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Publications

Engineering

2016

Articles 1 - 6 of 6

Full-Text Articles in Physical Sciences and Mathematics

Wave Motion Induced By Turbulent Shear Flows Over Growing Stokes Waves, Shahrdad Sajjadi, Serena Robertson, Rebecca Harvey, Mary Brown Dec 2016

Wave Motion Induced By Turbulent Shear Flows Over Growing Stokes Waves, Shahrdad Sajjadi, Serena Robertson, Rebecca Harvey, Mary Brown

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The recent analytical of multi-layer analyses proposed by Sajjadi et al. (J Eng Math 84:73, 2014) (SHD14 therein) is solved numerically for atmospheric turbulent shear flows blowing over growing (or unsteady) Stokes (bimodal) water waves, of low-to-moderate steepness. For unsteady surface waves, the amplitude a(t)∝ekcita(t)∝ekcit, where kcikci is the wave growth factor, k is the wavenumber, and cici is the complex part of the wave phase speed, and thus, the waves begin to grow as more energy is transferred to them by the wind. This will then display the critical height to a point, where the thickness of the inner …

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On Safety Assessment Of Novel Approach To Robust Uav Flight Control In Gusty Environments, Vladimir Golubev, Petr Kazarin, William Mackunis, Sherry Borener, Derek Hufty Sep 2016

On Safety Assessment Of Novel Approach To Robust Uav Flight Control In Gusty Environments, Vladimir Golubev, Petr Kazarin, William Mackunis, Sherry Borener, Derek Hufty

Publications

In a follow-up to our previous study, the current work examines the gust-induced “cone of uncertainty” in a small unmanned aerial vehicle’s (UAV) flight trajectory addressed in the context of safety assessments of UAV operations. Such analysis is a critical facet of the integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), particularly in terminal airspace. The paper describes a predictive, robust feedback-loop flight control model that is applicable to various classes of UAVs and unsteady flight-path scenarios. The control design presented in this paper extends previous research results by demonstrating asymptotic (zero steady-state error) altitude regulation …

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Aviation And Cybersecurity: Opportunities For Applied Research, Jon Haass, Radhakrishna Sampigethaya, Vincent Capezzuto Jul 2016

Aviation And Cybersecurity: Opportunities For Applied Research, Jon Haass, Radhakrishna Sampigethaya, Vincent Capezzuto

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Aviation connects the global community and is moving more people and payloads faster than ever. The next decade will experience an increase in manned and unmanned aircraft and systems with new features and unprecedented applications. Cybertechnologies—including software, computer networks, and information technology—are critical and fundamental to these advances in meeting the needs of the aviation ecosystem of aircraft, pilots, personnel, passengers, stakeholders, and society. This article discusses current and evolving threats as well as opportunities for applied research to improve the global cybersecurity stance in the aviation and connected transportation industry of tomorrow.

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Thermoelastic Waves In Microstructured Solids, Arkadi Berezovski, Mihhail Berezovski Feb 2016

Thermoelastic Waves In Microstructured Solids, Arkadi Berezovski, Mihhail Berezovski

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Thermoelastic wave propagation suggests a coupling between elastic deformation and heat conduction in a body. Microstructure of the body influences the both processes. Since energy is conserved in elastic deformation and heat conduction is always dissipative, the generalization of classical elasticity theory and classical heat conduction is performed differently. It is shown in the paper that a hyperbolic evolution equation for microtemperature can be obtained in the framework of the dual internal variables approach keeping the parabolic equation for the macrotemperature. The microtemperature is considered as a macrotemperature fluctuation. Numerical simulations demonstrate the formation and propagation of thermoelastic waves in …

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Signal Flow Graph Approach To Efficient Dst I-Iv Algorithms, Sirani M. Perera Jan 2016

Signal Flow Graph Approach To Efficient Dst I-Iv Algorithms, Sirani M. Perera

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In this paper, fast and efficient discrete sine transformation (DST) algorithms are presented based on the factorization of sparse, scaled orthogonal, rotation, rotation-reflection, and butterfly matrices. These algorithms are completely recursive and solely based on DST I-IV. The presented algorithms have low arithmetic cost compared to the known fast DST algorithms. Furthermore, the language of signal flow graph representation of digital structures is used to describe these efficient and recursive DST algorithms having (n�1) points signal flow graph for DST-I and n points signal flow graphs for DST II-IV.

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Plasma Density Analysis Of Cubesat Wakes In The Earth’S Ionosphere, Robert M. Albarran Ii, Aroh Barjatya Jan 2016

Plasma Density Analysis Of Cubesat Wakes In The Earth’S Ionosphere, Robert M. Albarran Ii, Aroh Barjatya

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Spinning or tumbling CubeSats with Langmuir probes deployed on booms will render spin-modulated plasma densities as the probes move in and out of the spacecraft wake. It is traditionally assumed that the lower-density measurements from the spin cycle are made in the spacecraft wake, and the higher-density measurements are outside the wake. Although this assumption is valid for larger spacecraft in the Earth’s ionosphere, this paper scrutinizes its validity for CubeSats in similar conditions. Spacecraft–plasma interactions (surface charging, plasma sheaths, and wakes) are less understood for CubeSats, and the small CubeSat dimensions must be considered with respect to characteristic length …

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