North Central State College

An equivalent continuum model is developed for 2D and 3D square deployable space trusses consisting of composite Collapsible Tubular Mast (CTM) members. The repetitive nature of these structures allow for the utilization of single unit cell geometries in deriving effective stiffness and mass properties through energy equivalence, which are then compatible with continuous structural analysis such as standard beam theory. This provides an efficient method of approximating the global structural performance over a large parameter space for design optimization. Finite element analysis (FEA) in Abaqus/Standard models the CTM members as beam elements with direction dependent stiffnesses. End moment releases on the beam elements simulate how the CTM members are joined together by bonding the ends in a flattened state. FEA is used validate the analytical natural frequencies of 2D and 3D square truss configurations including bending, longitudinal, torsional, and warping-shear vibration modes. It also characterizes how the 3D square face arrangement influences the vibration modes based on whether the diagonal members from adjacent faces share common joints. An FEA validated parametric analysis is then conducted to examine how variations in unit cell geometries and truss patterns influence the equivalent continuum vibration modes for 2D and 3D square trusses.

This work presents an origami-inspired deployable composite shell structure that allows crease-folded packaging while retaining self-deployability enabled by the shell curvature. The structure incorporates crease lines by locally dropping plies so that only a single 45 degree plainweave carbon fiber/epoxy layer remains as a flexible hinge. The crease is supplemented by thin polyurethane tape to accommodate near-flattened folding. To evaluate the folding and unfolding behaviors, column bending tests are performed on an origami tape spring with a central crease line and compared against an uncreased control tape spring and a creased flat coupon. The origami tape spring shows the highest axial force and bending moment in the folded state, driven by the large crease thickness and curvature effects, but displays a milder snap-through response during quasi-static unfolding. Dynamic deployment experiments reveal that the origami tape spring reliably self-unfolds, but retains a slower and more controlled deployment than the control tape spring. Importantly, peak-to-peak accelerations induced by shock events at the end of deployment is reduced by 74–79\%, demonstrating significant mitigation. Overall, integrating shell curvature with origami folding enables composite space structures that can be stowed in a near-flattened state, be self-deployable, and scalable in design with more complex fold patterns.

Our study investigates the deployment of Unmanned Aerial Vehicles (UAVs) in areas, such as mountainous regions, where installing terrestrial base stations (TBS) is challenging. This approach extends the coverage area of commercial network services, enhances network capacity, and ensures reliable internet service for ground users (GUs) in remote locations. However, a key challenge remains for terrestrial networks operating in licensed frequency bands, which limits the availability of physical resource blocks (PRBs). This constraint highlights the need for PRB sharing, which introduces interference issues. To address this challenge, we design a federated learning (FL) framework that enables all agents, such as GUs, UAVs, and TBS, to collaboratively learn by interacting with the physical network environment for intelligent dynamic spectrum sharing (DSS) to mitigate interference. Additionally, our FL framework optimizes the placement of UAVs for efficient deployment to maximize network throughput. It also allows GUs and UAVs to adjust their transmit power to achieve energy efficiency that addresses their limited battery storage constraints. To accomplish this, we formulate a mixed-integer nonlinear optimization framework with the objective of minimizing energy consumption while meeting service reliability constraints. The proposed FL framework tackles this optimization problem by transforming it into an unconstrained Markov Decision Process (UUMDP) problem. The GUs employ the asynchronous advantage actor-critic (A3C) algorithm to explore the optimal solution for this UUMDP problem that maintains the time complexity for local model computations even in large-scale network deployments. Additionally, the FL framework provides feedback on the knowledge of all learning agents through global model aggregation to improve local models. Simulation results demonstrate that our approach outperforms the multi-agent deep Q-networks (DQN) method in terms of energy efficiency and service reliability.

Military combat loading requires arranging equipment on maritime transport vessels to enable rapid, prioritized off-loading while maintaining unit cohesion and vessel stability. This paper extends a prioritized two-dimensional orthogonal packing framework to address the specific operational constraints of military logistics, incorporating global load balancing requirements alongside existing prioritization objectives. We introduce three solution techniques for this globally constrained problem: a monolithic mixed-integer linear programming (MILP) approach, a sliding-window matheuristic, and a sliding-window matheuristic with in-stride load balancing penalties. For any sliding-window solution that fails to achieve both feasible packing and load balancing in the initial stage, we develop a universal post-processing strategy that selectively relaxes and re-optimizes item positions to achieve balance with minimal disruption to the prioritized layout. Computational experiments demonstrate that the matheuristic approaches fundamentally outperform the monolithic MILP approach in load balance reliability, solution quality, and computational efficiency, providing practical guidance for integrating automated optimization into military load planning systems. The proposed methods generate high-quality, load-balanced solutions for single-vessel scenarios in approximately two minutes on average, enabling rapid evaluation of multiple loading configurations during time-critical deployment planning.

