1,000 research outputs found
Manganese bismuth thin film for large capacity digital memories
Material and system research defines accurate memory characteristics in regard to write, read, erase and data operations of manganese bismuth materials
Influence of analysis and design models on minimum weight design
The results of numerical experiments designed to illustrate how the minimum weight design, accuracy, and cost can be influenced by: (1) refinement of the finite element analysis model and associated load path problems, and (2) refinement of the design variable linking model are examined. The numerical experiments range from simple structures where the modelling decisions are relatively obvious and less costly to the more complex structures where such decisions are less obvious and more costly. All numerical experiments used employ the dual formulation in ACCESS-3 computer program. Guidelines are suggested for creating analysis and design models that predict a minimum weight structure with greater accuracy and less cost. These guidelines can be useful in an interactive optimization environment and in the design of heuristic rules for the development of knowledge-based expert optimization systems
Low level of virological failure and drug resistance among patients receiving antiretroviral treatment under programme conditions in Maputo, Mozambique
Mexico AIDS Conference 200
Circular dielectric cavity and its deformations
The construction of perturbation series for slightly deformed dielectric
circular cavity is discussed in details. The obtained formulae are checked on
the example of cut disks. A good agreement is found with direct numerical
simulations and far-field experiments.Comment: 17 pages, 12 figure
Spectral properties of distance matrices
Distance matrices are matrices whose elements are the relative distances
between points located on a certain manifold. In all cases considered here all
their eigenvalues except one are non-positive. When the points are uncorrelated
and randomly distributed we investigate the average density of their
eigenvalues and the structure of their eigenfunctions. The spectrum exhibits
delocalized and strongly localized states which possess different power-law
average behaviour. The exponents depend only on the dimensionality of the
manifold.Comment: 31 pages, 9 figure
Biofilms on glacial surfaces: hotspots for biological activity
Glaciers are important constituents in the Earth’s hydrological and carbon cycles, with predicted warming leading to increases in glacial melt and the transport of nutrients to adjacent and downstream aquatic ecosystems. Microbial activity on glacial surfaces has been linked to the biological darkening of cryoconite particles, affecting albedo and increased melt. This phenomenon, however, has only been demonstrated for alpine glaciers and the Greenland Ice Sheet, excluding Antarctica. In this study, we show via confocal laser scanning microscopy that microbial communities on glacial surfaces in Antarctica persist in biofilms. Overall, ~35% of the cryoconite sediment surfaces were covered by biofilm. Nanoscale scale secondary ion mass spectrometry measured significant enrichment of 13C and 15N above background in both Bacteroidetes and filamentous cyanobacteria (i.e., Oscillatoria) when incubated in the presence of 13C–NaHCO3 and 15NH4. This transfer of newly synthesised organic compounds was dependent on the distance of heterotrophic Bacteroidetes from filamentous Oscillatoria. We conclude that the spatial organisation within these biofilms promotes efficient transfer and cycling of nutrients. Further, these results support the hypothesis that biofilm formation leads to the accumulation of organic matter on cryoconite minerals, which could influence the surface albedo of glaciers
Percolation model for nodal domains of chaotic wave functions
Nodal domains are regions where a function has definite sign. In recent paper
[nlin.CD/0109029] it is conjectured that the distribution of nodal domains for
quantum eigenfunctions of chaotic systems is universal. We propose a
percolation-like model for description of these nodal domains which permits to
calculate all interesting quantities analytically, agrees well with numerical
simulations, and due to the relation to percolation theory opens the way of
deeper understanding of the structure of chaotic wave functions.Comment: 4 pages, 6 figures, Late
Exploring the parameter space of MagLIF implosions using similarity scaling. III. Rise-time scaling
Magnetized Liner Inertial Fusion (MagLIF) is a z-pinch
magneto-inertial-fusion (MIF) concept studied on the Z Machine at Sandia
National Laboratories. Two important metrics characterizing current delivery to
a z-pinch load are the peak current and the current-rise time, which is roughly
the time interval to reach peak current. It is known that, when driving a
z-pinch load with a longer current-rise time, the performance of the z-pinch
decreases. However, a theory to understand and quantify this effect is still
lacking. In this paper, we utilize a framework based on similarity scaling to
analytically investigate the variations in performance of MagLIF loads when
varying the current-rise time, or equivalently, the implosion timescale. To
maintain similarity between the implosions, we provide the scaling
prescriptions of the experimental input parameters defining a MagLIF load and
derive the scaling laws for the stagnation conditions and for various
performance metrics. We compare predictions of the theory to 2D numerical
simulations using the radiation, magneto-hydrodynamic code HYDRA. For several
metrics, we find acceptable agreement between the theory and simulations. Our
results show that the voltage near the MagLIF load follows a weak scaling law
with respect to the
characteristic timescale of the voltage source, instead of the
ideal scaling. This occurs
because the imploding height of the MagLIF load must increase to preserve end
losses. As a consequence of the longer imploding liners, the required total
laser preheat energy and delivered electric energy increase. Overall, this
study may help understand the trade-offs of the MagLIF design space when
considering future pulsed-power generators with shorter and longer current-rise
times.Comment: 15 pages, 20 figures, submitted to Phys. Plasmas. arXiv admin note:
text overlap with arXiv:2209.1491
Trace formula for dielectric cavities II: Regular, pseudo-integrable, and chaotic examples
Dielectric resonators are open systems particularly interesting due to their
wide range of applications in optics and photonics. In a recent paper [PRE,
vol. 78, 056202 (2008)] the trace formula for both the smooth and the
oscillating parts of the resonance density was proposed and checked for the
circular cavity. The present paper deals with numerous shapes which would be
integrable (square, rectangle, and ellipse), pseudo-integrable (pentagon) and
chaotic (stadium), if the cavities were closed (billiard case). A good
agreement is found between the theoretical predictions, the numerical
simulations, and experiments based on organic micro-lasers.Comment: 18 pages, 32 figure
Inferring periodic orbits from spectra of simple shaped micro-lasers
Dielectric micro-cavities are widely used as laser resonators and
characterizations of their spectra are of interest for various applications. We
experimentally investigate micro-lasers of simple shapes (Fabry-Perot, square,
pentagon, and disk). Their lasing spectra consist mainly of almost equidistant
peaks and the distance between peaks reveals the length of a quantized periodic
orbit. To measure this length with a good precision, it is necessary to take
into account different sources of refractive index dispersion. Our experimental
and numerical results agree with the superscar model describing the formation
of long-lived states in polygonal cavities. The limitations of the
two-dimensional approximation are briefly discussed in connection with
micro-disks.Comment: 13 pages, 19 figures, accepted for publication in Physical Review
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