Design of robust asynchronous reconfigurable controllers for parallel synchronization using embedded graphs

PhD Thesis: This is a revised version received 24/5/16. The definitive version is the print copy in the Research Reserve Collection of the University LibrarySynchronization is a key System-on-Chip (SoC) design issue in modern technologies. As the number of operating points under consideration increases, specifications which are capable of altering key parameters such as the time available for synchronization and Mean Time Between Failures (MTBF) in response to input from the user/system become desirable. This thesis explores how a combination of parallelism and scheduling, referred to as wagging, can be utilized to construct schedulers for synchronizer designs which are capable of pooling the gain-bandwidth products of their composite devices, in order to satisfy this requirement. In this work, we explore the ways in which the areas of graph theory and reconfigurable hardware design can be applied to generate both combinational and sequential scheduler designs, which satisfy the behavior requirement above. Further to this point, this work illustrates that such a scheduler is primarily comprised of an interrupt subsystem, and a reconfigurable token ring. This thesis explores how both of these components can be controlled in absence of a clock signal, as well as the design challenges inherent to each part. The final noteworthy issue in this study is with regard to the flow control of data in a parallel synchronizer that incorporates a First-In First-Out (FIFO) buffer to decouple the reading and writing operations from each other. Such a structure incurs penalties if the data rates on both sides are not well matched. This work presents a method by which combinations of serial and parallel reading operations are used to minimize this mismatch

Tangible language for hands-on play and learning

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 187-192).For over a century, educators and constructivist theorists have argued that children learn by actively forming and testing -- constructing -- theories about how the world works. Recent efforts in the design of "tangible user interfaces" (TUIs) for learning have sought to bring together interaction models like direct manipulation and pedagogical frameworks like constructivism to make new, often complex, ideas salient for young children. Tangible interfaces attempt to eliminate the distance between the computational and physical world by making behavior directly manipulable with one's hands. In the past, systems for children to model behavior have been either intuitive-but-simple (e.g. curlybot) or complex-but-abstract, (e.g. LEGO Mindstorms). In order to develop a system that supports a user's transition from intuitive-but-simple constructions to constructions that are complex-but-abstract, I draw upon constructivist educational theories, particularly Bruner's theories of how learning progresses through enactive then iconic and then symbolic representations. This thesis present an example system and set of design guidelines to create a class of tools that helps people transition from simple-but-intuitive exploration to abstract-and-flexible exploration. The Topobo system is designed to facilitate mental transitions between different representations of ideas, and between different tools. A modular approach, with an inherent grammar, helps people make such transitions. With Topobo, children use enactive knowledge, e.g. knowing how to walk, as the intellectual basis to understand a scientific domain, e.g. engineering and robot locomotion. Queens, backpacks, Remix and Robo add various abstractions to the system, and extend the tangible interface. Children use Topobo to transition from hands-on knowledge to theories that can be tested and reformulated, employing a combination of enactive, iconic and symbolic representations of ideas.by Hayes Solos Raffle.Ph.D

Towards naturalistic scanning environments for wearable magnetoencephalography

Magnetoencephalography (MEG) is a neuroimaging technique that probes human brain function, by measuring the magnetic fields generated at the scalp by current flow in assemblies of neurons. A direct measure of neural activity, MEG offers high spatiotemporal resolution, but limitations imposed by superconducting sensor technologies impede its clinical utility. Specifically, neuromagnetic fields are up to a billion times smaller than that of the Earth, meaning MEG must be performed inside a magnetically shielded room (MSR), which is typically expensive, heavy, and difficult to site. Furthermore, current MEG systems employ superconducting quantum interference devices (SQUIDs) to detect these tiny magnetic fields, however, these sensors require cryogenic cooling with liquid helium. Consequently, scanners are bulky, expensive, and the SQUIDs must be arranged in a fixed, one-size-fits-all array. Any movement relative to the fixed sensors impacts data quality, meaning participant movement in MEG is severely restricted. The development of technology to enable a wearable MEG system allowing free participant movement would generate a step change for the field. Optically-pumped magnetometers (OPMs) are an alternative magnetic field detector recently developed with sufficient sensitivity for MEG measurements. Operating at body temperature, in a small and lightweight sensor package, OPMs offer the potential for a wearable MEG scanner that allows participant movement, with sensors mounted on the scalp in a helmet or cap. However, OPMs operate around a zero-field resonance, resulting in a narrow dynamic range that may be easily exceeded by movement of the sensor within a background magnetic field. Enabling a full range of participant motion during an OPM-MEG scan therefore presents a significant challenge, requiring precise control of the background magnetic field. This thesis describes the development of techniques to better control the magnetic environment for OPM-MEG. This includes greater reduction of background magnetic fields over a fixed region to minimise motion artefacts and facilitate larger movements, and the application of novel, multi-coil active magnetic shielding systems to enable flexibility in participant positioning within the MSR. We outline a new approach to map background magnetic fields more accurately, reducing the remnant magnetic field to <300 pT and yielding a five-fold reduction in motion artefact, to allow detection of a visual steady-state evoked response during continuous head motion. Employing state-of-the-art, triaxial OPMs alongside this precision magnetic field control technique, we map motor function during a handwriting task involving naturalistic head movements and investigate the advantages of triaxial sensitivity for MEG data analysis. Using multi-coil active magnetic shielding, we map motor function consistently in the same participant when seated and standing, and demonstrate the first OPM-MEG hyperscanning experiments. Finally, we outline how the integration of a multi-coil system into the walls of a lightweight MSR, when coupled with field control over a larger volume, provides an open scanning environment. In sum, these developments represent a significant step towards realising the full potential of OPM-MEG as a wearable functional neuroimaging technology