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Leveraging legacy codes to distributed problem solving environments: A web service approach
This paper describes techniques used to leverage high performance legacy codes as CORBA components to a distributed problem solving environment. It first briefly introduces the software architecture adopted by the environment. Then it presents a CORBA oriented wrapper generator (COWG) which can be used to automatically wrap high performance legacy codes as CORBA components. Two legacy codes have been wrapped with COWG. One is an MPI-based molecular dynamic simulation (MDS) code, the other is a finite element based computational fluid dynamics (CFD) code for simulating incompressible Navier-Stokes flows. Performance comparisons between runs of the MDS CORBA component and the original MDS legacy code on a cluster of workstations and on a parallel computer are also presented. Wrapped as CORBA components, these legacy codes can be reused in a distributed computing environment. The first case shows that high performance can be maintained with the wrapped MDS component. The second case shows that a Web user can submit a task to the wrapped CFD component through a Web page without knowing the exact implementation of the component. In this way, a user’s desktop computing environment can be extended to a high performance computing environment using a cluster of workstations or a parallel computer
A spinor approach to Walker geometry
A four-dimensional Walker geometry is a four-dimensional manifold M with a
neutral metric g and a parallel distribution of totally null two-planes. This
distribution has a natural characterization as a projective spinor field
subject to a certain constraint. Spinors therefore provide a natural tool for
studying Walker geometry, which we exploit to draw together several themes in
recent explicit studies of Walker geometry and in other work of Dunajski (2002)
and Plebanski (1975) in which Walker geometry is implicit. In addition to
studying local Walker geometry, we address a global question raised by the use
of spinors.Comment: 41 pages. Typos which persisted into published version corrected,
notably at (2.15
Predicting Future Instance Segmentation by Forecasting Convolutional Features
Anticipating future events is an important prerequisite towards intelligent
behavior. Video forecasting has been studied as a proxy task towards this goal.
Recent work has shown that to predict semantic segmentation of future frames,
forecasting at the semantic level is more effective than forecasting RGB frames
and then segmenting these. In this paper we consider the more challenging
problem of future instance segmentation, which additionally segments out
individual objects. To deal with a varying number of output labels per image,
we develop a predictive model in the space of fixed-sized convolutional
features of the Mask R-CNN instance segmentation model. We apply the "detection
head'" of Mask R-CNN on the predicted features to produce the instance
segmentation of future frames. Experiments show that this approach
significantly improves over strong baselines based on optical flow and
repurposed instance segmentation architectures
An alternative roughness parameterization for soil moisture retrievals from passive microwave observations
Antiferromagnetism and hot spots in CeIn
Enormous mass enhancement at ''hot spots'' on the Fermi surface (FS) of
CeIn has been reported at strong magnetic field near its antiferromagnetic
(AFM) quantum critical point [T. Ebihara et al., Phys. Rev. Lett. 93, 246401
(2004)] and ascribed to anomalous spin fluctuations at these spots. The ''hot
spots'' lie at the positions on FS where in non-magnetic LaIn the narrow
necks are protruded. In paramagnetic phase CeIn has similar spectrum. We
show that in the presence of AFM ordering its FS undergoes a topological change
at the onset of AFM order that truncates the necks at the ''hot spots'' for one
of the branches. Applied field leads to the logarithmic divergence of the dHvA
effective mass when the electron trajectory passes near or through the neck
positions. This effect explains the observed dHvA mass enhancement at the ''hot
spots'' and leads to interesting predictions concerning the spin-dependence of
the effective electron mass. The (T,B)-phase diagram of CeIn, constructed
in terms of the Landau functional, is in agreement with experiment.Comment: 4 pages, 1 figur
Karyotype studies on grape phylloxera (Daktulosphaira vitifoliae FITCH)
A cytogenetic technique was developed to produce suitable chromosome spreads for phylloxera karyotype analysis. The karyotype for pathogenetic phylloxera was 2 n = 10. Karyotypes from haploid sex cells were found to vary between n = 5 and n = 6, the latter possibly indicating an aneuploidic aberration. Tetra- and polyploid cells were detected in somatic trophocytes. Preparation of phylloxera sex and somatic cells for chromosomal analysis reported here enables the study of genetic variation on a chromosomal scale
Paramagnetic Phase of a Heavy-Fermion Compound, CeFePO, Probed by 57Fe M\"{o}ssbauer Spectroscopy
57Fe M\"{o}ssbauer spectroscopy was applied to an iron-based layered compound
CeFePO. At temperatures from 9.4 to 293 K, no magnetic splitting was observed
in the M\"ossbauer spectra of CeFePO indicating a paramagnetic phase of the Fe
magnetic sublattice. All the spectra were fitted with a small quadrupole
splitting, and the Debye temperature of CeFePO was found to be \sim448 K. The
isomer shift at room temperature, 0.32 mm/s, was almost equal to those of
LnFeAsO (Ln = La, Ce, Sm). Comparing s-electron density using the isomer shifts
and unit cell volumes, it was found that the Fe of CeFePO has a similar valence
state to other layered iron-based quaternary oxypnictides except LaFePO
Pressure-induced unconventional superconductivity in the heavy-fermion antiferromagnet CeIn3: An 115In-NQR study under pressure
We report on the pressure-induced unconventional superconductivity in the
heavy-fermion antiferromagnet CeIn3 by means of nuclear-quadrupole-resonance
(NQR) studies conducted under a high pressure. The temperature and pressure
dependences of the NQR spectra have revealed a first-order quantum-phase
transition (QPT) from an AFM to PM at a critical pressure Pc=2.46 GPa. Despite
the lack of an AFM quantum critical point in the P-T phase diagram, we
highlight the fact that the unconventional SC occurs in both phases of the AFM
and PM. The nuclear spin-lattice relaxation rate 1/T1 in the AFM phase have
provided evidence for the uniformly coexisting AFM+SC phase. In the HF-PM phase
where AFM fluctuations are not developed, 1/T1 decreases without the coherence
peak just below Tc, followed by a power-law like T dependence that indicates an
unconventional SC with a line-node gap. Remarkably, Tc has a peak around Pc in
the HF-PM phase as well as in the AFM phase. In other words, an SC dome exists
with a maximum value of Tc = 230 mK around Pc, indicating that the origin of
the pressure-induced HF SC in CeIn3 is not relevant to AFM spin fluctuations
but to the emergence of the first-order QPT in CeIn3. When the AFM critical
temperature is suppressed at the termination point of the first-order QPT, Pc =
2.46 GPa, the diverging AFM spin-density fluctuations emerge at the critical
point from the AFM to PM. The results with CeIn3 leading to a new type of
quantum criticality deserve further theoretical investigations
Coarse-graining the dynamics of coupled oscillators
We present an equation-free computational approach to the study of the
coarse-grained dynamics of {\it finite} assemblies of {\it non-identical}
coupled oscillators at and near full synchronization. We use coarse-grained
observables which account for the (rapidly developing) correlations between
phase angles and oscillator natural frequencies. Exploiting short bursts of
appropriately initialized detailed simulations, we circumvent the derivation of
closures for the long-term dynamics of the assembly statistics.Comment: accepted for publication in Phys. Rev. Let
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