Physical Sciences and Mathematics Commons^™

Reduced-Order Dynamic Modeling And Robust Nonlinear Control Of Fluid Flow Velocity Fields, Anu Kossery Jayaprakash, William Mackunis, Vladimir Golubev, Oksana Stalnov

Publications

A robust nonlinear control method is developed for fluid flow velocity tracking, which formally addresses the inherent challenges in practical implementation of closed-loop active flow control systems. A key challenge being addressed here is flow control design to compensate for model parameter variations that can arise from actuator perturbations. The control design is based on a detailed reduced-order model of the actuated flow dynamics, which is rigorously derived to incorporate the inherent time-varying uncertainty in the both the model parameters and the actuator dynamics. To the best of the authors’ knowledge, this is the first robust nonlinear closed-loop active flow …

An Extension Of Asgeirsson's Mean Value Theorem For Solutions Of The Ultra-Hyperbolic Equation In Dimension Four, Guillem Cobos, Brendan Guilfoyle

Publications

In 1937 Asgeirsson established a mean value property for solutions of the general ultra-hyperbolic equation in 2n variables. In the case of four variables, it states that the integrals of a solution over certain pairs of conjugate circles are the same. In this paper we extend this result to non-degenerate conjugate conics, which include the original case of conjugate circles and adds the new case of conjugate hyperbolae. The broader context of this result is the geometrization of Fritz John’s 1938 analysis of the ultra-hyperbolic equation. Solutions of the equation arise as the compatibility for functions on line space to …

Statistical Spectral Characteristics Of Three-Dimensional Winds In The Mesopause Region Revealed By The Andes Lidar, Qian Li, Alan Z. Liu, Shao Dong Zhang, Chun Ming Huang, Kai Ming Huang, Yun Gong, Quan Gan, Yan Ying Yan, Hang Liu

Publications

By analyzing data recorded at the Andes Lidar Observatory in Cerro Pachon, Chile (30.3°S, 70.7°W) from May 2014 to July 2019, we investigated the fundamental features of three-dimensional wind and temperature spectra. The vertical wavenumber spectral amplitudes of horizontal winds show obvious seasonal variations that are closely related to the seasonal variations in the source and background winds. The wavenumber spectral slopes of the horizontal winds are systematically less negative than −3, with mean values of −1.96 and −2.18 for zonal and meridional winds, respectively. The zonal and meridional wind frequency spectra have mean slopes of −1.37 and −1.56, respectively; …

Mosaic: A Satellite Constellation To Enable Groundbreaking Mars Climate System Science And Prepare For Human Exploration, Robert J. Lillis, Aroh Barjatya, David Mitchell, Luca Montabone, Nicholas Heavens, Tanya Harrison, Cassie Stuurman, Scott Guzewich, Scott England, Paul Withers, Mike Chaffin, Shannon Curry, Chi Ao, Steven Matousek, Nathan Barba, Ryan Woodley, Isaac Smith, Gordon R. Osinski, Armin Kleinböhl, Leslie Tamppari, Michael Mischna, David Kass, Michael Smith, Michael Wolff, Melinda Kahre, Aymeric Spiga, François Forget, Bruce Cantor, Justin Deighan, Amanda Brecht, Stephen Bougher, Christopher M. Fowler, David Andrews, Martin Patzold, Kerstin Peter, Silvia Tellmann, Mark Lester, Beatriz Sánchez-Cano, Janet Luhmann, François Leblanc, Jasper Halekas, David Brain, Xiaohua Fang, Jared Espley, Hermann Opgenoorth, Oleg Vaisberg, David Hinson, Sami Asmar, Joshua Vander Hook, Ozgur Karatekin, Abhishek Tripathi

