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Instruction history management for high-performance microprocessors
textHistory-driven dynamic optimization is an important factor in improving
instruction throughput in future high-performance microprocessors. Historybased
techniques have the ability to improve instruction-level parallelism by
breaking program dependencies, eliminating long-latency microarchitecture
operations, and improving prioritization within the microarchitecture. However,
a combination of factors, such as wider issue widths, smaller transistors,
larger die area, and increasing clock frequency, has led to microprocessors that
are sensitive to both wire delays and energy consumption. In this environment,
the global structures and long-distance communications that characterize current
history data management are limiting instruction throughput.
This dissertation proposes the ScatterFlow Framework for Instruction
History Management. Execution history management tasks, such as history
data storage, access, distribution, collection, and modification, are partitioned
and dispersed throughout the instruction execution pipeline. History data
packets are then associated with active instructions and flow with the instructions
as they execute, encountering the history management tasks along the
way. Between dynamic instances of the instructions, the history data packets
reside in trace-based history storage that is synchronized with the instruction
trace cache. Compared to traditional history data management, this ScatterFlow
method improves instruction coverage, increases history data access
bandwidth, shortens communication distances, improves history data accuracy
in many cases, and decreases the effective history data access time.
A comparison of general history management effectiveness between the
ScatterFlow Framework and traditional hardware tables shows that the ScatterFlow
Framework provides superior history maturity and instruction coverage.
The unique properties that arise due to trace-based history storage and
partitioned history management are analyzed, and novel design enhancements
are presented to increase the usefulness of instruction history data within the
ScatterFlow Framework.
To demonstrate the potential of the proposed framework, specific dynamic
optimization techniques are implemented using the ScatterFlow Framework.
These illustrative examples combine the history capture advantages
with the access latency improvements while exhibiting desirable dynamic energy
consumption properties. Compared to a traditional table-based predictor,
performing ScatterFlow value prediction improves execution time and reduces
dynamic energy consumption. In other detailed examples, ScatterFlowenabled
cluster assignment demonstrates improved execution time over previous
cluster assignment schemes, and ScatterFlow instruction-level profiling
detects more useful execution traits than traditional fixed-size and infinite-size
hardware tables.Electrical and Computer Engineerin
Modelling the stochasticity of high-redshift halo bias
A very large dynamic range with simultaneous capture of both large- and
small-scales in the simulations of cosmic structures is required for correct
modelling of many cosmological phenomena, particularly at high redshift. This
is not always available, or when it is, it makes such simulations very
expensive. We present a novel sub-grid method for modelling low-mass
() haloes, which are
otherwise unresolved in large-volume cosmological simulations limited in
numerical resolution. In addition to the deterministic halo bias that captures
the average property, we model its stochasticity that is correlated in time. We
find that the instantaneous binned distribution of the number of haloes is well
approximated by a log-normal distribution, with overall amplitude modulated by
this "temporal correlation bias". The robustness of our new scheme is tested
against various statistical measures, and we find that temporally correlated
stochasticity generates mock halo data that is significantly more reliable than
that from temporally uncorrelated stochasticity. Our method can be applied for
simulating processes that depend on both the small- and large-scale structures,
especially for those that are sensitive to the evolution history of structure
formation such as the process of cosmic reionization. As a sample application,
we generate a mock distribution of medium-mass () haloes inside a 500 Mpc, grid simulation box. This
mock halo catalogue bears a reasonable statistical agreement with a halo
catalogue from numerically-resolved haloes in a smaller box, and therefore will
allow a very self-consistent sets of cosmic reionization simulations in a box
large enough to generate statistically reliable data
Vibration-based methods for structural and machinery fault diagnosis based on nonlinear dynamics tools
This study explains and demonstrates the utilisation of different nonlinear-dynamics-based procedures for the purposes of structural health monitoring as well as for monitoring of robot joints
The GALEX Extended Mission: Surveying UV Tracers of the Hidden Side of Galaxy Evolution
