Reconfigurable Floquet elastodynamic topological insulator based on synthetic angular momentum bias

Originating with the discovery of the quantum Hall effect (QHE) in condensed matter physics, topological order has been receiving increased attention also for classical wave phenomena. Topological protection enables efficient and robust signal transport; mechanical topological insulators (TIs), in particular, are easy to fabricate and exhibit interfacial wave transport with minimal dissipation, even in the presence of sharp edges, defects, or disorder. Here, we report the experimental demonstration of a phononic crystal Floquet TI (FTI). Hexagonal arrays of circular piezoelectric disks bonded to a PLA substrate, shunted through negative electrical capacitance, and manipulated by external integrated circuits, provide the required spatiotemporal modulation scheme to break time-reversal symmetry and impart a synthetic angular momentum bias that can induce strong topological protection on the lattice edges. Our proposed reconfigurable FTI may find applications for robust acoustic emitters and mechanical logic circuits, with distinct advantages over electronic equivalents in harsh operating conditions.

A cutting edge 6U CubeSat ADCS design for Earth observation with sub-meter spatial resolution at 230–380 km altitude

A 6U CubeSat for Earth observation in 230–350 km orbits with sub-meter resolution is presented. The proposed Stable and Highly Accurate Pointing Earth-Imager (SHAPE) system’s attitude determination and control system (ADCS) is composed of a single momentum bias wheel with magnetic bearings at rotational speeds of 6000–7000 rpm and refined magnetorquers. Reaction wheels as instability source are absent. The ADCS stabilizes the spacecraft attitude by counteracting the torques from external disturbances in the thermosphere down to < 1° pointing accuracy and < 0.1° instability. The momentum wheel was sized to an angular momentum of 1 Nms based on the worst-case atmospheric density of the next solar cycle. The 0.5 Am2 magnetorquer dipole moment provides with low power consumption, mass and cost, high reliability and sufficient torque. The ADCS initialisation study revealed three stable start-up modes, while the all-spun state is achieved using a set of thrusters. De-tumbling analysis show that the magnetorquers reduce the tumbling rates with magnitudes of up to 35°/s to mean motion values in less than an orbit using a static gain B-dot controller. A 3U camera design capable of sub-meter spatial resolution at 230 km altitude is presented which complies with the SHAPE spacecraft system design. The instrument has a single deployable primary mirror enabled by a deployment hinge design with hysteresis < 0.5 μ. This payload combined with air-breathing electric propulsion technology at 230 km nominal altitude boosts the SHAPE system Earth observation potential down to sub-meter spatial resolution and enables tuning of the mission lifetime by orbit keeping.

A simulation-based approach to training in heuristic clinical decision-making

Background Cognitive biases may negatively impact clinical decision-making. The dynamic nature of a simulation environment can facilitate heuristic decision-making which can serve as a teaching opportunity. Methods Momentum bias, confirmation bias, playing-the-odds bias, and order-effect bias were integrated into four simulation scenarios. Clinical simulation educators and human factors specialists designed a script of events during scenarios to trigger heuristic decision-making. Debriefing included the exploration of frames (mental models) resulting in the observed actions, as well as a discussion of specific bias-prone frames and bias-resistant frames. Simulation sessions and debriefings were coded to measure the occurrence of bias, recovery from biased decision-making, and effectiveness of debriefings. Results Twenty medical residents and 18 medical students participated in the study. Twenty pairs (of one medical student and one resident) and two individuals (medical residents alone) completed a simulation session. Evidence of bias was observed in 11 of 20 (55%) sessions. While most participant pairs were able to avoid or recover from the anticipated bias, there were three sessions with no recovery. Evaluation of debriefings showed exploration of frames in all the participant pairs. Establishing new bias-resistant frames occurred more often when the learners experienced the bias. Conclusions Instructional design using experiential learning can focus learner attention on the specific elements of diagnostic decision-making. Using scenario design and debriefing enabled trainees to experience and analyze their own cognitive biases.