Publications

The Martian climate system has been revealed to rival the complexity of Earth's. Over the last 20 yr, a fragmented and incomplete picture has emerged of its structure and variability; we remain largely ignorant of many of the physical processes driving matter and energy flow between and within Mars' diverse climate domains. Mars Orbiters for Surface, Atmosphere, and Ionosphere Connections (MOSAIC) is a constellation of ten platforms focused on understanding these climate connections, with orbits and instruments tailored to observe the Martian climate system from three complementary perspectives. First, low-circular near-polar Sun-synchronous orbits (a large mothership and three smallsats spaced …

A Quasi-27-Day Oscillation Activity From The Troposphere To The Mesosphere And Lower Thermosphere At Low Latitudes, Hao Cheng, Alan Z. Liu, Kaiming Huang, Shaodong Zhang, Chunming Huang, Yun Gong

Publications

Using meteor radar, radiosonde observations and MERRA-2 reanalysis data from 12 August to 31 October 2006, we report a dynamical coupling from the tropical lower atmosphere to the mesosphere and lower thermosphere through a quasi-27-day intraseasonal oscillation (ISO). It is interesting that the quasi-27-day ISO is observed in the troposphere, stratopause and mesopause regions, exhibiting a three-layer structure. In the MLT, the amplitude in the zonal wind increases from about 4 ms−1 at 90 km to 15 ms−1 at 100 km, which is diferent from previous observations that ISOs occurs generally in winter with an amplitude peak at about 80–90 …

Evolving To Non-Round Weingarten Spheres: Integer Linear Hopf Flows, Brendan Guilfoyle, Wilhelm Klingenberg

Publications

In the 1950’s Hopf gave examples of non-round convex 2-spheres in Euclidean 3-space with rotational symmetry that satisfy a linear relationship between their principal curvatures. In this paper, we investigate conditions under which evolving a smooth convex rotationally symmetric sphere by a linear combination of its radii of curvature yields a Hopf sphere. When the coefficients of the flow have certain integer values, the fate of an initial sphere is entirely determined by the local geometry of its isolated umbilic points. A variety of behaviours is uncovered: convergence to round spheres and non-round Hopf spheres, as well as divergence to …

Atmospheric Tomography Using The Nordic Meteor Radar Cluster And Chilean Observation Network De Meteor Radars: Network Details And 3d-Var Retrieval, Gunter Stober, Alan Z. Liu, Zishun Qiao, Alexander Kozlovsky, Masaki Tsutsumi, Chris Hall, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Patrick J. Espy, Robert E. Hibbins, Nicholas Mitchell

Publications

Ground-based remote sensing of atmospheric parameters is often limited to single station observations by vertical profiles at a certain geographic location. This is a limiting factor for investigating gravity wave dynamics as the spatial information is often missing, e.g., horizontal wavelength, propagation direction or intrinsic frequency. In this study, we present a new retrieval algorithm for multistatic meteor radar networks to obtain tomographic 3-D wind fields within a pre-defined domain area. The algorithm is part of the Agile Software for Gravity wAve Regional Dynamics (ASGARD) and called 3D-Var, and based on the optimal estimation technique and Bayesian statistics. The performance …

Aessa Young Professionals Forum Webinar “Technologies And Skills That Will Gearup The Aerospace Industry Post Pandemic” - A Global Perspective With An Emphasis On South Africa October 2021, Linda Vee Weiland

Publications

A webinar presentation for AeSSA Young Professionals.

Options And Experiences For Online Chemistry Laboratory Instruction, Emily Faulconer, Matt Morgan

Publications

While online course offerings have been on the rise for many years, there was a rapid transition to online courses due to campus closures and social distancing protocols associated with the COVID-19 pandemic. This has caused significant disruption in traditional chemistry laboratory activities. In this chapter, features of various distance laboratory approaches options are presented, including wet chemistry and dry laboratory options. Because the existing research comparing effectiveness of these strategies is scarce, no attempt is made to argue the effectiveness of one modality over the other, but rather advantages and disadvantages of each method are presented and discussed. The …

Observations And Validation Of Plasma Density, Temperature, And O+ Abundance From A Langmuir Probe Onboard The International Space Station, Shantanab Debchoudhury, Aroh Barjatya, Joseph I. Minow, Victoria N. Coffey, Michael O. Chandler

