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The Virtual Watershed Client, built using the Unity game engine, provides a tool that allows researchers, students, and others to observe and analyze geospatial datasets and theoretical model data acquired from the Virtual Watershed Platform. The Virtual Watershed Platform is used as a service to acquire data that is used by the Virtual Watershed Client to create terrain, satellite imagery, shapes,...
Low density parity check (LDPC) codes with iterative soft decoding have been adopted as the primary error correction coding technology in data storage devices, e.g., hard disk drives (HDDs) and solid state drives (SSDs). Data storage normally has stringent requirements for low probability of decoding failure since there is no re-transmission mechanism as available for most other data communication...
It is known that increased levels of exchange generally reduce the coercivity of thin-film granular magnetic media. However, this behavior cannot be derived from simple mean field theory. Irrespective of whether grains switch individually or are located on the edge of a domain propagating through the medium, a critical grain tends to see equal numbers of positively and negatively polarized grains...
Optimization of magnetic read widths (MRWs) and reader positioning in two dimensional magnetic recording (TDMR) are explored. The optimization is based on waveforms from 511-bit maximal-length pseudo-random binary sequence (PRBS) patterns. The TDMR error rates are determined from a large ensemble of full micromagnetic simulations. Each simulation involves writing three overlapping tracks in a shingled...
The class of systems know as VTOL vehicles encapsulates a wide variety of real world systems of interest including helicopters, jets and unmanned aerial vehicles. These VTOL vehicles exhibit heavily nonlinear dynamics. Consequently, nonlinear control techniques are required to achieve global stabilisation. Often, VTOL vehicles are stabilised using nonlinear cascade techniques. However, if care is...
In this paper, we propose a high performance, Lyapunov based control design for symmetric VTOL vehicles to track trajectories at which aerodynamic effects are significant. We consider the case where an accurate model of aerodynamic forces may be obtained either analytically or empirically. A Lyapunov based control strategy is proposed. To avoid lengthy and noisy control expressions resulting from...
The increasing effects of climate change and extreme weather events on the operation of power systems highlight the need for developing effective techniques and models for evaluating the challenges that power systems may have to deal with in the future for maintaining high levels of resilience. Within this context, the aim of the `Resilient Electricity Networks for Great Britain (RESNET)' project...
Graph separators are a ubiquitous tool in graph theory and computer science. However, in some applications, their usefulness is limited by the fact that the separator can be as large as Ω(?n) in graphs with n vertices. This is the case for planar graphs, and more generally, for proper minor-closed families. We study a special type of graph separator, called a layered separator, which...
This paper presents a new modelling framework, the Harmonic State-Space (HSS). The new framework is intended for stability analysis of electromagnetic or control interactions between interconnected power electronic systems. Existing modelling methods are summarised, highlighting their advantages and disadvantages. The HSS provides a framework to accommodate non-linear power electronic circuits that...
This paper presents a Harmonic State-Space (HSS) model of a fixed delay angle six-pulse High Voltage Direct Current (HVdc) converter. Under the HSS modelling framework, the non-linear switching of the converter thyristors is linearised using a small-signal modelling technique, and described by Frequency Transfer Matrices (FTM). The HSS is an extension to the Harmonic Domain (HD); it captures signal...
This paper studies the performance of a serial turbo code on two simplified rectangular-grain models of recording media for two dimensional magnetic recording at a density of more than 0.5 bits/grain. We derive one-dimensional (1D) and two-dimensional (2D) rectangular-grain media models and from these present finite-state-machine (FSM) representations. From the FSM for the 1D model we computed achievable...
We previously reported Compton imaging measurements of 137Cs and 60Co laboratory sources using the full 15-channel readout of the Gamma-Ray Experimental Telescope Assembly (GRETA). We have since modified the detector geometry to accommodate a wider range of Compton scattering angles and implemented a neural networking method for the location of interaction positions with a 3-cm resolution inside the...
This paper presents a harmonic state-space model of a three-phase thyristor controlled reactor. In this description, both the transient and steady-state response of individual harmonics are quantified. The results were validated using a strictly time-domain simulation. A further development of the model is the use of characteristic harmonics of the power converter to reduce the number of harmonics...
Summary form only given. Arrays of Si PIN diodes are fielded on radiation producing experiments on the Shiva Star pulsed power generator at AFRL's Directed Energy Directorate. This work is a continuation of earlier work done on Shiva Star. Each diode is filtered to respond to a part of the band of interest and the signals are then deconvolved to generate the radiation spectrum as a function of time...
Summary form only given. Experiments on FRC formation and translation into the interior of a metal shell or liner have been conducted at AFRL. Flux exclusion, collimated light, and interferometer data on magnetized plasma injection will be presented. These are a pre-requisite for FRC compression by liner implosion, experiment progress on which will also be presented. FRC translation, capture, and...
In classical harmonic domain (HD) modelling, a frequency transfer matrix is used to describe the frequency coupling across a power electronics device. This is normally based on switching functions using pre-defined switching instants. These are usually arrived at via an iterative process. In extending HD to Harmonic State-Space (HSS) where transient harmonic variation can be modelled, it is imperative...
As universities have seen their role rapidly evolve in the last two decades, they have learned to respond differently to their immediate economic context. However, not all universities have been equally successful in developing the capabilities that their new role demands. Many institutional, cultural and structural factors make this change difficult. In order to develop new capabilities and entrepreneurial...
For a new class of soft robotic platforms, development of flexible and robust actuators is quintessential. Remarkable resilience, shape memory effect, high energy density, and scalability are attributed to nickel titanium (NiTi) making it an excellent actuator candidate for meso-scale applications. This paper presents a micro-muscle fiber crafted from shape memory alloy (NiTi) coiled springs. An enhanced...
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