Physical Sciences and Mathematics Commons^™

The Timing Of Dynamical Interactions Between Planets In Exoplanetary Systems, David Robert Rice

UNLV Theses, Dissertations, Professional Papers, and Capstones

During the late stage of planet formation, a system is often dynamically packed with protoplanets. These bodies collide together and are ejected from the system to form the final planets. The duration of stability before these dynamical interactions occur is dependent on the initial separation of the bodies in a system. Previous works have shown that the time before a planet-planet close encounter is exponential with the initial planet spacing measured in units of mutual Hill radius. We investigate the limitations of these previous studies. We find that systems that are initially similar can have larger differences in stability times …

Dynamic Inventory Routing Optimization Based On Deep Reinforcement Learning, Jianpin Zhou, Shuliu Zhang

Journal of System Simulation

Abstract: Aiming at the dynamic stochastic inventory routing problem with periodic fluctuation of demand, a novel simulation optimization approach based on deep reinforcement learning is proposed to achieving periodic steady strategy. Firstly a dynamic combinatorial optimization model is constructed. Then, by deep reinforcement learning and setting heuristic rules, the replenishment nodes set selection and the replenishment batch allocation weights in each period are determined. The simulation experimental results show that the proposed method can improve the average profit of a cycle by about 2.7% and 3.9% in low fluctuating demand case and by about 8.2% and 7.1% in high fluctuating …

The Dynamics And Speciation Of Arsenic In Drinking Water Wells In Eastern Wisconsin, Evvan Plank

Theses and Dissertations

Arsenic typically develops in Eastern Wisconsin groundwater as a result of oxidation of sulfide bearing minerals in the limestone bedrock (Schreiber et al. 2000). Naturally occurring arsenic exists in groundwater as oxyanions which have two oxidation states, As(III) and As(V). Under ambient pH conditions As(V) is primarily present as an anion (i.e., H2AsO4-) while As(III) tends to be uncharged (i.e., H3AsO3), making it much more difficult to remove through the existing treatment techniques such as adsorption and reverse osmosis (RO). Although many studies exist establishing arsenic concentrations across Wisconsin, there is a lack of investigations into the concentrations of each …

Assessing Beaver Dam Dynamics In The Logan-Little Bear Watershed, Connor Penrod

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

This paper seeks to address a knowledge gap concerning how flood events impact beaver dams over time. To address this gap, I took four time-snapshots of beaver dams, mapping them across the Utah portion of the Logan-Little Bear watershed, from 2009 to 2016 to bookend a large flood event in 2011. I assessed dam status (intact, breached, or blown out) for each dam mapped to assess the impact of the large spring runoff on the dam status. Assessing dam status over time allowed me to assess the change in condition over time, from before to several years after, while also …

Extreme Dynamics Of Nanomaterials Under High-Rate Mechanical Stimuli, Wanting Xie

Doctoral Dissertations

Nanomaterials demonstrate novel mechanical properties attributed to the extremely large interfacial area. At quasi-static rates, the interfacial interactions are crucial in mechanical behaviors, however, materials under extreme mechanical stimuli are rarely studied at nanoscale. With an advanced laser-induced projectile impact test, we perform supersonic impact of micro-projectiles on polymer films, multilayer graphene, carbon- based nanocomposites membranes as well as individual micro-fibers, to study the interface interactions in the high-rate regime, and develop a simplified model to characterize the ballistic performance of materials.

Comparing Proton Momentum Distributions In A = 2 And 3 Nuclei Via 2H 3H And 3He (E,E′P) Measurements, R. Cruz-Torres, F. Hauenstein, A. Schmidt, D. Nguyen, D. Abrams, H. Albataineh, S. Alsalmi, D. Androic, K. Aniol, W. Armstrong, J. Arrington, H. Atac, D. Bulumulla, C. E. Hyde, V. Khachatryan, M. N.H. Rashad, L. B. Weinstein, Z. Y. Ye, J. Zhang, Jefferson Lab Hall A Tritium Collaboration

Physics Faculty Publications

We report the first measurement of the (e, e' p) reaction cross-section ratios for Helium-3 (³He), Tritium (³H), and Deuterium (d). The measurement covered a missing momentum range of 40 ≤ p_miss ≤ 550 MeV/c, at large momentum transfer ({Q²} ≈ 1.9 (GeV/c)²) and x_B > 1, which minimized contributions from non quasi-elastic (QE) reaction mechanisms. The data is compared with planewave impulse approximation (PWIA) calculations using realistic spectral functions and momentum distributions. The measured and PWIA-calculated cross-section ratios for ³He/d and ³H/d extend to just above the typical …

Muon Capture In Nuclei: An Ab Initio Approach Based On Green's Function Monte Carlo Methods, A. Lovato, N. Rocco, Rocco Schiavilla

Physics Faculty Publications

An ab initio Green’s function Monte Carlo (GFMC) method is introduced for calculating total rates of muon weak capture in light nuclei with mass number A ≤ 12. As a first application of the method, we perform a calculation of the rate in ³H and ⁴He in a dynamical framework based on realistic two- and three-nucleon interactions and realistic nuclear charge-changing weak currents. The currents include one- and two-body terms induced by π-and ρ-meson exchange, and N-to-Δ excitation, and are constrained to reproduce the empirical value of the Gamow-Teller matrix element in tritium. We investigate the sensitivity of …

Distributary Channel Networks As Moving Boundaries: Causes And Morphodynamic Effects, Robert C. Mahon, John B. Shaw, Wun-Tao Ke, Christopher A. Cathcart

