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We investigate quasi-two-dimensional buckled colloidal monolayers on a triangular lattice with tunable depletion interactions. Without depletion attraction, the experimental system provides a colloidal analog of the well-known geometrically frustrated Ising antiferromagnet [Y. Han et al., Nature 456, 898–903 (2008)]. In this contribution, we show that the added depletion attraction can influence both the magnitude and sign of an Ising spin coupling constant. As a result, the nearest-neighbor Ising “spin” interactions can be made to vary from antiferromagnetic to para- and ferromagnetic. Using a simple theory, we compute an effective Ising nearest-neighbor coupling constant, and we show how competition between entropic effects permits for the modification of the coupling constant. We then experimentally demonstrate depletion-induced modification of the coupling constant, including its sign, and other behaviors. Depletion interactions are induced by rod-like surfactant micelles that change length with temperature and thus offer means for tuning the depletion attraction in situ. Buckled colloidal suspensions exhibit a crossover from an Ising antiferromagnetic to paramagnetic phase as a function of increasing depletion attraction. Additional dynamical experiments reveal structural arrest in various regimes of the coupling-constant, driven by different mechanisms. In total, this work introduces novel colloidal matter with “magnetic” features and complex dynamics rarely observed in traditional spin systems. 

Recently, switched Ethernet has become increasingly popular in networked cyber-physical systems (NCPS). In an Ethernet-based NCPS, network-connected devices (e.g., sensors and actuators) realize time-critical tasks by exchanging miscellaneous information, such as sensor readings and control commands. To ensure reliable control and operation, network-induced delays for time-critical NCPS applications must be carefully examined. In this work, we propose a framework combining network delay measurements and network-calculus-based delay performance analysis to obtain accurate, deterministic worst-case delay bounds for NCPS. By modeling traffic sources and networking devices (e.g., Ethernet switches) through measurements, we establish accurate traffic and device models for network-calculus-based analysis. To obtain worst-case delay bounds, different network-calculus-based analytical methods can be leveraged, allowing CPS architects to customize the proposed delay analysis framework to suit application-specific needs. Our evaluation results show that the proposed approach derives accurate delay bounds, making it a valuable tool for architects designing NCPSs supporting time-critical applications. 

In this work, we propose to derive realistic, accurate bounds on network-induced delays for time-critical tasks running on Avionics Full-Duplex Switched Ethernet. In the WiP poster, we present preliminary evaluation results showing that through measurement-based modeling and refining network-calculus-based analysis with measurements, tight delay bounds can be obtained for AFDX networks with realistic traffic patterns and network workloads. 

When stressed sufficiently, solid materials yield and deform plastically via reorganization of microscopic constituents. Indeed, it is possible to alter the microstructure of materials by judicious application of stress, an empirical process utilized in practice to enhance the mechanical properties of metals. Understanding the interdependence of plastic flow and microscopic structure in these nonequilibrium states, however, remains a major challenge. Here, we experimentally investigate this relationship, between the relaxation dynamics and microscopic structure of disordered colloidal solids during plastic deformation. We apply oscillatory shear to solid colloidal monolayers and study their particle trajectories as a function of shear rate in the plastic regime. Under these circumstances, the strain rate, the relaxation rate associated with plastic flow, and the sample microscopic structure oscillate together, but with different phases. Interestingly, the experiments reveal that the relaxation rate associated with plastic flow at time t is correlated with the strain rate and sample microscopic structure measured at earlier and later times, respectively. The relaxation rate, in this nonstationary condition, exhibits power-law, shear-thinning behavior and scales exponentially with sample excess entropy. Thus, measurement of sample static structure (excess entropy) provides insight about both strain rate and constituent rearrangement dynamics in the sample at earlier times.