13,584 research outputs found
Towards a Co-Evolutionary Model of Demographics and Infrastructure
National infrastructure systems provide a foundation for economic prosperity and well-being. In addition to factors
such as technological change and obsolescence, infrastructure systems need to respond to changing levels of
demand, which is strongly driven by population growth. However demographic change is not independent of
economic conditions, or the nature and quality of infrastructure. This research is concerned with the interrelationships
between demographics, economy and infrastructure.
The paper therefore develops a novel approach to modelling the evolution of a national economy in the context of
changing demographics and infrastructure provision. This approach is based in a model with coupled sub-systems
which are spatially disaggregate with explicit temporal dynamics. A version of the model is calibrated using a
demographic component which incorporates both natural change and migration, and an economic model which
recognises both labour and capital as factors of production. Infrastructure is present as an influence on accessibility,
geographical attractiveness and economic productivity.
The performance of the model is explored through a variety of scenarios which are offered as an initial proof of
concept of the feasibility of implementing a co-evolutionary model of demographic and economic growth over a
medium to long time horizon. These scenarios indicate the influence of government policies for international migration
and infrastructure investment on regional development and performance
Refining grain structure and porosity of an aluminium alloy with intensive melt shearing
The official published version of the article can be obtained at the link below.Intensive melt shearing was achieved using a twin-screw machine to condition an aluminium alloy prior to solidification. The results show that intensive melt shearing has a significant grain-refining effect. In addition, the intensive melt shearing reduces both the volume fraction and the size of porosity. It can reduce the density index from 10.50% to 2.87% and the average size of porosity in the samples solidified under partial vacuum from around 1 mm to 100 μm.Financial support was obtained from the EPSRC and the Technology Strategy Board
Landau parameters of nuclear matter in the spin and spin-isospin channels
The equation of state of spin and isospin polarized nuclear matter is
determined in the framework of the Brueckner theory including three-body
forces. The Landau parameters in the spin and spin-isospin sectors are derived
as a function of the baryonic density. The results are compared with the
Gamow-Teller collective modes. The relevance of and for neutron
stars is shortly discussed, including the magnetic susceptibility and the
neutron star cooling.Comment: 2 pages, 2 figures, RevTex4 forma
Su(3) Algebraic Structure of the Cuprate Superconductors Model based on the Analogy with Atomic Nuclei
A cuprate superconductor model based on the analogy with atomic nuclei was
shown by Iachello to have an structure. The mean-field approximation
Hamiltonian can be written as a linear function of the generators of
algebra. Using algebraic method, we derive the eigenvalues of the reduced
Hamiltonian beyond the subalgebras and of
algebra. In particular, by considering the coherence between s- and d-wave
pairs as perturbation, the effects of coherent term upon the energy spectrum
are investigated
Lamellar phase separation and dynamic competition in La0.23Ca0.77MnO3
We report the coexistence of lamellar charge-ordered (CO) and
charge-disordered (CD) domains, and their dynamical behavior, in
La0.23Ca0.77MnO3. Using high resolution transmission electron microscopy (TEM),
we show that below Tcd~170K a CD-monoclinic phase forms within the established
CO-orthorhombic matrix. The CD phase has a sheet-like morphology, perpendicular
to the q vector of the CO superlattice (a axis of the Pnma structure). For
temperatures between 64K and 130K, both the TEM and resistivity experiments
show a dynamic competition between the two phases: at constant T, the CD phase
slowly advances over the CO one. This slow dynamics appears to be linked to the
magnetic transitions occurring in this compound, suggesting important
magnetoelastic effects.Comment: 4 pages, 4 figure
Affine equivariant rank-weighted L-estimation of multivariate location
In the multivariate one-sample location model, we propose a class of flexible
robust, affine-equivariant L-estimators of location, for distributions invoking
affine-invariance of Mahalanobis distances of individual observations. An
involved iteration process for their computation is numerically illustrated.Comment: 16 pages, 4 figures, 6 table
Correlation effects in the ground state charge density of Mott-insulating NiO: a comparison of ab-initio calculations and high-energy electron diffraction measurements
Accurate high-energy electron diffraction measurements of structure factors
of NiO have been carried out to investigate how strong correlations in the Ni
3d shell affect electron charge density in the interior area of nickel ions and
whether the new ab-initio approaches to the electronic structure of strongly
correlated metal oxides are in accord with experimental observations. The
generalized gradient approximation (GGA) and the local spin density
approximation corrected by the Hubbard U term (LSDA+U) are found to provide the
closest match to experimental measurements. The comparison of calculated and
observed electron charge densities shows that correlations in the Ni 3d shell
suppress covalent bonding between the oxygen and nickel sublattices.Comment: 6 pages, LaTeX and 5 figures in the postscript forma
Induced Growth of Asymmetric Nanocantilever Arrays on Polar Surfaces
©2003 The American Physical Society. The electronic version of this article is the complete one and can be found online at: http://link.aps.org/doi/10.1103/PhysRevLett.91.185502DOI: 10.1103/PhysRevLett.91.185502We report that the Zn-terminated ZnO (0001) polar surface is chemically active and the oxygenterminated (0001) polar surface is inert in the growth of nanocantilever arrays. Longer and wider "comblike" nanocantilever arrays are grown from the (0001)-Zn surface, which is suggested to be a self-catalyzed process due to the enrichment of Zn at the growth front. The chemically inactive
(0001)-O surface typically does not initiate any growth, but controlling experimental conditions could lead to the growth of shorter and narrower nanocantilevers from the intersections between (0001)-O with (0110) surfaces
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