Publications

The Floating Potential Measurement Unit (FPMU) has been operational on board the International Space Station (ISS) since 2006. One of the instruments in the FPMU suite is a spherical wide-sweeping Langmuir probe, referred to as the WLP, which is sampled at a temporal cadence of 1 s giving in-situ measurements of the plasma density and electron temperature. In this study we present our refinements to the Langmuir probe analysis algorithm that address the uncertainties associated with photoelectron emission current from the metal probe. We also derive the fraction of O⁺ ions as a secondary data product, which shows decrease …

Venus Mountain Waves In The Upper Atmosphere Simulated By A Time-Invariant Linear Full-Wave Spectral Model, Michael P. Hickey, Thomas Navarro, Gerald Schubert, Richard L. Walterscheid

Publications

A 2-D spectral full-wave model is described that simulates the generation and propagation of mountain waves over idealized topography in Venus’ atmosphere. Modeled temperature perturbations are compared with the Akatsuki observations. Lower atmosphere eddy diffusivity and stability play a major role in the upward propagation of gravity waves from their mountain sources. Two local times (LT) are considered. For LT = 11h the waves are blocked by a critical level near 100 km altitude, while for LT = 16 h the waves propagate into the thermosphere. As a result of the small scale height in the Venus thermosphere, for LT …

Splash: Learnable Activation Functions For Improving Accuracy And Adversarial Robustness, Mohammadamin Tavakoli, Forest Agostinelli, Pierre Baldi

Publications

We introduce SPLASH units, a class of learnable activation functions shown to simultaneously improve the accuracy of deep neural networks while also improving their robustness to adversarial attacks. SPLASH units have both a simple parameterization and maintain the ability to approximate a wide range of non-linear functions. SPLASH units are: (1) continuous; (2) grounded (f(0)=0"); (3) use symmetric hinges; and (4) their hinges are placed at fixed locations which are derived from the data (i.e. no learning required). Compared to nine other learned and fixed activation functions, including ReLU and its variants, SPLASH units show superior performance across three datasets …

Nonlinear Schrödinger Equation Solitons On Quantum Droplets, A. Ludu, A.S. Carstea

Publications

Irrotational flow of a spherical thin liquid layer surrounding a rigid core is described using the defocusing nonlinear Schrödinger equation. Accordingly, azimuthal moving nonlinear waves are modeled by periodic dark solitons expressed by elliptic functions. In the quantum regime the algebraic Bethe ansatz is used in order to capture the energy levels of such motions, which we expect to be relevant for the dynamics of the nuclear clusters in deformed heavy nuclei surface modeled by quantum liquid drops. In order to validate the model we match our theoretical energy spectra with experimental results on energy, angular momentum, and parity for …

Corrigendum: The Remote Observatories Of The Southeastern Association For Research In Astronomy (Sara), William C. Keel, Terry Oswalt, Peter Mack, Gary Henson, Todd Hillwig, Daniel Batcheldor, Robert Berrington, Chris De Pree, Dieter Hartmann, Martha Leake, Javier Licandro, Brian Murphy, James Webb, Matt A. Wood

Publications

Bill Gray of Project Pluto brought to our attention an error of 0.03° in the listed latitude of our Kitt Peak telescope. While correcting the table where this occurred, we also take the opportunity to update the instrument properties and weather statistics of our remote telescopes

Collisions In A Gas-Rich White Dwarf Planetary Debris Disc, Ted Von Hippel, University College London, Scott J. Kenyon, Jay Farihi, Erik Dennihy, Boris T. Gänsicke, J.J. Hermes, Carl Melis

Publications

WD 0145+234 is a white dwarf that is accreting metals from a circumstellar disc of planetary material. It has exhibited a substantial and sustained increase in 3–5 μm flux since 2018. Follow-up Spitzer photometry reveals that emission from the disc had begun to decrease by late 2019. Stochastic brightening events superimposed on the decline in brightness suggest the liberation of dust during collisional evolution of the circumstellar solids. A simple model is used to show that the observations are indeed consistent with ongoing collisions. Rare emission lines from circumstellar gas have been detected at this system, supporting the emerging picture …

