1,097 research outputs found
H\"older Regularity of Geometric Subdivision Schemes
We present a framework for analyzing non-linear -valued
subdivision schemes which are geometric in the sense that they commute with
similarities in . It admits to establish
-regularity for arbitrary schemes of this type, and
-regularity for an important subset thereof, which includes all
real-valued schemes. Our results are constructive in the sense that they can be
verified explicitly for any scheme and any given set of initial data by a
universal procedure. This procedure can be executed automatically and
rigorously by a computer when using interval arithmetics.Comment: 31 pages, 1 figur
Monitoring infrastructure policy reforms and rural poverty reduction in Ghana : the case of Keta Sea Defence Project
Over the years Ghana has adopted many policy reforms with the aim of reducing poverty. Though official reports indicate reduction in poverty, poverty has become a rural phenomenon. An essential factor identified as crucial for rural poverty reduction is infrastructure. Though the government of Ghana has acknowledged the potential contribution of infrastructure to poverty reduction, and continues to increase annual expenditure on infrastructure provision, the government is worried about the failure of many infrastructure projects to reduce poverty. Since policies provide frameworks that guide action, it would be expected that Ghana’s infrastructure policies address these problems. The study explores the relationship between infrastructure and rural poverty reduction, and the adequacy of Ghana’s infrastructure policy environment in contributing to rural poverty reduction
Improved analysis of neutral pion electroproduction off deuterium in chiral perturbation theory
Near threshold neutral pion electroproduction on the deuteron is studied in
the framework of heavy baryon chiral perturbation theory. We include the
next-to-leading order corrections to the three-body contributions. We find an
improved description of the total and differential cross section data measured
at MAMI. We also obtain more precise values for the threshold S-wave
multipoles. We discuss in detail the theoretical uncertainties of the
calculation.Comment: 14 pp, 11 figs, uses svjour.cl
Cloud geometry from oxygen-A-band observations through an aircraft side window
During the ACRIDICON-CHUVA (Aerosol, Cloud, Precipitation,
and Radiation Interactions and Dynamics of Convective Cloud Systems–Cloud
Processes of the Main Precipitation Systems in Brazil: A Contribution to
Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement)) aircraft campaign in September 2014 over the
Amazon, among other topics, aerosol effects on the development of cloud
microphysical profiles during the burning season were studied. Hyperspectral
remote sensing with the imaging spectrometer specMACS provided cloud
microphysical information for sun-illuminated cloud sides. In order to derive
profiles of phase or effective radius from cloud side observations, vertical
location information is indispensable. For this purpose, spectral
measurements of cloud-side-reflected radiation in the oxygen A absorption
band collected by specMACS were used to determine absorption path length
between cloud sides and the instrument aboard the aircraft. From these data,
horizontal distance and eventually vertical height were derived.
It is shown that, depending on aircraft altitude and sensor viewing
direction, an unambiguous relationship of absorption and distance exists and
can be used to retrieve cloud geometrical parameters. A comparison to
distance and height information from stereo image analysis (using data of an
independent camera) demonstrates the efficiency of the approach. Uncertainty
estimates due to method, instrument and environmental factors are provided.
The main sources of uncertainty are unknown in cloud absorption path
contributions due to complex 3-D geometry or unknown microphysical
properties, variable surface albedo and aerosol distribution. A systematic
difference of 3.8 km between the stereo and spectral method is found which can
be attributed to 3-D geometry effects not considered in the method's
simplified cloud model. If this offset is considered, typical differences
found are 1.6 km for distance and 230 m for vertical position at a typical
distance around 20 km between sensor and convective cloud elements of
typically 1–10 km horizontal and vertical extent.</p
Evidence for a negative-parity spin-doublet of nucleon resonances at 1.88\,GeV
Evidence is reported for two nucleon resonances with spin-parity
and at a mass just below 1.9\,GeV. The evidence is derived from a
coupled-channel analysis of a large number of pion and photo-produced
reactions. The two resonances are nearly degenerate in mass with two resonances
of the same spin but positive parity. Such parity doublets are predicted in
models claiming restoration of chiral symmetry in high-mass excitations of the
nucleon. Further examples of spin parity doublets are found in addition.
Alternatively, the spin doublet can be interpreted as member of the 56-plet
expected in the third excitation band of the nucleon. Implications for the
problem of the {\it missing resonances} are discussed.Comment: 10 pages, 3 figures, 4 tables, minor revisio
Model Driven Software Development in the Context of Embedded Component Infrastructures
Epidemic space
The aim of this article is to highlight the importance of 'spatiality' in understanding the materialization of risk society and cultivation of risk sensibilities. More specifically it provides a cultural analysis of pathogen virulence (as a social phenomenon) by means of tracing and mapping the spatial flows that operate in the uncharted zones between the microphysics of infection and the macrophysics of epidemics. It will be argued that epidemic space consists of three types of forces: the vector, the index and the vortex. It will draw on Latour's Actor Network Theory to argue that epidemic space is geared towards instability when the vortex (of expanding associations and concerns) displaces the index (of finding a single cause)
A complex storm system in Saturn’s north polar atmosphere in 2018
Producción CientÃficaSaturn’s convective storms usually fall in two categories. One consists of mid-sized storms ∼2,000 km wide, appearing as irregular bright cloud systems that evolve rapidly, on scales of a few days. The other includes the Great White Spots, planetary-scale giant storms ten times larger than the mid-sized ones, which disturb a full latitude band, enduring several months, and have been observed only seven times since 1876. Here we report a new intermediate type, observed in 2018 in the north polar region. Four large storms with east–west lengths ∼4,000–8,000 km (the first one lasting longer than 200 days) formed sequentially in close latitudes, experiencing mutual encounters and leading to zonal disturbances affecting a full latitude band ∼8,000 km wide, during at least eight months. Dynamical simulations indicate that each storm required energies around ten times larger than mid-sized storms but ∼100 times smaller than those necessary for a Great White Spot. This event occurred at about the same latitude and season as the Great White Spot in 1960, in close correspondence with the cycle of approximately 60 years hypothesized for equatorial Great White Spots.Ministerio de EconomÃa, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project AYA2015-65041-P)Gobierno Vasco (project IT-366-19
Hamiltonian submanifolds of regular polytopes
We investigate polyhedral -manifolds as subcomplexes of the boundary
complex of a regular polytope. We call such a subcomplex {\it -Hamiltonian}
if it contains the full -skeleton of the polytope. Since the case of the
cube is well known and since the case of a simplex was also previously studied
(these are so-called {\it super-neighborly triangulations}) we focus on the
case of the cross polytope and the sporadic regular 4-polytopes. By our results
the existence of 1-Hamiltonian surfaces is now decided for all regular
polytopes.
Furthermore we investigate 2-Hamiltonian 4-manifolds in the -dimensional
cross polytope. These are the "regular cases" satisfying equality in Sparla's
inequality. In particular, we present a new example with 16 vertices which is
highly symmetric with an automorphism group of order 128. Topologically it is
homeomorphic to a connected sum of 7 copies of . By this
example all regular cases of vertices with or, equivalently, all
cases of regular -polytopes with are now decided.Comment: 26 pages, 4 figure
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