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1. ISS and integral-ISS of switched systems with nonlinear supply functions

   https://doi.org/10.1007/s00498-021-00306-x  

   Liu, Shenyu ; Tanwani, Aneel ; Liberzon, Daniel ( October 2021 , Mathematics of Control, Signals, and Systems)

   The problem of input-to-state stability (ISS) and its integral version (iISS) are considered for switched nonlinear systems with inputs, resets and possibly unstable subsystems. For the dissipation inequalities associated with the Lyapunov function of each subsystem, it is assumed that the supply functions, which characterize the decay rate and ISS/iISS gains of the subsystems, are nonlinear. The change in the value of Lyapunov functions at switching instants is described by a sum of growth and gain functions, which are also nonlinear. Using the notion of average dwell-time (ADT) to limit the number of switching instants on an interval, and the notion of average activation time (AAT) to limit the activation time for unstable systems, a formula relating ADT and AAT is derived to guarantee ISS/iISS of the switched system. Case studies of switched systems with saturating dynamics and switched bilinear systems are included for illustration of the results.

    

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2. Numerical Modeling of the Plasmakristall-4 Experiment on the ISS

   https://doi.org/10.2514/6.2023-1587  

   Vermillion, Katrina ; Terrell, Abbie ; Gehr, Emerson ; Kostadinova, Evdokiya G. ; Hartmann, Peter ; Matthews, Lorin S. ; Hyde, Truell W. ( January 2023 , American Institute of Aeronautics and Astronautics)

   The microgravity environment of the Plasmakristall-4 experiment on the International Space Station provides a laboratory for exploring plasma-mediated interactions among charged dust grains in fully three-dimensional space. Away from the strong influence of Earth's gravity, the dust grains can levitate in the bulk of the plasma, where they have been observed to form extended filamentary structures aligned with the discharge tube axis. These structures can be used as a macroscopic analogue for other self-organizing systems, including electrorheological fluids and liquid crystals, and the success of the analogy depends on a thorough understanding of the mechanisms guiding the dust interaction potential. Here we present the results from molecular dynamics simulations of the ion flow past isolated dust chains within the dust cloud and the dust cloud macrostructure. Although dust grains are known to respond on the millisecond timescale, analysis reveals that periodic variations of plasma conditions on the microsecond timescale significantly affect dust structure formation. In addition to the expected formation of filamentary dust chains in the dust cloud macrostructure, dust grains in a large cloud are also observed to organize into ordered positions on the surface of nested cylinders, in agreement with experimental observations. 

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3. ISS inequalities for vector versions of Halanay’s inequality and of the trajectory-based approach

   https://doi.org/10.1016/j.ejcon.2022.100665  

   Mazenc, Frédéric ; Malisoff, Michael ( November 2022 , European Journal of Control)
4. Liquid Plasma Crystals on the ISS

   https://doi.org/10.2514/6.2023-2615  

   Kostadinova, Evdokiya G. ; Gehr, Emerson ; Andrew, Bradley ; Matthews, Lorin S. ; Hyde, Truell W. ; Terrell, Abbie ( January 2023 , American Institute of Aeronautics and Astronautics)

   This study examines the structure and stability of filamentary dusty plasmas using data from the Plasmakristall-4 (PK-4) facility on board the International Space Station. Under the action of a polarity-switched DC electric field, the dust particles in the PK-4 discharge have been found to organize into field-aligned extended filaments, which has been compared to the filamentary state in electrorheological (ER) fluids. Here we discuss how, in addition to an ER-type structural transition, the PK-4 dusty plasmas exhibit structural states reminiscent of those observed in liquid crystals (LCs) with rod-shaped molecules. We find that dust particles within the filaments are strongly coupled in a crystalline-like structure, while the coupling of particles across filaments is liquid-like. In addition to a common orientation along a director axis (nematic behavior), the dust filaments also appear to align in large-scale nested structures, or shells (smectic behavior). Finally, these filaments are found to further arrange in hexagonal patterns within the plane orthogonal to the director axis, suggesting the possibility for smectic-B and smectic-C structural states. As the observed ER and LC features of the filamentary dusty plasma states are sensitive to variations in the PK-4 discharge conditions, we argue that these dusty plasmas can provide a controlled analogous system for the study of fundamental phenomena in soft matter, such as the origins of pattern formation and universality of phase transitions. 

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5. Asymmetric Sawtooth Microstructure Induced Vapor Mobility for Suppressed Buoyancy Conditions: Terrestrial Experiment and Design for ISS Experiments

   https://doi.org/10.1109/TCPMT.2021.3104467  

   Sridhar, Karthekeyan ; Narayanan, Vinod ; Bhavnani, Sushil H. ( October 2021 , IEEE Transactions on Components, Packaging and Manufacturing Technology)

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