26,362 research outputs found
A conjectural generating function for numbers of curves on surfaces
I give a conjectural generating function for the numbers of -nodal
curves in a linear system of dimension on an algebraic surface. It
reproduces the results of Vainsencher for the case and
Kleiman-Piene for the case . The numbers of curves are expressed
in terms of five universal power series, three of which I give explicitly as
quasimodular forms. This gives in particular the numbers of curves of arbitrary
genus on a K3 surface and an abelian surface in terms of quasimodular forms,
generalizing the formula of Yau-Zaslow for rational curves on K3 surfaces. The
coefficients of the other two power series can be determined by comparing with
the recursive formulas of Caporaso-Harris for the Severi degrees in . We
verify the conjecture for genus 2 curves on an abelian surface. We also discuss
a link of this problem with Hilbert schemes of points.Comment: amslatex 13 page
Drum Transcription via Classification of Bar-level Rhythmic Patterns
acceptedMatthias Mauch is supported by a Royal Academy of Engineering
Research Fellowshi
Copper cable theft: revisiting the price–theft hypothesis
Objectives: To test the commonly espoused but little examined hypothesis that fluctuations in the price of metal are associated with changes in the volume of metal theft. Specifically, we analyze the relationship between the price of copper and the number of police recorded 'live’ copper cable thefts from the British railway network (2006 to 2012)
CCS from industrial sources
The literature concerning the application of CCS to industry is reviewed. Costs are presented for different sectors including ``high purity'' (processes which inherently produce a high concentration of CO2), cement, iron and steel, refinery and biomass. The application of CCS to industry is a field which has had much less attention than its application to the electricity production sector. Costs range from less than 2011 100/tCO 2 . In the words of a synthesis report from the United Nations Industrial Development Organisation (UNIDO) ``This area has so far not been the focus of discussions and therefore much attention needs to be paid to the application of CCS to industrial sources if the full potential of CCS is to be unlocked''
Constrained dynamic control of traffic junctions
Excessive traffic in our urban environments has detrimental effects on our health, economy and standard of living. To mitigate this problem, an adaptive traffic lights signalling scheme is developed and tested in this paper. This scheme is based on a state space representation of traffic dynamics, controlled via a dynamic programme. To minimise implementation costs, only one loop detector is assumed at each link. The comparative advantages of the proposed system over optimal fixed time control are highlighted through an example. Results will demonstrate the flexibility of the system when applied to different junctions. Monte Carlo runs of the developed scheme highlight the consistency and repeatability of these results.peer-reviewe
Dust in active nuclei. I. Evidence for "anomalous" properties
We present observational evidences that dust in the circumnuclear region of
AGNs has different properties than in the Galactic diffuse interstellar medium.
By comparing the reddening of optical and infrared broad lines and the X-ray
absorbing column density we find that the E(B-V)/N_H ratio is nearly always
lower than Galactic by a factor ranging from ~3 up to ~100. Other observational
results indicate that the Av/N_H ratio is significantly lower than Galactic in
various classes of AGNs including intermediate type 1.8-1.9 Seyferts, hard
X-ray selected and radio selected quasars, broad absorption line QSOs and grism
selected QSOs. The lack of prominent absorption features at 9.7um (silicates)
and at 2175A (carbon dip) in the spectra of Seyfert 2s and of reddened Seyfert
1s, respectively, add further evidence for dust in the circumnuclear region of
AGNs being different from Galactic.
These observational results indicate that the dust composition in the
circumnuclear region of AGNs could be dominated by large grains, which make the
extinction curve flatter, featureless and are responsible for the reduction of
the E(B-V)/N_H and Av/N_H ratios.
Regardless of the physical origin of these phenomena, the reduced dust
absorption with respect to what expected from the gaseous column density should
warn about a mismatch between the optical and the X-ray classification of the
active galactic nuclei in terms of their obscuration.Comment: 9 pages, 3 figures, accepted for publication in A&
Magnetic properties of polypyrrole - coated iron oxide nanoparticles
Iron oxide nanoparticles were prepared by sol -gel process. Insitu
polymerization of pyrrole monomer in the presence of oxygen in iron oxide
ethanol suspension resulted in a iron oxide - polypyrrole nanocomposite. The
structure and magnetic properties were investigated for varying pyrrole
concentrations. The presence of the gamma - iron oxide phase and polypyrrole
were confirmed by XRD and FTIR respectively. Agglomeration was found to be
comparatively much reduced for the coated samples, as shown by TEM. AC
susceptibility measurements confirmed the superparamagnetic behaviour.
Numerical simulations performed for an interacting model system are performed
to estimate the anisotropy and compare favourably with experimental results.Comment: 11 pages,8 figure
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