Nonlinearity Management in Optics: Experiment, Theory, and Simulation

We conduct an experimental investigation of nonlinearity management in optics using femtosecond pulses and layered Kerr media consisting of glass and air. By examining the propagation properties over several diffraction lengths, we show that wave collapse can be prevented. We corroborate these experimental results with numerical simulations of the (2+1)-dimensional focusing cubic nonlinear Schrödinger equation with piecewise constant coefficients and a theoretical analysis of this setting using a moment method

Counterparty Credit Limits: An Effective Tool for Mitigating Counterparty Risk?

A counterparty credit limit (CCL) is a limit imposed by a financial institution to cap its maximum possible exposure to a specified counterparty. Although CCLs are designed to help institutions mitigate counterparty risk by selective diversification of their exposures, their implementation restricts the liquidity that institutions can access in an otherwise centralized pool. We address the question of how this mechanism impacts trade prices and volatility, both empirically and via a new model of trading with CCLs. We find empirically that CCLs cause little impact on trade. However, our model highlights that in extreme situations, CCLs could serve to destabilize prices and thereby influence systemic risk

Testing of disability identification tool for schools

There has been an ongoing concern about the lack of reliable data on disabled children in schools. To date there has been no consistent way of identifying and categorising disabilities. Schools in England are currentlyrequired to collect data on children with Special Educational Need (SEN), but this does not capture information about all disabled children. The lack of this information may seriously restrict capacity at all levels of policy and practice to understand and respond to the needs of disabled children and their families in line with Disability Discrimination Act (2005) and the single Equality Act (2010). The aim of the project was to test the draft tools for identifying disability and accompanying guidance in a sample of all types of maintained schools in order to assess their usability and reliability and whether they resulted in the generation of robust and consistent data that could reliably inform school returns for the annual School Census

Navigating Uncertainty in Automotive Technology Instruction: The Subjective Experiences of Automotive Instructors During Laboratory Activities

Educational researchers have conducted very few studies on the subjective experiences of both trained and self-taught auto mechanics (Barber, 2003, 2004; Nelsen, 1997, 2010). Further, no present studies explore the subjective experience of the automotive instructor as he or she experiences uncertainty in the automotive lab. This study addresses a gap in the current literature on career/technical instructor development. For this study, data were gathered by video recording automotive laboratory activities at three Midwestern automotive programs. Interpersonal Process Recall (IPR) interviews were conducted with automotive instructors as they observed themselves navigating the lab environment. Data from the IPR interviews were analyzed using emergent thematic analysis. The research revealed that most instructors in this study were aware, after reflection, of the reasoning behind many of the intuitive and improvisational behaviors, and had an awareness of the nuances of skill assessment the importance of modeling behavior. This study also identified transfer of artistry as a concept of advanced skill attainment in automotive subjects. Transfer of artistry is the result of an instructor’s ability to manage several paradigms of the laboratory experience at once, to create the appropriate conditions for a student to develop the cognitive, spatial, and tactile skills necessary for performing advanced automotive diagnostics and repair. This dissertation is available in open access at AURA: Antioch University Repository and Archive, http://aura.antioch.edu/ and OhioLINK ETD Center, https://etd.ohiolink.ed

The DM Environment: From Annotation to Dissemination

DM (formerly Digital Mappaemundi) is an online environment that allows users to easily assemble collections of images and texts for study, produce their own rich analysis data, and publish online resources for individual, group or public use. DM is ready for multi-year work with five partner projects (including a new partnership with the British Library) to implement a publicly available user-friendly environment that enables users to 1) assemble collections of resources from any combination of accessible repositories; 2) create richly linked data (e.g., annotation networks involving combinations of images, texts, fragments, web resources, and other annotations) and collections, sequences and indices that organize this data; 3) export data in a number of linked data formats; and 4) easily produce publicly accessible and interactive websites based on such data and linked data published elsewhere

Modeling Broadband Ocean Acoustic Transmissions with Time-Varying Sea Surfaces

Solutions to ocean acoustic scattering problems are often formulated in the frequency domain, which implies that the surface is frozen in time. This may be reasonable for short duration signals but breaks down if the surface changes appreciably over the transmission time. Frequency domain solutions are also impractical for source-receiver ranges and frequency bands typical for applications such as acoustic communications (e.g. hundreds to thousands of meters, 1-50 kHz band). In addition, a driving factor in the performance of certain acoustic systems is the Doppler spread, which is often introduced from sea-surface movement. The time-varying nature of the sea surface adds complexity and often leads to a statistical description for the variations in received signals. A purely statistical description likely limits the insight that modeling generally provides. In this paper, time-domain modeling approaches to the sea-surface scattering problem are described. As a benchmark for comparison, the Helmholtz integral equation is used for solutions to static, time-harmonic rough surface problems. The integral equation approach is not practical for time-evolving rough surfaces and two alternatives are formulated. The first approach is relatively simple using ray theory. This is followed with a ray-based formulation of the Helmholtz integral equation with a time-domain Kirchhoff approximation