Bistable Helmholtz dark spatial optical solitons in materials with self-defocusing saturable nonlinearity

We present, to the best of our knowledge, the first exact dark spatial solitons of a nonlinear Helmholtz equation with a self-defocusing saturable refractive-index model. These solutions capture oblique (arbitrary-angle) propagation in both the forward and backward directions, and they can also exhibit a bistability characteristic. A detailed derivation is presented, obtained by combining coordinate transformations and direct-integration methods, and the corresponding solutions of paraxial theory are recovered asymptotically as a subset. Simulations examine the robustness of the new Helmholtz solitons, with stationary states emerging from a range of perturbed input beams

Opinion Cascades and Echo-Chambers in Online Networks: A Proof of Concept Agent-Based Model

In online networks, the polarization of opinions (e.g., regarding presidential elections or referenda) has been associated with the creation of “echo-chambers” of like-minded peers, secluded from those of contrary viewpoints. Previous work has commonly attributed such phenomena to self-regarding preferences (e.g., confirmation bias), individual differences, and the pre-dispositions of users, with clusters forming over repeated interactions. The present work provides a proof of concept Agent-Based Model that demonstrates online networks are susceptible to echo-chambers from a single opinion cascade, due to the spatiotemporal order induced by lateral transmission. This susceptibility is found to vary as a function of degree of interconnectivity and opinion strength. Critically, such effects are found despite globally proportionate levels of opinions, equally rational agents (i.e. absent conformity, confirmation bias or pre-disposition architecture), and prior to cyclical interactions. The assumptions and implications of this work, including the value of Agent-Based Modelling to cognitive psychology, are discussed

Feature importances estimated by Random Forest with 1000 trees with the Best Ankle + Best Hip feature set and the segmentation strategy of 180s windows with 120s overlap.

<p>Feature importances estimated by Random Forest with 1000 trees with the Best Ankle + Best Hip feature set and the segmentation strategy of 180s windows with 120s overlap.</p

Number of instances per dataset and segmentation strategy.

<p>Number of instances per dataset and segmentation strategy.</p

Algorithm for feature extraction, selection and classification.

<p>Algorithm for feature extraction, selection and classification.</p

Exemplary raw accelerometer readings for one hour during which two participants, (a) male and (b) female, had a jogging activity.

<p>The inclinometer and number of steps time series are not shown for clarity because they are in a different unit with much smaller values. Jogging ‘diary’ relates to the reported jogging period by the user. Jogging ‘golden’ is the jogging period per the ‘golden standard’ labels.</p

Performance of different classifiers on the 4 final feature sets, depending on feature type with the segmentation strategy of 60s windows without overlap.

<p>Performance of different classifiers on the 4 final feature sets, depending on feature type with the segmentation strategy of 60s windows without overlap.</p

Distribution of participants and Jogging Periods (JP) duration in minutes per dataset.

<p>Distribution of participants and Jogging Periods (JP) duration in minutes per dataset.</p

Performance of different classifiers on the 4 final feature sets, depending on feature type with the segmentation strategy of 180s windows with 120s overlap.

<p>Performance of different classifiers on the 4 final feature sets, depending on feature type with the segmentation strategy of 180s windows with 120s overlap.</p

Population characteristics.

<p>Mean (standard deviation) unless otherwise stated.</p