528 research outputs found
Crew interface definition study, phase 1
The timeline analysis of the Shuttle orbiter missions which was conducted in the Phase I Crew Interface Definition Study and the requirements for the man-in-the-loop simulation study are presented. Mission definitions and objectives are presented as they relate to various Shuttle Orbiter missions. The requirements for crew participation and the information required by the crew are discussed, and finally the rationale behind the display concept and calling procedures is given. The simulation objectives, the simulation mechanization, including a detailed presentation of the display and control concept, the simulator test plan and the results are discussed
Topological susceptibility from the overlap
The chiral symmetry at finite lattice spacing of Ginsparg-Wilson fermionic
actions constrains the renormalization of the lattice operators; in particular,
the topological susceptibility does not require any renormalization, when using
a fermionic estimator to define the topological charge. Therefore, the overlap
formalism appears as an appealing candidate to study the continuum limit of the
topological susceptibility while keeping the systematic errors under
theoretical control. We present results for the SU(3) pure gauge theory using
the index of the overlap Dirac operator to study the topology of the gauge
configurations. The topological charge is obtained from the zero modes of the
overlap and using a new algorithm for the spectral flow analysis. A detailed
comparison with cooling techniques is presented. Particular care is taken in
assessing the systematic errors. Relatively high statistics (500 to 1000
independent configurations) yield an extrapolated continuum limit with errors
that are comparable with other methods. Our current value from the overlap is
\chi^{1/4} = 188 \pm 12 \pm 5 \MeV.Comment: 18 pages, 7 figure
Effective Hamiltonian Approach to Hyperon Beta Decay with Final-State Baryon Polarization
Using an effective Hamiltonian approach, we obtain expressions for hyperon
beta decay final-state baryon polarization. Terms through second order in the
energy release are retained. The resulting approximate expressions are much
simpler and more compact than the exact expressions, and they agree closely
with them.Comment: 1 Figure Will appear in Phys Rev D 60 Article 117505 (Dec 1, 1999
Cooling and the SU(2) Instanton Vaccuum
We present results of an investigation into the nature of instantons in
4-dimensional pure gauge lattice \ obtained from configurations which
have been cooled using an under-relaxed cooling algorithm. We discuss ways of
calibrating the cooling and the effects of different degrees of cooling, and
compare our data for the shapes, sizes and locations of instantons with
continuum results. In this paper we extend the ideas and techniques developed
by us for use in , and compare the results with those obtained by other
groups.Comment: 22 pages, LaTeX, uuencoded compressed tarfile of figures sent
separately. Full (compressed) postscript version (118k)available from
ftp://rock.helsinki.fi/pub/preprints/tft/Year1995/HU-TFT-95-21/paper.ps.
Deep Learning for Instrumented Ultrasonic Tracking: From synthetic training data to in vivo application
Instrumented ultrasonic tracking is used to improve needle localisation during ultrasound guidance of minimally-invasive percutaneous procedures. Here, it is implemented with transmitted ultrasound pulses from a clinical ultrasound imaging probe that are detected by a fibre-optic hydrophone integrated into a needle. The detected transmissions are then reconstructed to form the tracking image. Two challenges are considered with the current implementation of ultrasonic tracking. First, tracking transmissions are interleaved with the acquisition of B-mode images and thus, the effective B-mode frame rate is reduced. Second, it is challenging to achieve an accurate localisation of the needle tip when the signal-to-noise ratio is low. To address these challenges, we present a framework based on a convolutional neural network (CNN) to maintain spatial resolution with fewer tracking transmissions and to enhance signal quality. A major component of the framework included the generation of realistic synthetic training data. The trained network was applied to unseen synthetic data and experimental in vivo tracking data. The performance of needle localisation was investigated when reconstruction was performed with fewer (up to eight-fold) tracking transmissions. CNN-based processing of conventional reconstructions showed that the axial and lateral spatial resolution could be improved even with an eight-fold reduction in tracking transmissions. The framework presented in this study will significantly improve the performance of ultrasonic tracking, leading to faster image acquisition rates and increased localisation accuracy
Model of Inhomogeneous Impurity Distribution in Fermi Superfluids
The standard treatment of impurities in metals assumes a homogeneous
distribution of impurities. In this paper we study distributions that are
inhomogeneous. We discuss in detail the "isotropic inhomogeneous scattering
model" which takes into account the spatially varying scattering on the scale
of the superfluid coherence length. On a large scale the model reduces to a
homogeneous medium with renormalized parameter values. We apply the model to
superfluid 3He, where porous aerogel acts as the impurity. We calculate the
transition temperature Tc, the order parameter, and the superfluid density.
Both A- and B-like phases are considered. Two different types of behavior are
identified for the temperature dependence of the order parameter. We compare
the calculations with experiments on 3He in aerogel. We find that most of the
differences between experiments and the homogeneous theory can be explained by
the inhomogeneous model. All our calculations are based on the quasiclassical
theory of Fermi liquids. The parameters of this theory for superfluid 3He in
aerogel are discussed.Comment: 14 pages, 9 figures, minor change
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