USA As Represented by Secretary of the Navy

Jonathan M Nichols

Frank Bucholtz

Gustavo Kunde Rohde

Geoffrey A Cranch

Meredith N Hutchinson

Mark Seaver

Nicole Menkart

Methods, apparatuses, and systems for calculating time delays by a Wasserstein approach are provided. A plurality of signals are recorded by a plurality of sensors (three or more), respectively, and received at a controller. The plurality of signals recorded by the plurality of sensors are generated in response to a signal emitted by a source. The plurality of signals are converted into a plurality of probability density functions. A cumulative distribution transform for each of the plurality of probability density functions is calculated. A time delay for each unique pair of the plurality of sensors is calculated by minimizing a Wasserstein distance between two cumulative distribution transforms corresponding to the unique pair of the plurality of sensors.

Methods, apparatuses and systems for time delay estimation

A photonic compressive sampling system includes a photonic link with at least one electro-optic modulator that modulates a continuous wave optical energy with both an electrical analog signal and a pseudorandom bit sequence signal. A photodetector receives the modulated optical energy from the electro-optic modulator, and an electrical digitizer digitizes the output from the photodetector. The system enables signal recovery beyond the Nyquist limit of the digitizer. The signal being recovered has a sparse (low-dimensional) representation and the digitized samples are incoherent with this representation. An all-photonic system can faithfully recover a 1 GHz harmonic signal even when digitizing at 500 MS/s, well below the Nyquist rate.

System and method for photonic compressive sampling

A system and method for encoding zero and one bits for transmission, including generating a first signal from a non-linear chaotic system to represent the one bit, with the signal's embedded vectors being within the non-linear system's attractor set, and generating a second signal from the non-linear system to represent the zero bit, with the signal's embedded vectors being outside the non-linear system's attractor set. The second signal encoding the zero bit can be generated by adding together two chaotic signals arising from the non-linear system initialized with different initial conditions, and weighting the second signal to have approximately the same energy as the first signal. One suitable chaotic systems is a Lorenz system. Systems and methods for decoding a transmitted stream of signals compare a detection statistic of the received stream of signals to a threshold value that depends on the chaotic system.

Method and apparatus for secure digital communications using chaotic signals

A method including providing time series structural response data from a structure. A plurality of linear surrogate data series is generated from the time series structural response data. A first generalized correlation function is estimated for each linear surrogate data series of the plurality of linear surrogate data series to generate a confidence interval. The same correlation function is estimated for the time series structural response data. The output of the generalized correlation function applied to the structural response data is compared to the confidence interval. A damage-induced nonlinearity in the structure is indicated when the output of the generalized correlation function applied to the structural response data is outside of the confidence interval.

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Crofton, MD, United States of America

Jonathan M Nichols