Engineering topics
Gray, A.
Publications and source records attributed to Gray, A..
Large Colloids in Cholesteric Liquid Crystals
We describe a coarse-grained Landau-de Gennes model of liquid crystals (LCs) including hydrodynamics based on the Beris–Edwards equations. The model is employed to study the impact of large colloids on the long range LC defect structure in the cholesteric LC blue phases. ‘Large’ here means that the particle size is comparable to the cholesteric pitch, the length scale on which the LC order undergoes a helical twist. We investigate the case of a single particle, with either normal or degenerate planar anchoring, placed initially in an equilibrium blue phase LC. It is found that in some cases, well defined steady disclination structure emerges at the particle surface, while in other cases no clear steady state is reached in the simulations, and disclination reorganisation appears to proliferate through the bulk LC. These systems are of potential interest in the context of using LCs to template self-assembly of colloid structure, e.g., for opto-electronic devices. Computationally, we demonstrate a parallel approach using mixed message-passing and threaded model on graphical processing units allows effective and efficient progress for this problem.
New Science Opportunities Enabled by LCLS-II X-Ray Lasers
This document attempts to capture the most compelling new science opportunities that are enabled by the unique capabilities of the new LCLS-II X-ray laser facility, namely: soft and tender X-rays (0.25 to 5 keV) at high repetition rates (up to 1 MHz) and hard X-rays (up to 25 keV) at 120 Hz. Many compelling areas of science have been identified by the scientific community, through a series of workshops over the past several years, where LCLS-II offers the potential to significantly advance our understanding. This document is not intended to be comprehensive of all the science to be pursued at the future LCLS facility. In particular, it does not capture important ongoing science that will continue to exploit the existing capabilities of the present LCLS facility. Nevertheless, this document will help to establish a scientific foundation for the new facility (encompassing present LCLS capabilities and new LCLS-II capabilities), and will inform LCLS strategic planning and investments over the next 5-10 years. The emphasis of this document is on identifying broad scientific opportunities, elucidating their potential impact, and providing a first-order link between these opportunities and LCLS-II capabilities. Brief descriptions are provided for various experimental approaches to be used, and novel new approaches to be developed, along with select examples of required optics and instruments. However, this document is not intended to capture all the optics and instrumentation requirements. Similarly it does not provide a detailed plan for instrumentation design or for any associated research and development that might be required. Balancing the scientific opportunities and impact, with instrumentation needs, available resources, and infrastructure, will be part of the LCLS planning process which this document will help to inform.
Regional heritability advanced complex trait analysis for GPU and traditional parallel architectures
Motivation: Quantification of the contribution of genetic variation to phenotypic variation for complex traits becomes increasingly computationally demanding with increasing numbers of single-nucleotide polymorphisms and individuals. To meet the challenges in making feasible large-scale studies, we present the REgional heritability advanced complex trait analysis software. Adapted from advanced complex trait analysis (and, in turn, genome-wide complex trait analysis), it is tailored to exploit the parallelism present in modern traditional and graphics processing unit (GPU)-accelerated machines, from workstations to supercomputers. Results: We adapt the genetic relationship matrix estimation algorithm to remove limitations on memory, allowing the analysis of large datasets. Further, we build on this to develop a version of the code able to efficiently exploit GPU-accelerated systems for both the genetic relationship matrix and REstricted maximum likelihood (REML) parts of the analysis, offering substantial speedup over the traditional central processing unit version. We develop the ability to analyze multiple small regions of the genome across multiple compute nodes in parallel, following the ‘regional heritability’ approach. We demonstrate the new software using 1024 GPUs in parallel on one of the world’s fastest supercomputers. Availability: The code is freely available at http://www.epcc.ed.ac.uk/software-products
High-Temperature, High-Efficiency Solar Thermoelectric Generator Prototype
Abstract not provided
High-Temperature Receiver Designs for Supercritical CO2 Closed-Loop Brayton Cycles
Abstract not provided
Hard X-Ray Delay line for X-Ray Photon Correlation Spectroscopy and Jitter-Free Pump-Probe Experiments at LCLS
Abstract not provided
Astro-E2 Magnesium Diboride High Current Leads
The recent discovery of superconducting properties in MgB_2 and rapid development of small diameter steel-clad wires has opened up the possibility of enhancing the design of the baseline Astro-E2 high current lead assembly. Replacing YBCO filaments with MgB_2 wires and modifying the heat sink location can give much higher margins against quench from temperature oscillations of the 4 K heat sink, although wih some overall thermal penalty. The design and performance of a new lead assembly during flight qualification is discussed, with emphasis on thermal, structural, and electrical test results.
Prototyping and FPGA-based MAP synchronizer for very high rate FQPSK
While fundamental formulations of maximum a posteriori (MAP) estimation for symbol timing [1] have been in exisence for some time, it has generally not seen widespread usage in communications receivers due to its relatively greater complexity in comparison to other designs. However, MAP has been shown to provide significant performance advantages for the acquisition and tracking of digital modulations under low SNR conditions when compared to traditional techniques, such as the data transition tracking loop [2].
Adaptive routing in wireless communication networks using swarm intelligence
In this paper we focus on the network routing problem, and survey swarm intelligent approaches for its efficient solution, after a brief overview of power-aware routing schemes, which are important in the network examples outlined above.
Software reconfigurable processor technologies: the key to long-life infrastructure for future space missions
They present an overview of long-life reconfigurable processor technologies and of a specific architecture for implementing a software reconfigurable (software-defined) network processor for space applications.
The Pleodata Language and Representation
Pleodata (Pleomorphic Data) is a markup language developed and used by the MLS group.
Multi-Parent Clustering Algorithms from Stochastic Grammar Data Models
We introduce a statistical data model and an associated optimization-based clustering algorithm which allows data vectors to belong to zero, one or several parent clusters.
Flexible All-Digital Receiver for Bandwidth Efficient Modulations
An all-digital high data rate parallel receiver architecture developed jointly by Goddard Space Flight Center and the Jet Propulsion Laboratory is presented.
CCSDS - SFCG Efficient Modulation Methods Study at NASA/JPL - Phase 4: Interference Susceptibility
Susceptibility to two types of interfering signals was requested by the SFCG: a pure carrier (single frequency tone)and wide-band RFI (characteristics unspecified). Selecting a broad-band interfering signal is diffuclt because it should represent the types of interference to be found in the space science service bands.
An Integrated System for Multi-Rover Scientific Exploration
This paper describes an integrated system for coordinating multiple rover behavior with the overall goal of collecting planetary surface data.