20,679 research outputs found
UKC ANSAware Survival Guide (for Modula-3)
The ANSAware platform is a suite of libraries and tools which facilitate the building of distributed applications. The documentation with the release forms little more that a reference manual to the language and does not aid the first time user. This document provides a simple introduction to distributed systems concepts and, through the use of an example, demonstrates how to build applications with ANSAware
Nonlinear magneto-optical rotation with frequency-modulated light in the geophysical field range
Recent work investigating resonant nonlinear magneto-optical rotation (NMOR)
related to long-lived (\tau\ts{rel} \sim 1 {\rm s}) ground-state atomic
coherences has demonstrated potential magnetometric sensitivities exceeding
for small () magnetic
fields. In the present work, NMOR using frequency-modulated light (FM NMOR) is
studied in the regime where the longitudinal magnetic field is in the
geophysical range (), of particular interest for many
applications. In this regime a splitting of the FM NMOR resonance due to the
nonlinear Zeeman effect is observed. At sufficiently high light intensities,
there is also a splitting of the FM NMOR resonances due to ac Stark shifts
induced by the optical field, as well as evidence of alignment-to-orientation
conversion type processes. The consequences of these effects for FM-NMOR-based
atomic magnetometry in the geophysical field range are considered.Comment: 8 pages, 8 figure
Synthesizing Certified Code
Code certification is a lightweight approach for formally demonstrating software quality. Its basic idea is to require code producers to provide formal proofs that their code satisfies certain quality properties. These proofs serve as certificates that can be checked independently. Since code certification uses the same underlying technology as program verification, it requires detailed annotations (e.g., loop invariants) to make the proofs possible. However, manually adding annotations to the code is time-consuming and error-prone. We address this problem by combining code certification with automatic program synthesis. Given a high-level specification, our approach simultaneously generates code and all annotations required to certify the generated code. We describe a certification extension of AutoBayes, a synthesis tool for automatically generating data analysis programs. Based on built-in domain knowledge, proof annotations are added and used to generate proof obligations that are discharged by the automated theorem prover E-SETHEO. We demonstrate our approach by certifying operator- and memory-safety on a data-classification program. For this program, our approach was faster and more precise than PolySpace, a commercial static analysis tool
Fermi-surface induced modulation in an optimally doped YBCO superconductor
We have observed a Fermi-surface (FS) induced lattice modulation in a YBCO
superconductor with a wavevector along CuO chains, {\it i.e.} =(0,,0). The value of is twice the Fermi
wavevector () along {\bf b*} connecting nearly nested FS `ridges'.
The modulation exists only within O-vacancy-ordered islands
(characterized by = and persists well above and
below . Our results are consistent with the presence of a FS-induced
charge-density wave
Effects of the standing accretion-shock instability and the lepton-emission self-sustained asymmetry in the neutrino emission of rotating supernovae
Rotation of core-collapse supernovae (SNe) affects the neutrino emission
characteristics. By comparing the neutrino properties of three
three-dimensional SN simulations of a 15 M_sun progenitor (one non-rotating
model and two models rotating at different velocities), we investigate how the
neutrino emission varies with the flow dynamics in the SN core depending on the
different degrees of rotation. The large-amplitude sinusoidal modulations due
to the standing accretion-shock instability (SASI) are weaker in both the
rotating models than in the non-rotating case. The SN progenitor rotation
reduces the radial velocities and radial component of the kinetic energy
associated with convection interior to the proto-neutron star. This effect
seems to disfavor the growth of the hemispheric neutrino-emission asymmetries
associated with the lepton-emission self-sustained asymmetry (LESA). An
investigation of the multipole expansion of the neutrino luminosity and the
electron neutrino lepton number flux shows a dominant quadrupolar mode in
rotating SN models. Our findings highlight the power of using neutrinos as
probes of SN hydrodynamics.Comment: 21 pages, including 17 figures. Characterization of LESA in rotating
models expanded; conclusions unchanged. Animated visualizations available at:
https://wwwmpa.mpa-garching.mpg.de/ccsnarchive/data/Walk2018
Recommended from our members
GPERF : a perfect hash function generator
gperf is a widely available perfect hash function generator written in C++. It automates a common system software operation: keyword recognition. gperf translates an n element user-specified keyword list keyfile into source code containing a k element lookup table and a pair of functions, phash and in_word_set. phash uniquely maps keywords in keyfile onto the range 0 .. k - 1, where k >/= n. If k = n, then phash is considered a minimal perfect hash function. in_word_set uses phash to determine whether a particular string of characters str occurs in the keyfile, using at most one string comparison.This paper describes the user-interface, options, features, algorithm design and implementation strategies incorporated in gperf. It also presents the results from an empirical comparison between gperf-generated recognizers and other popular techniques for reserved word lookup
Spin-stripe density varies linearly with hole content in single-layer Bi2201 cuprate
We have performed inelastic neutron scattering measurements on the
single-layer cuprate Bi2+xSr2-xCuO6+y (Bi2201) with x=0.2, 0.3, 0.4 and 0.5, a
doping range that spans the spin-glass (SG) to superconducting (SC) phase
boundary. The doping evolution of low energy spin fluctuations was found to be
characterized by a change of incommensurate modulation wave vector from the
tetragonal [110] to [100]/[010] directions, while maintaining a linear relation
between the incommensurability and the hole concentration, delta p. In the SC
regime, the spectral weight is strongly suppressed below 4 meV. Similarities
and differences in the spin correlations between Bi2201 and the prototypical
single-layer system La2-xSrxCuO4 are discussed.Comment: 5 page,4 figure
- …