The assessment of the dynamic mechanical performance of fiber-reinforced composites has gained importance in specific high-tech applications like aerospace and automobiles. However, three dimensional (3D) auxetic reinforcements offering viable performance have remained unexplored. Hence, this study investigates the energy absorption capabilities and high strain impact behaviors of 3D woven fabric-reinforced composites. Three different types of 3D woven reinforcements i.e., warp interlock (Wp), weft interlock (Wt), and bidirectional interlock (Bi) were developed from jute yarn, and their corresponding composites were fabricated using polycarbonate (PC) and polyvinyl butyral (PVB). Out-of-plane auxeticity was measured for reinforcements while composites were analyzed under dynamic tests. Wp exhibited the highest auxeticity with a value of −1.29, Bi showed the least auxeticity with a value of −0.31, while Wt entailed an intermediate value of −0.46 owing to variable interlacement patterns. The dynamic mechanical analysis (DMA) results revealed that composite samples developed with PC resin showed a higher storage modulus with the least tan delta values less than 0.2, while PVB-based samples exhibited higher loss modulus with tan delta values of 0.6. Split Hopkinson pressure bar (SHPB) results showed that, under 2 and 4 bar pressure tests, PVB-based composites exhibited the highest maximum load while PC-based composites exhibited the least. Warp interlock-based composites with higher auxeticity showed better energy absorption when compared with the bidirectional interlock reinforcement based (with lower auxeticity) composites that exhibited lower peak load and energy dissipation.

In recent times, the wireless network market has received an influx of innovative technologies to cope up with the ever-growing data traffic demand and make efficient deployment and utilization of network resources. Despite that, cellular service and coverage in non-urban areas still remains largely unreliable. Providers predominantly set up roaming agreements to offer service to their customers in such regions where they have no coverage. These roaming services come with their own set of technical and operational constraints and limitations. As an alternative, we introduce <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Wireless Peering</i> for cellular providers, a concept inspired by ISP peering in wireline networks. By facilitating <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">settlement-free</i> spectrum sharing, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Wireless Peering</i> allows providers to seamlessly extend their coverage to off-network regions, without any hardware modifications. Due to its software-defined nature, the model offers high scalability, cost-effectiveness and ease of deployment. In this paper, we detail the core ideas and operational framework of a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Wireless Peering</i> model with a particular emphasis on improving customer satisfaction and provider revenue gains. Simulation results using <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OpencellID</i> data on real-life providers and customers across contiguous United States (US) exhibit significant improvements over roaming for both customers and providers.

ABSTRACT Mongolia's Eastern and Western Gobi Basins preserve a globally significant record of Cretaceous terrestrial vertebrates, yet their biostratigraphic correlations are complicated by a complex geological history. The Eastern Gobi Basin, a northeast‐southwest trending fault‐bounded rift system, includes several minor sub‐basins with distinct sedimentary sequences, notably the Upper Cretaceous Bayanshiree Formation. This formation hosts key localities of iconic taxa, including Segnosaurus , Erlikosaurus , Duonychus , Garudimimus , Amtocephale , Gobihadros and Adocus amtgai , yet previous correlations throughout the area lacked precision. Our sedimentological and stratigraphic campaigns (2022 to 2024) in the Bayanshiree Formation and overlying red‐bed sequences at Baishin Tsav refined these biostratigraphic and palaeoenvironmental frameworks. Field surveys at local (Baishin Tsav) and basin‐wide scales (Unegt and Zuunbayan sub‐basins) revealed a significant erosional unconformity dividing the formation into two distinct palaeoenvironmental stages: lower expansive erg (aeolian dunes) and upper mature fluvial floodplains. Additionally, this study redefines the previously misidentified red‐bed sequences above the Bayanshiree formation as the Javkhlant Formation (formerly Djadokhta or Baruungoyot formations). Taphonomic analyses indicate fossil assemblages were extensively reworked, demonstrating significant time‐averaging. This study provides evidence for climatic shifts through three successive environmental phases (erg, floodplain, alternating palaeosols) within the Bayanshiree and Javkhlant formations. These findings suggest widespread aridification in eastern Asia initiated during the Cenomanian–Turonian transition, contemporaneous with a subtropical high‐pressure shift and onset of the Cretaceous Thermal Maximum, challenging prior assumptions that placed this event later in the Late Cretaceous. This palaeoclimatic interpretation aligns with global records of past hyperthermal events and significantly refines the temporal context for interpreting regional palaeobiodiversity patterns.