Refocusing generalised normalisation

When defined with general elimination/application rules, natural deduction and $\lambda$-calculus become closer to sequent calculus. In order to get real isomorphism, normalisation has to be defined in a ``multiary'' variant, in which reduction rules are necessarily non-local (reason: nomalisation, like cut-elimination, acts at the \emph{head} of applicative terms, but natural deduction focuses at the \emph{tail} of such terms). Non-local rules are bad, for instance, for the mechanization of the system. A solution is to extend natural deduction even further to a \emph{unified calculus} based on the unification of cut and general elimination. In the unified calculus, a sequent term behaves like in the sequent calculus, whereas the reduction steps of a natural deduction term are interleaved with explicit steps for bringing heads to focus. A variant of the calculus has the symmetric role of improving sequent calculus in dealing with tail-active permutative conversions

When Microquasar Jets and Supernova Collide: Hydrodynamically Simulating the SS433-W50 Interaction

We present investigations of the interaction between the relativistic, precessing jets of the microquasar SS433 with the surrounding, expanding Supernova Remnant (SNR) shell W50, and the consequent evolution in the inhomogeneous Interstellar Medium (ISM). We model their evolution using the hydrodynamic FLASH code, which uses adaptive mesh refinement. We show that the peculiar morphology of the entire nebula can be reproduced to a good approximation, due to the combined effects of: (i) the evolution of the SNR shell from the free-expansion phase through the Sedov blast wave in an exponential density profile from the Milky Way disc, and (ii) the subsequent interaction of the relativistic, precessing jets of SS 433. Our simulations reveal: (1) Independent measurement of the Galaxy scale-height and density local to SS433 (as n_0 = 0.2 cm^{-3}, Z_d = 40 pc), with this scale-height being in excellent agreement with the work of Dehnen & Binney. (2) A new mechanism for hydrodynamic refocusing of conical jets. (3) The current jet precession characteristics do not simply extrapolate back to produce the lobes of W50 but a history of episodic jet activity having at least 3 different outbursts with different precession characteristics would be sufficient to produce the W50 nebula. A history of intermittent episodes of jet activity from SS433 is also suggested in a kinematic study of W50 detailed in a companion paper (Goodall et al, MNRAS submitted). (4) An estimate of the age of W50, and equivalently the age of SS433's black hole created during the supernova explosion, in the range of 17,000 - 21,000 years.Comment: Accepted to MNRAS for publication. 23 pages, 11 figures, 5 Tables. Website associated with manuscript: http://www-astro.physics.ox.ac.uk/~ptg/RESEARCH/research.htm

Are schools panoptic?

Schools are often understood by social researchers as panoptic spaces, where power is exercised through constant surveillance and monitoring. In this paper, I use Foucault’s notorious account of the Panopticon as a point of departure for a detailed empirical investigation of the specificities of surveillance in schools. Drawing on ethnographic data from fieldwork in a primary school, I argue that how surveillance actually operated in this context diverged from the panoptic programme in two crucial ways: surveillance was (i) discontinuous rather than total, and therefore open to resistance and evasion, and (ii) exercised through sound and hearing as much as through vision

Gaia in-orbit realignment. Overview and data analysis

The ESA Gaia spacecraft has two Shack-Hartmann wavefront sensors (WFS) on its focal plane. They are required to refocus the telescope in-orbit due to launch settings and gravity release. They require bright stars to provide good signal to noise patterns. The centroiding precision achievable poses a limit on the minimum stellar brightness required and, ultimately, on the observing time required to reconstruct the wavefront. Maximum likelihood algorithms have been developed at the Gaia SOC. They provide optimum performance according to the Cr\'amer-Rao lower bound. Detailed wavefront reconstruction procedures, dealing with partial telescope pupil sampling and partial microlens illumination have also been developed. In this work, a brief overview of the WFS and an in depth description of the centroiding and wavefront reconstruction algorithms is provided.Comment: 14 pages, 6 figures, 2 tables, proceedings of SPIE Astronomical Telescopes + Instrumentation 2012 Conference 8442 (1-6 July 2012

French mega-suppliers’ trajectories during the modular era: some evidences on Faurecia, Valeo and Plastic Omnium

The purpose of this paper is to present factual elements concerning the rise (decline) of French mega-suppliers. The study will focus on France’s three main mega-suppliers, all actors that have had a stake in carmakers’ modularisation strategies: Faurecia, Plastic Omnium and Valeo. Section 1 returns to the late 1980s and shows that the emergence of today’s mega-suppliers is rooted in this era and was piloted by French carmakers. Section 2 positions French mega-suppliers in a global hierarchy and distinguishes between two varieties: suppliers of simple parts; and module suppliers, with the latter constituting the focus for the rest of this text. Section 3 shows how module suppliers’ rise is rooted in their aggressive mergers and acquisitions (M&A) strategies. It also demonstrates differences between suppliers in terms of the two leading acquisition strategies that were observed. Section 4 explains why these companies’ profitability continues to disappoint, developing the idea that modular strategies imply a big rise in fixed costs, something that suppliers cannot knock onto sales prices. Finally, section 5 returns to companies’ internationalisation strategies and offers a typology for the different entities that mega-suppliers consolidatemodularity, supply chain, industrial architecture, automobile.

The standard plenoptic camera: applications of a geometrical light field model

A thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Doctor of PhilosophyThe plenoptic camera is an emerging technology in computer vision able to capture a light field image from a single exposure which allows a computational change of the perspective view just as the optical focus, known as refocusing. Until now there was no general method to pinpoint object planes that have been brought to focus or stereo baselines of perspective views posed by a plenoptic camera. Previous research has presented simplified ray models to prove the concept of refocusing and to enhance image and depth map qualities, but lacked promising distance estimates and an efficient refocusing hardware implementation. In this thesis, a pair of light rays is treated as a system of linear functions whose solution yields ray intersections indicating distances to refocused object planes or positions of virtual cameras that project perspective views. A refocusing image synthesis is derived from the proposed ray model and further developed to an array of switch-controlled semi-systolic FIR convolution filters. Their real-time performance is verified through simulation and implementation by means of an FPGA using VHDL programming. A series of experiments is carried out with different lenses and focus settings, where prediction results are compared with those of a real ray simulation tool and processed light field photographs for which a blur metric has been considered. Predictions accurately match measurements in light field photographs and signify deviations of less than 0.35 % in real ray simulation. A benchmark assessment of the proposed refocusing hardware implementation suggests a computation time speed-up of 99.91 % in comparison with a state-of-the-art technique. It is expected that this research supports in the prototyping stage of plenoptic cameras and microscopes as it helps specifying depth sampling planes, thus localising objects and provides a power-efficient refocusing hardware design for full-video applications as in broadcasting or motion picture arts