribution in the Zr-doped BaTiO3 (BZT) films by time-resolved pump-probe spectroscopy.

First, SHG measurements were performed to reveal interfacial ferroelectricity in the epitaxial SrTiO3/Ge (100 ...


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