Swipe dynamics as a means of authentication: results from a Bayesian unsupervised approach

The field of behavioural biometrics stands as an appealing alternative to more traditional biometric systems due to the ease of use from a user perspective and potential robustness to presentation attacks. This paper focuses its attention to a specific type of behavioural biometric utilising swipe dynamics, also referred to as touch gestures. In touch gesture authentication, a user swipes across the touchscreen of a mobile device to perform an authentication attempt. A key characteristic of touch gesture authentication and new behavioural biometrics in general is the lack of available data to train and validate models. From a machine learning perspective, this presents the classic curse of dimensionality problem and the methodology presented here focuses on Bayesian unsupervised models as they are well suited to such conditions. This paper presents results from a set of experiments consisting of 38 sessions with labelled victim as well as blind and over-the-shoulder presentation attacks. Three models are compared using this dataset; two single-mode models: a shrunk covariance estimate and a Bayesian Gaussian distribution, as well as a Bayesian non-parametric infinite mixture of Gaussians, modelled as a Dirichlet Process. Equal error rates (EER) for the three models are compared and attention is paid to how these vary across the two single-mode models at differing numbers of enrolment samples.Comment: 9 pages, 7 figures; Layout and editing improve

New York City Pre-K Leadership Study

Presents key findings from a study of New York City pre-K leaders that evaluated how leaders support teachers and what factors help or hinder leaders’ efforts to positively impact learning for all children.https://educate.bankstreet.edu/faculty-staff/1042/thumbnail.jp

The Center on Culture, Race & Equity: A Case Study on Systemic Change

This video offers a look at the Bank Street Center on Culture, Race & Equity’s partnership with District of Columbia Public Schools to address educational disparities for African American boys. The center’s work focused on helping school staff examine their own implicit biases, stereotypes, and microaggressions and learn to shift from deficit- to strengths-based attitudes to support system level change.https://educate.bankstreet.edu/faculty-staff/1038/thumbnail.jp

Hamiltonian mappings and circle packing phase spaces

We introduce three area preserving maps with phase space structures which resemble circle packings. Each mapping is derived from a kicked Hamiltonian system with one of three different phase space geometries (planar, hyperbolic or spherical) and exhibits an infinite number of coexisting stable periodic orbits which appear to `pack' the phase space with circular resonances.Comment: 23 pages including 12 figures, REVTEX

Testing morphodynamic controls on the location and frequency of river avulsions on fans versus deltas: Huanghe (Yellow River), China

A mechanistic understanding of river avulsion location and frequency is needed to predict the growth of alluvial fans and deltas. The Huanghe, China, provides a rare opportunity to test emerging theories because its high sediment load produces regular avulsions at two distinct nodes. Where the river debouches from the Loess plateau, avulsions occur at an abrupt decrease in bed slope and reoccur at a time interval (607 yrs) consistent with a channel-filling timescale set by the superelevation height of the levees. Downstream, natural deltaic avulsions reoccur at a timescale that is fast (7 yrs) compared to channel-filling timescale due to large stage-height variability during floods. Unlike the upstream node, deltaic avulsions cluster at a location influenced by backwater hydrodynamics and show evidence for episodic downstream migration in concert with progradation of the shoreline, providing new expectations for the interplay between avulsion location, frequency, shoreline rugosity and delta morphology

POST- ensemble: workshop and performance at the 'Electronics Symposium'.

POST— is an experimental music ensemble focused on synths, electronics and noise making—exploring how small interactions between players can have a large cumulative effect. Workshop participants were given improvisatory and listening exercises and together devised two pieces that they performed to an audience in the evening portion of the event. The electronics Symposium was a two day event funded by Arts Council England, FEAST and the Cornwall Community Foundation

Origin of a preferential avulsion node on lowland river deltas

River deltas are built by cycles of lobe growth and abrupt channel shifts, or avulsions, that occur within the backwater zone of coastal rivers. Previous numerical models differ on the origin of backwater‐scaled avulsion nodes and their consistency with experimental data. To unify previous work, we developed a numerical model of delta growth that includes backwater hydrodynamics, river mouth progradation, relative sea level rise, variable flow regimes, and cycles of lobe growth, abandonment, and reoccupation. For parameter space applicable to lowland deltas, we found that flow variability is the primary mechanism to cause persistent avulsion nodes by focusing aggradation within the backwater zone. Backwater‐scaled avulsion nodes also occur under less likely scenarios of initially uniform bed slopes or during rapid relative sea level rise and marine transgression. Our findings suggest that flow variability is a fundamental control on long‐term delta morphodynamics

Surging Versus Continuous Turbidity Currents: Flow Dynamics and Deposits in an Experimental Intraslope Minibasin

Small intraslope basins (~100 km^2), or "minibasins," such as those found on the continental slope of the Gulf of Mexico, have been filled predominantly by turbidity currents. Each minibasin is the result of local subsidence and is partially or completely isolated from neighboring basins by ridges formed from compensational uplift. We undertook a series of experiments to investigate the relationship between the flow dynamics of turbidity currents entering a minibasin and the stratal architecture of their deposits. The experiments were performed using continuous-feed turbidity currents and surge-feed turbidity currents. A dimensionless ponding number is developed to compare the geometry of the deposits with the dynamics of the flows that filled the basins. The experimental surging turbidity currents created a deposit that was notably more ponded than the deposits of continuous turbidity currents