Earth and Environmental Sciences Faculty Publications

We propose an exploratory model to describe the morphodynamics of distributary channel network growth on river deltas. The interface between deep channels and the shallow, unchannelized delta front deposits is modeled as a moving boundary. Steady flow over the unchannelized delta front is friction dominated and modeled by Laplace's equation. Shear stress along the network boundary produces nonlinear erosion rates at the interface, causing the boundary to move and network elements (channels and branches) to form. The model was run for boundary conditions resembling the Wax Lake Delta in coastal Louisiana, 20 parameterizations of sediment transport, and 3 …

The Effects Of Finite Precision On The Simulation Of The Double Pendulum, Rebecca Wild

Senior Honors Projects, 2010-2019

We use mathematics to study physical problems because abstracting the information allows us to better analyze what could happen given any range and combination of parameters. The problem is that for complicated systems mathematical analysis becomes extremely cumbersome. The only effective and reasonable way to study the behavior of such systems is to simulate the event on a computer. However, the fact that the set of floating-point numbers is finite and the fact that they are unevenly distributed over the real number line raises a number of concerns when trying to simulate systems with chaotic behavior. In this research we …

Virtual Scene Simulation Of Pilot Response In Taking-Off And Landing Processes Of Carrier-Based Aircraft, Ke Peng, Chenglin Xu, Songyang Liu, Minggao Li, Zhao Xin

Journal of System Simulation

Abstract: A research and implementation method based on biomechanics simulation and virtual scene simulation was put forward to investigate the dynamics responses of pilots during the taking off and landing processes of carrier-based aircraft. The human biomechanics calculation of pilots and 3D virtual scene simulation of flight scene were combined to design and develop the integrated virtual simulation platform. This platform has the functions of data management and analysis, human biological dynamics calculation, synchronous analysis of key results, 3D virtual scene simulation of taking-off and landing processes and human response. The verification was carried out using the experiments from …

Water Entry Of Spheres At Various Contact Angles, Nathan B. Spiers, Mohammad M. Mansoor, Jesse Belden, Tadd T. Truscott

Mechanical and Aerospace Engineering Faculty Publications

It is well known that the water entry of a sphere causes cavity formation above a critical impact velocity as a function of the solid-liquid contact angle (Duez et al. 2007). Using a rough sphere with a contact angle of 120^◦, Aristoff & Bush (2009) showed that there are four different cavity shapes dependent on the Bond and Weber numbers (i.e., quasi-static, shallow, deep and surface). We experimentally alter the Bond number, Weber number and contact angle of smooth spheres and find two key additions to the literature: 1) Cavity shape also depends on the contact angle; 2) …

Sponges Structure Water-Column Characteristics In Shallow Tropical Coastal Ecosystems, Marla M. Valentine, Mark J. Butler Iv

Biological Sciences Faculty Publications

Sponges can have powerful effects on ecosystem processes in shallow tropical marine ecosystems. They drive benthic-pelagic coupling by filtering dissolved and particulate organic matter from the water column, alter water chemistry in association with their symbiotic microorganisms, and increase habitat structural complexity. Anthropogenic degradation of coastal waters is widespread and can reduce the density and diversity of foundation species such as sponges, potentially diminishing their contributions to ecosystem processes. We used a novel mesocosm design that minimized artifacts associated with traditional single-species and closed-system filtration experiments to examine the effects of water turnover and sponge biomass on water-column properties. Using …

Nonadiabatic Dynamics: A Semiclassical Approach, Ruixi Wang

Wayne State University Dissertations

Nonadiabatic dynamics has been an essential part of quantum chemistry since the 1930’s. Nonadiabatic effects play a crucial role in photo-physical and photo-chemical reactions for both small and large molecules in both gas and condensed phases. Modeling dynamics of photoinduced reactions has been a new frontier of chemistry. Many dynamical phenomena, such as intersystem crossing, non-radiative relaxation, and charge energy transfer, require a nonadiabatic description which incorporates transitions between electronic states.

In Chapter 2, the property of scattering region in the semiclassical limit is investigated. We suggest that a nuclear wavepacket close enough to the conical intersection will propagate ballistically …

Geometric And Dynamical Properties Of The Infinite Dihedral Group, Bryan Goldberg

Legacy Theses & Dissertations (2009 - 2024)

For a tuple $A= (A_1, A_2, \ldots , A_n)$ of elements in a unital Banach algebra $\mathcal{B}$ its \textit{projective (joint) spectrum} $P(A)$ is the collection of $z~\in~\mathbb{C}^n$ such that $A(z)~=~z_1 A_1 + z_2 A_2 + \ldots + z_n A_n$ is not invertible. We call the complement of $P(A)$ the projective resolvent set, $P^c(A) = \C^n \setminus P(A)$. In this dissertation the primary focus will be on the infinite dihedral group $D_\infty = \langle a,t\mid a^2=t^2 =1 \rangle$ and the left regular representation $\lambda$ acting on $l^2(D_\infty)$ giving the tuple $ \big(I, \lb(a),\lb(t)\big)$. First, using the fundamental form $\Omega_A~=~- \omega _A …

Instability Of Flux Flow And Production Of Vortex-Antivortex Pairs By Current-Driven Josephson Vortices In Layered Superconductors, Ahmad Sheikhzada, Alex Gurevich

Physics Faculty Publications

We report numerical simulations of the nonlinear dynamics of Josephson vortices driven by strong dc currents in layered superconductors. Dynamic equations for interlayer phase differences in a stack of coupled superconducting layers were solved to calculate a drag coefficient η(J) of the vortex as a function of the perpendicular dc current density J. It is shown that Cherenkov radiation produced by a moving vortex causes significant radiation drag increasing η(v) at high vortex velocities v and striking instabilities of driven Josephson vortices moving faster than a terminal v_c. The steady-state flux flow breaks down at ν > v …