Abstract: Carbon nanotube foams are provided which comprise tubes substantially aligned longitudinally in a first direction, wherein: each tube defines an outer wall and an inner wall, and each tube comprises an entangled bundle of carbon nanotubes substantially aligned longitudinally in the first direction; and tubes in at least a subset of the tubes are positioned with respect to each other to form one or more first hexagonal units, wherein each first hexagonal unit comprises first-hexagonal-unit tubes, wherein the first-hexagonal-unit tubes comprise six peripheral first-hexagonal-unit tubes and a central first-hexagonal-unit tube, wherein the six peripheral first-hexagonal-unit tubes surround the central first-hexagonal-unit tube in a juxtaposed, hexagonal configuration. Articles of manufacture, e.g., helmets, comprising the foams are also provided which are configured to cover at least a portion of an object, e.g.

Abstract: One or more computing devices, systems, and/or methods are provided. In an example, a method includes tuning a sensor comprising a first resonator having an effective gain, a second resonator having an effective loss, and a coupling circuit connected between the first resonator and the second resonator at an extrema degeneracy point with a nonlinear response to a force applied to the sensor. At least one of the first resonator, the second resonator, or the coupling circuit comprises a variable capacitor having a capacitance that varies as a function of the force. The method comprises injecting an input signal into one of the first resonator or the second resonator, receiving an output signal from one of the first resonator or the second resonator, and determining a magnitude of a force based on a difference between a first frequency extrema point and a second frequency extrema point in the output signal.

Abstract: Carbon-based composite materials are provided, such as those comprising at least 80 weight % of graphitic carbon comprising functional groups capable of forming hydrogen bonds, the graphitic carbon in the form of a mat of randomly entangled elongated structures; not more than 20 weight % of a polymer or a nanofiber thereof, dispersed within the graphitic carbon, the polymer or the nanofiber thereof comprising corresponding functional groups capable of forming hydrogen bonds with the functional groups of the graphitic carbon; and a plurality of hydrogen bonds at an interface formed between the graphitic carbon and the polymer or the nanofiber thereof, the plurality of hydrogen bonds formed between the functional groups of the graphitic carbon and the corresponding functional groups of the polymer or the nanofiber thereof.