3,137 research outputs found
Spatially Varying Steady State Longitudinal Magnetization in Distant Dipolar Field-based Sequences
Sequences based on the Distant Dipolar Field (DDF) have shown great promise
for novel spectroscopy and imaging. Unless spatial variation in the
longitudinal magnetization, M_{z}(s), is eliminated by relaxation, diffusion,
or spoiling techniques by the end of a single repetition, unexpected results
can be obtained due to spatial harmonics in the steady state M_{z}^{SS}(s)
profile. This is true even in a homogeneous single-component sample. We have
developed an analytical expression for the M_{z}^{SS}(s) profile that occurs in
DDF sequences when smearing by diffusion is negligible in the TR period. The
expression has been verified by directly imaging the M_{z}^{SS}(s) profile
after establishing the steady state. more keywords: magnetic resonance,
intermolecular multiple quantum coherence, mesoscale structure, iMQC, DDFComment: 7 pages, 4 figures, submitted to Journal of Magnetic Resonanc
Unaided stereo vision based pose estimation
This paper presents the development of a low-cost sensor platform for use in ground-based visual pose estimation and scene mapping tasks. We seek to develop a technical solution using low-cost vision hardware that allows us to accurately estimate robot position for SLAM tasks. We present results from the application of a vision based pose estimation technique to simultaneously determine camera poses and scene structure. The results are generated from a dataset gathered traversing a local road at the St Lucia Campus of the University of Queensland. We show the accuracy of the pose estimation over a 1.6km trajectory in relation to GPS ground truth
A first-principles study of oxygen vacancy pinning of domain walls in PbTiO3
We have investigated the interaction of oxygen vacancies and 180-degree
domain walls in tetragonal PbTiO3 using density-functional theory. Our
calculations indicate that the vacancies do have a lower formation energy in
the domain wall than in the bulk, thereby confirming the tendency of these
defects to migrate to, and pin, the domain walls. The pinning energies are
reported for each of the three possible orientations of the original Ti-O-Ti
bonds, and attempts to model the results with simple continuum models are
discussed.Comment: 8 pages, with 3 postscript figures embedded. Uses REVTEX and epsf
macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/lh_dw/index.htm
The role of grain boundary orientation and secondary phases in creep cavity nucleation of a 316h boiler header
Ekiden: A Platform for Confidentiality-Preserving, Trustworthy, and Performant Smart Contract Execution
Smart contracts are applications that execute on blockchains. Today they
manage billions of dollars in value and motivate visionary plans for pervasive
blockchain deployment. While smart contracts inherit the availability and other
security assurances of blockchains, however, they are impeded by blockchains'
lack of confidentiality and poor performance.
We present Ekiden, a system that addresses these critical gaps by combining
blockchains with Trusted Execution Environments (TEEs). Ekiden leverages a
novel architecture that separates consensus from execution, enabling efficient
TEE-backed confidentiality-preserving smart-contracts and high scalability. Our
prototype (with Tendermint as the consensus layer) achieves example performance
of 600x more throughput and 400x less latency at 1000x less cost than the
Ethereum mainnet.
Another contribution of this paper is that we systematically identify and
treat the pitfalls arising from harmonizing TEEs and blockchains. Treated
separately, both TEEs and blockchains provide powerful guarantees, but
hybridized, though, they engender new attacks. For example, in naive designs,
privacy in TEE-backed contracts can be jeopardized by forgery of blocks, a
seemingly unrelated attack vector. We believe the insights learned from Ekiden
will prove to be of broad importance in hybridized TEE-blockchain systems
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