The Galaxy Evolution Explorer (GALEX) continues its surveys of the ultraviolet sky. GALEX surveys have supported the following galaxy evolution investigations: calibrating UV as a star formation rate tracer, using wide and deep surveys to measure star formation history, studying the evolution of dust extinction and metallicity, selecting and analyzing galaxies in transitory states, finding local analogs to Lyman Break Galaxies, probing and time-dating star formation in a wide variety of physical regimes. Our continuing mission is focussed on relating star formation history and galaxy evolution paths to the properties of dark matter halos and their assembly history, and on beginning to relate the evolution of galaxies to that of black holes and the intergalactic medium. GALEX has proven that the UV is an ideal band to find and map star formation in low mass, low density objects, and potentially in primordial gas. With future UV missions it may be possible to map emission from the intergalactic and circum-galactic medium, and make a definitive connection between galaxy evolution and the cooling, accretion, heating, and enrichment of gas in the cosmic web
Projected Constraints on Modified Gravity Cosmologies from 21 cm Intensity Mapping
We present projected constraints on modified gravity models from the
observational technique known as 21 cm intensity mapping, where cosmic
structure is detected without resolving individual galaxies. The resulting map
is sensitive to both BAO and weak lensing, two of the most powerful
cosmological probes. It is found that a 200 m x 200 m cylindrical telescope,
sensitive out to z=2.5, would be able to distinguish DGP from most dark energy
models, and constrain the Hu & Sawicki f(R) model to |f_{R0}| < 9*10^(-6) at
95% confidence. The latter constraint makes extensive use of the lensing
spectrum in the nonlinear regime. These results show that 21 cm intensity
mapping is not only sensitive to modifications of the standard model's
expansion history, but also to structure growth. This makes intensity mapping a
powerful and economical technique, achievable on much shorter time scales than
optical experiments that would probe the same era.Comment: 10 pages, 5 figures, 1 table. Added references and expanded
discussion. As resubmitted to Phys. Rev. D, in response to reviewer comment
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Binary hypothesis-based impact damage detection for composite material system embedded with fiber Bragg gratings
Tracing Galaxy Formation with Stellar Halos II: Relating Substructure in Phase- and Abundance-Space to Accretion Histories
This paper explores the mapping between the observable properties of a
stellar halo in phase- and abundance-space and the parent galaxy's accretion
history in terms of the characteristic epoch of accretion and mass and orbits
of progenitor objects. The study utilizes a suite of eleven stellar halo models
constructed within the context of a standard LCDM cosmology. The results
demonstrate that coordinate-space studies are sensitive to the recent (0-8
Gyears ago) merger histories of galaxies (this timescale corresponds to the
last few to tens of percent of mass accretion for a Milky-Way-type galaxy).
Specifically, the {\it frequency, sky coverage} and {\it fraction of stars} in
substructures in the stellar halo as a function of surface brightness are
indicators of the importance of recent merging and of the luminosity function
of infalling dwarfs. The {\it morphology} of features serves as a guide to the
orbital distribution of those dwarfs. Constraints on the earlier merger history
(> 8 Gyears ago) can be gleaned from the abundance patterns in halo stars:
within our models, dramatic differences in the dominant epoch of accretion or
luminosity function of progenitor objects leave clear signatures in the
[alpha/Fe] and [Fe/H] distributions of the stellar halo - halos dominated by
very early accretion have higher average [alpha/Fe], while those dominated by
high luminosity satellites have higher [Fe/H]. This intuition can be applied to
reconstruct much about the merger histories of nearby galaxies from current and
future data sets.Comment: 21 pages, 20 figures. To appear in the Astrophysical Journa
Influence of blade aerodynamic model on prediction of helicopter rotor aeroacoustic signatures
Brown’s vorticity transport model has been used to investigate how the local blade aerodynamic model influences the quality of the prediction of the high-frequency airloads associated with blade–vortex interactions, and thus the accuracy with which the acoustic signature of a helicopter rotor can be predicted. The vorticity transport model can accurately resolve the structure of the wake of the rotor and allows significant flexibility in the way that the blade loading can be represented. The Second Higher-Harmonic Control Aeroacoustics Rotor Test was initiated to provide experimental insight into the acoustic signature of a rotor in cases of strong blade–vortex interaction. Predictions of two models for the local blade aerodynamics are compared with the test data. A marked improvement in accuracy of the predicted high-frequency airloads and acoustic signature is obtained when a lifting-chord model for the blade aerodynamics is used instead of a lifting-line-type approach. Errors in the amplitude and phase of the acoustic peaks are reduced, and the quality of the prediction is affected to a lesser extent by the computational resolution of the wake, with the lifting-chord model producing the best representation of the distribution of sound pressure below the rotor
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