Auroral Heating Of Plasma Patches Due To High-Latitude Reconnection, Joaquin Diaz Pena, Joshua Semeter, Yukitoshi Nishimura, Roger Varney, Ashton Reimer, Marc Hairston, Matthew Zettergren, Michael Hirsch, Olga Verkhoglyadova, Keisuke Hosokawa, Kazuo Shiokawa

Publications

This study exploits the volumetric sampling capabilities of the Resolute Bay Incoherent Scatter Radar (RISR-N) in collaboration with all-sky imagery and in-situ measurements (DMSP) to examine the interplay between cold plasma transport and auroral precipitation during a high-latitude lobe reconnection event on the dawn side. The IMF had an impulsive negative excursion in B$_z$ embedded within a prolonged period of B$_z>0$ and B$_y

The Economic Value Of America’S Estuaries: 2021 Report, Tracy Rouleau, Charles S. Colgan, Jefferey Adkins, Castelletto Anthony, Dirlam Patty, Shannon Lyons, Hilary Stevens

Publications

This study builds on the work completed in 2009, “The Economic and Market Value of Coasts and Estuaries: What’s At Stake?,” a report by NOAA in collaboration with the Center for the Blue Economy and the Ocean Foundation, at the request of Restore America’s Estuaries. Like the 2009 study, the 2021 update uses the same data sources (Census, Bureau of Labor Statistics, Bureau of Economic Analysis and NOAA), and looks in detail at the same five major sectors of the U.S. economy (fisheries, energy infrastructure, marine transportation, real estate, and recreation) from 2009-2018.

The 2021 update includes the economic …

Inferring The Evolution Of A Large Earthquake From Its Acoustic Impacts On The Ionosphere, P. A. Inchin, J. B. Snively, M. D. Zettergren, Y. Kaneko, A. Komjathy

Publications

We investigate the possibility to constrain the evolution of the 2016 M7.8 Kaikoura earthquake evolution based on Global Positioning System signal-derived ionospheric total electron content (TEC) perturbations, that represent plasma responses to infrasonic acoustic waves (IAWs) generated by surface motion. This earthquake exhibited unusual complexity and some first-order aspects of its evolution remain unclear; for example, how and when the Papatea fault (PF) and the corresponding large surface deformation occurred. For various earthquake models, a seismic wave propagation code is used to simulate time-dependent surface deformations, which then excite IAWs in a 3D compressible nonlinear atmospheric model, coupled with a …

Atmospheric Tomography Using The Nordic Meteor Radar Cluster And Chilean Observation Network De Meteor Radars: Network Details And 3dvar Retrieval, Gunter Stober, Alan Liu, Zishun Qiao, Alexander Kozlovsky, Masaki Tsutsumi, Chris Hall, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Patrick J. Espy, Robert E. Hibbins, Nicholas Mitchell

Publications

Ground-based remote sensing of atmospheric parameters is often limited to single station observations of vertical profiles at a certain geographic location. This can be a limiting factor to investigating gravity wave dynamics. In this study we present a new retrieval algorithm for multi-static meteor radar networks to obtain tomographic 3D wind fields within a pre-defined domain area. The algorithm is part of the Agile Software for Gravity wAve Regional Dynamics (ASGARD) called 5 3DVAR, and based on the optimal estimation technique and Bayesian statistics. The performance of the 3DVAR retrieval is demonstrated using two meteor radar networks, the Nordic Meteor …

Ieee Access Special Section Editorial: Software-Defined Networks For Energy Internet And Smart Grid Communication, Mubashir Husain Rehmani, Alan Davy, Brendan Jennings, Zeeshan Kaleem, Akhilesh S. Thyagaturu, Hassnaa Moustafa, Al-Sakib Khan Pathan

Publications

A new network paradigm of software-defined networks (SDNs) is being widely adapted to efficiently monitor and manage the communication networks with a global perspective. SDN has a key networking feature that separates control and data plane. Today, due to its inherent benefits, SDN has been widely applied to various networking domains, including data centers, 5G Access and Core network functions, wide area network (WAN), enterprise, optical networks, underwater sensor networks (UWSNs), energy Internet (EI), and smart grid (SG).

