1,352 research outputs found
The Rise and Fall of the Oslo School
In 1931 Ragnar Frisch became professor at the University of Oslo. By way of his research, a new study programme and new staff he created the ”Oslo School”, characterised by mathematical modelling, econometrics, economic planning and scepticism towards the market economy. Consequently, detailed state economic planning and governance dominated Norwegian economic policy for three decades after WWII. In the 1970s the School’s dominance came to an end when the belief in competitive markets gained a foothold and the economy had poor performance. As a result a decentralized market economy was reintroduced. However, mathematical modelling and econometrics remain in the core of most economic programmes.
Representations of world coordinates in FITS
The initial descriptions of the FITS format provided a simplified method for
describing the physical coordinate values of the image pixels, but deliberately
did not specify any of the detailed conventions required to convey the
complexities of actual image coordinates. Building on conventions in wide use
within astronomy, this paper proposes general extensions to the original
methods for describing the world coordinates of FITS data. In subsequent
papers, we apply these general conventions to the methods by which spherical
coordinates may be projected onto a two-dimensional plane and to
frequency/wavelength/velocity coordinates.Comment: 15 Pages, 1 figure, LaTex with Astronomy & Astrophysics macro
package, submitted to A&A, related papers at
http://www.aoc.nrao.edu/~egreise
Representations of celestial coordinates in FITS
In Paper I, Greisen & Calabretta (2002) describe a generalized method for
assigning physical coordinates to FITS image pixels. This paper implements this
method for all spherical map projections likely to be of interest in astronomy.
The new methods encompass existing informal FITS spherical coordinate
conventions and translations from them are described. Detailed examples of
header interpretation and construction are given.Comment: Consequent to Paper I: "Representations of world coordinates in
FITS". 45 pages, 38 figures, 13 tables, aa macros v5.2 (2002/Jun). Both
papers submitted to Astronomy & Astrophysics (2002/07/19). Replaced to try to
get figure and table placement right (no textual changes
Ferromagnetism in a hard-core boson model
The problem of ferromagnetism -- associated with a ground state with maximal
total spin -- is discussed in the framework of a hard-core model, which forbids
the occupancy at each site with more than one particle. It is shown that the
emergence of ferromagnetism on finite square lattices crucially depends on the
statistics of the particles. Fermions (electrons) lead to the well-known
instabilities for finite hole densities, whereas for bosons (with spin)
ferromagnetism appears to be stable for all hole densities.Comment: 8 pages, 7 figures, RevTex
The breakdown of the Nagaoka phase in the 2D t-J model
In the limit of weak exchange, J, at low hole concentration, the ground state
of the 2D t-J model is believed to be ferromagnetic. We study the leading
instability of this Nagaoka state, which emerges with increasing J. Both exact
diagonalization of small clusters, and a semiclassical analytical calculation
of larger systems show that above a certain critical value of the exchange,
Nagaoka's state is unstable to phase separation. In a finite-size system a
bubble of antiferromagnetic Mott insulator appears in the ground state above
this threshold. The size of this bubble depends on the hole concentration and
scales as a power of the system size, N
Development of an expert data reduction assistant
We propose the development of an expert system tool for the management and reduction of complex data sets. The proposed work is an extension of a successful prototype system for the calibration of CCD images developed by Dr. Johnston in 1987. The reduction of complex multi-parameter data sets presents severe challenges to a scientist. Not only must a particular data analysis system be mastered, (e.g. IRAF/SDAS/MIDAS), large amounts of data can require many days of tedious work and supervision by the scientist for even the most straightforward reductions. The proposed Expert Data Reduction Assistant will help the scientist overcome these obstacles by developing a reduction plan based on the data at hand and producing a script for the reduction of the data in a target common language
Multilevel modelling of mechanical properties of textile composites: ITOOL Project
The paper presents an overview of the multi-level modelling of textile composites in the ITOOL project, focusing on the models of textile reinforcements, which serve as a basis for micromechanical models of textile composites on the unit cell level. The modelling is performed using finite element analysis (FEA) or approximate methods (method of inclusions), which provide local stiffness and damage information to FEA of composite part on the macro-level
Desempenho da cultura do milho após três anos da aplicação de pó de basalto ao solo, com e sem fertilização.
O objetivo desse trabalho foi avaliar o efeito de doses de pó de basalto sobre a produtividade de milho, três anos após sua aplicação ao solo, em sistema de plantio direto, combinadas com a presença ou ausência de fertilização química. Não houve efeito de doses de pó de basalto e da interação entre as doses e a adubação sobre a produtividade de milho cultivado após três anos da aplicação do pó de basalto, todavia, houve efeito apenas de adubação, sendo essa prática favorável ao rendimento da cultura
Atributos químicos de um Latossolo Vermelho Distrófico típico afetados pela aplicação de pó de basalto.
Resumo – O pó de basalto, como fertilizante de liberação lenta, tem apresentado uma série de benefícios ao solo, especialmente, na sua capacidade de fornecer nutrientes às plantas. O objetivo deste trabalho foi o de avaliar, em casa de vegetação, o efeito da aplicação de pó de basalto em alguns atributos químicos de um Latossolo Vermelho Distrófico típico, após 30, 60, 120 e 360 dias de incubação. Os tratamentos consistiram de doses de pó de basalto, com granulometria muito fina, cuja composição era: MgO = 4,83 %; K2O = 1,17 %; P2O5 = 0,2% e CaO = 9%. Foram utilizadas doses equivalentes a 0, 2, 4, 8 e 12 t ha-1. Utilizou-se delineamento completamente casualizado com quatro repetições. Os dados coletados foram submetidos à análise de variância e à análise de regressão polinomial. O pó de basalto com a granulometria testada apresenta dissolução em um prazo mínimo de 30 dias. Foi verificado que em ambiente sem dreno de nutrientes há diminuição dos teores de Ca e Mg trocáveis e do pH do solo e aumentos dos teores de Al e P, com a aplicação do pó de basalto
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