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1. Indenting glasses with indenters of varying stiffness and sharpness

   https://doi.org/10.1016/j.jnoncrysol.2022.122111  

   Christensen, Johan F.S.; Krishnan, N.M. Anoop; Bauchy, Mathieu; Smedskjaer, Morten M. (March 2023, Journal of Non-Crystalline Solids)
2. Time-Varying Queues

   Whitt, Ward (January 2018, Queueing models and service management)

   Service systems abound with queues, but the most natural direct models are often time-varying queues, which may require nonstandard analysis methods beyond stochastic textbooks. This paper provides an overview of time-varying queues. Most of the recent literature concerns many-server queues, which arise in large-scale service systems, such as in customer contact centers and hospital emergency departments, but there also has been some new work on single-server queues with time-varying arrivals, which arise in some settings, such as airplanes coming to land at an airport, cars coming to a traffic intersection and medical staff waiting for the availability of special operating rooms in a hospital. The understanding of many-server queues and single-server queues is enhanced by heavy-traffic limits, which have been extended to time-varying models as well as stationary models. 

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3. Time-Varying Robust Queueing

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   Whitt, Ward; You, Wei (September 2019, Operations Research)
4. Impact of strongback on structure with varying damper and stiffness irregularity arrangements

   https://doi.org/10.1016/j.jcsr.2023.108333  

   Abolghasemi, Sima; Wierschem, Nicholas E.; Denavit, Mark D. (February 2024, Journal of Constructional Steel Research)

   Structures susceptible to soft story mechanisms are particularly vulnerable to earthquakes because damage concentrated at a single story can lead to premature failure of the structure. The strongback, a stiff vertical spine pinned at the structure’s base and running its height, has been proposed as a way to impose a more uniform pattern of floor displacements and prevent soft story mechanisms. However, changes in the impact of strongbacks on the performance of structures remain unclear when considering vertical stiffness irregularities at different positions along the height of a structure and different arrangements of energy dissipation devices in a structure. This study aims to address these gaps through an extensive parametric experimental investigation varying the location of vertical stiffness irregularities and the arrangement of dampers in a small-scale four-story elastic structure with and without a strongback. For this study, each configuration of the structure is loaded with shake table-produced seismic ground motion. The results of this study show that, regardless of which story a stiffness irregularity is located, the strongback significantly reduces the maximum story drift in the structure. Furthermore, with the strongback, the maximum story and roof drift are insensitive to damper position and distribution, whereas, without it, the damper position significantly impacts the structural performance. The strongback’s ability to protect against soft story vertical irregularities, regardless of their locations, and the insensitivity of structural performance to damper arrangement when utilizing a strongback, presents promising new options for structural design, architectural design, and remediation efforts. 

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5. Robustness analysis of uncertain time‐varying systems using integral quadratic constraints with time‐varying multipliers

   https://doi.org/10.1002/rnc.5299  

   Fry, J. Micah; Abou Jaoude, Dany; Farhood, Mazen (December 2020, International Journal of Robust and Nonlinear Control)

   Summary This article presents a dissipativity approach for robustness analysis using the framework of integral quadratic constraints (IQCs). The derived results apply for linear time‐varying nominal systems with uncertain initial conditions. IQC multipliers are used to describe the sets of allowable uncertainty operators, and signal IQC multipliers are used to describe the sets of allowable disturbance signals. The novel concepts of dichotomic nodes and their corresponding factorizations are introduced, which allow for the aforementioned multipliers to be general time‐varying operators. The results are illustrated via the robustness analysis of a flight controller for an unmanned aircraft system tasked to perform a Split‐S maneuver. 

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