Cross Domain Iw Threats To Sof Maritime Missions: Implications For U.S. Sof, Gary C. Kessler, Diane M. Zorri

Publications

As cyber vulnerabilities proliferate with the expansion of connected devices, wherein security is often forsaken for ease of use, Special Operations Forces (SOF) cannot escape the obvious, massive risk that they are assuming by incorporating emerging technologies into their toolkits. This is especially true in the maritime sector where SOF operates nearshore in littoral zones. As SOF—in support to the U.S. Navy— increasingly operate in these contested maritime environments, they will gradually encounter more hostile actors looking to exploit digital vulnerabilities. As such, this monograph comes at a perfect time as the world becomes more interconnected but also more vulnerable.

Control Over Skies: Survivability, Coverage, And Mobility Laws For Hierarchical Aerial Base Stations, Vishal Sharma, Navuday Sharma, Mubashir Husain Rehmani, Haris Pervaiz

Publications

Aerial Base Stations (ABSs) have gained significant importance in the next generation of wireless networks for accommodating mobile ground users and flash crowds with high convenience and quality. However, to achieve an efficient ABS network, many factors pertaining to ABS flight, governing laws and information transmissions must be studied. In this article, multi-drone communications are studied in three major aspects, survivability, coverage, and mobility laws, which optimize the multitier ABS network to avoid issues related to inter-cell interference, deficient energy, frequent handovers, and lifetime. The article includes simulation results of hierarchical ABS allocations for handling a set of users over …

Cyber Supply Chain Risk Management: Implications For The Sof Future Operating Environment, J. Philip Craiger, Laurie Lindamood-Craiger, Diane M. Zorri

Publications

The emerging Cyber Supply Chain Risk Management (C-SCRM) concept assists at all levels of the supply chain in managing and mitigating risks, and the authors define C-SCRM as the process of identifying, assessing, and mitigating the risks associated with the distributed and interconnected nature of information and operational technology products and service supply chains. As Special Operations Forces increasingly rely on sophisticated hardware and software products, this quick, well-researched monograph provides a detailed accounting of C-SCRM associated laws, regulations, instructions, tools, and strategies meant to mitigate vulnerabilities and risks—and how we might best manage the evolving and ever-changing array of …

Cyber Security Framework For Vehicular Network Based On A Hierarchical Game, Hichem Sedjelmaci, Imane Horiya Brahmi, Nirwan Ansari, Mubashir Husain Rehmani

Publications

The growth of electronic devices in connected vehicles and their connections to the untrusted network, present unprecedented exposure to attacks. Therefore, a reliable and efficient cyber security framework is mandatory to protect vehicular networks against the cyber attackers. Thereby, we propose a cyber defense framework based on a hierarchical cooperative game to secure legitimate vehicles from attacks. In the proposed hierarchical game, there are two kinds of players, the head agent and secondary agents that cooperate between each other to detect, predict and react efficiently against suspected attacks. The Intrusion Detection System (IDS), Intrusion Prediction System (IPS), and Intrusion Reaction …

Investigating The Impacts Of Crash Prediction Models On Quantifying Safety Effectiveness Of Adaptive Signal Control Systems, Weimin Jin, Mashrur Chowdhury, Sakib Mahmud Khan, Patrick Gerard

Publications

Introduction: Adaptive Signal Control System (ASCS) can improve both operational and safety benefits at signalized corridors. Methods: This paper develops a series of models accounting for model forms and possible predictors and implements these models in Empirical Bayes (EB) and Fully Bayesian (FB) frameworks for ASCS safety evaluation studies. Different models are validated in terms of the ability to reduce the potential bias and variance of prediction and improve the safety effectiveness estimation accuracy using real-world crash data from non-ASCS sites. This paper then develops the safety effectiveness of ASCS at six different corridors with a total of 65 signalized …

Parking Recommender System Privacy Preservation Through Anonymization And Differential Privacy, Yasir Saleem Shaikh, Mubashir Husain Rehmani, Noel Crespi, Roberto Minerva

Publications

Recent advancements in the Internet of Things (IoT) have enabled the development of smart parking systems that use services of third-party parking recommender system to provide recommendations of personalized parking spot to users based on their past experience. However, the indiscriminate sharing of users’ data with an untrusted (or semitrusted) parking recommender system may breach the privacy because users’ behavior and mobility patterns could be inferred by analyzing their past history. Therefore, in this article, we present two solutions that preserve privacy of users in parking recommender systems while analyzing the past parking history using k-anonymity (anonymization) and differential privacy …

Reduced Multiplicative Complexity Discrete Cosine Transform (Dct) Circuitry, Sirani Kanchana Mututhanthrige Perera

Publications

System and techniques for reduced multiplicative complex­ity discrete cosine transform (DCT) circuitry are described herein. An input data set can be received and, upon the input data set, a self-recursive DCT technique can be performed to produce a transformed data set. Here, the self-recursive DCT technique is based on a product of factors of a specified type of DCT technique. Recursive components of the technique are of the same DCT type as that of the DCT technique. The transformed data set can then be produced to a data con­sumer.

Knowledge Network Embedding Of Transcriptomic Data From Spaceflown Mice Uncovers Signs And Symptoms Associated With Terrestrial Diseases, Amber M. Paul, Charlotte A. Nelson, Ana Uriarte Acuna, Ryan T. Scott, Atul J. Butte, Egle Cekanaviciute, Sergio E. Baranzini

Publications

There has long been an interest in understanding how the hazards from spaceflight may trigger or exacerbate human diseases. With the goal of advancing our knowledge on physiological changes during space travel, NASA GeneLab provides an open-source repository of multi-omics data from real and simulated spaceflight studies. Alone, this data enables identification of biological changes during spaceflight, but cannot infer how that may impact an astronaut at the phenotypic level. To bridge this gap, Scalable Precision Medicine Oriented Knowledge Engine (SPOKE), a heterogeneous knowledge graph connecting biological and clinical data from over 30 databases, was used in combination with GeneLab …

Towards Equity In Energy Efficiency Analyses, John Wamburu, Emma Grazier, David Irwin, Christine Crago, Prashant Shenoy

Publications

The electric grid has begun a profound transition from primarily using carbon-intensive energy to instead using carbon-free renewable energy. In parallel, smart meters and other sensors are now providing us unparalleled visibility into the energy-efficiency of building and grid operations. Researchers are actively using building and grid energy data from these sensors to develop analytics techniques, e.g., using machine learning, that can improve energy-efficiency and facilitate the energy transition. Unfortunately, much of this research ignores the impact of these analytics on equity. That is, while current data analytics techniques may accurately identify energy-inefficiencies, they generally do not contextualize the underlying …

Cyber Insurance Effects On Cyber Hygiene: Does The Homeostatic Effect Apply?, Wendi M. Kappers, Aaron Glassman, Michael S. Wills

Publications

A theoretical framework and research strategy is proposed to gain insight into perceptions and decisions as to how SMBs make decisions regarding cybersecurity hygiene measures, which could lead to betterinformed decisions regarding insurance as part of an ISA program, as well as have a bearing on policy structures and pricing for such insurance. This is because the definition of “cybersecurity hygiene habits”(CHH) as a task appears to vary within the industry and makes the practice hard to measure and evaluate. Research suggests that there may be a poorly understood connection between CHHs undertaken by organizations and their perceptions and/or adoption …