Algorithms to get a circulating beam

Two algorithms based of trajectory fitting have been used to obtain rapidly a circulating beam in LEP with strong focusing lattices. A new algorithm called "orbit closure" uses the beam positions measured at the first and the second turn. From their difference, it computes two corrector strengths per plane such that the second turn passes at the same place as the first turn at about ten BPM locations. This produces a closed orbit amplitude with an r.m.s. value close to that of the first turn trajectory. A new 'first turn threader' has been tried. It detects places where an oscillation with an r.m.s. amplitude larger than a specified value starts, and computes two corrector strengths to cancel it. By iterating this process, it should be possible to correct by steps the first turn trajectory so that its r.m.s amplitude is below a specified value. The orbit closure has been applied with success to a very low emittance lattice (135o in the horizontal plane) in LEP

Correction of the Systematic b3 Error with the Resonance-Free Lattice in the LHC

The effect of the sextupole component b3 in the LHC dipoles on the resonance-free lattice has been investigated. It is shown that its dynamic aperture, without b3 spool piece correction, is close to that of the nominal LHC lattice version 6.0 with spool pice correction. A prerequisite is the addition of a few chromaticity sextupoles in the dispersion suppressors. Under this condition an increase of the b3 component by a factor of two can probably be accepted. Furthermore, a systematic relative gradient error up to one per mil can be tolerated without changing this result

Sound and light from fractures in scintillators

Prompted by intriguing events observed in certain particle-physics searches for rare events, we study light and acoustic emission simultaneously in some inorganic scintillators subject to mechanical stress. We observe mechanoluminescence in ${Bi}_4{Ge}_{3}{O}_{12}$, ${CdWO}_{4}$ and ${ZnWO}_{4}$, in various mechanical configurations at room temperature and ambient pressure. We analyze how the light emission is correlated to acoustic emission during fracture. For ${Bi}_4{Ge}_{3}{O}_{12}$, we set a lower bound on the energy of the emitted light, and deduce that the fraction of elastic energy converted to light is at least $3 \times 10^{-5}$

Monte Carlo Calculations on Electron Backscattering in Amorphous or Polycrystalline Targets

We propose an application of the Monte Carlo method in the field of backscattering. The results obtained for incident electron energies ranging from 0.3 to 3 MeV and for targets of Al, Cu, Ag and Au are compared with experimental values from several sources. An electron travelling through matter undergoes successive collisions between which it is assumed to travel in a straight line. In our case, we consider the elementary process of interaction electron-nucleus; we have used analytical models for the scattering cross-sections. In order to follow the electron through the specimen, we divide the real trajectory into elements of length much smaller than the mean free path. Pseudo-random number process permits us to determine whether or not an interaction occurs, also the type of interaction. For the energy losses, we introduced a relation derived from Landau\u27s theory. We then followed the electron until it is emerged from the material or halted. The backscattering coefficients obtained for thin and thick targets as a function of the incident electron energy are in good agreement with the experimental data. We have introduced the depth distribution function of the backscattered electrons, which allows us to test the predictions of various theoretical models proposed by other authors

Measurement of Resonance Driving Terms from Turn-by-Turn Data

It has been shown that the Fourier analysis of recorded turn-by-turn tracking data can be used to derive resonance terms of an accelerator. Besides the resonance driving terms, the non-linear one-turn map can be obtained with all non-linearities arising from magnetic imperfections and correction elements. This could be interesting for the LHC which will be a machine that is dominated by strong non-linear fields. The methods works very well for tracking data and is expected to work equally well for turn-by-turn beam data. The precision to which these terms can be determined relies on the frequency analysis tool. To demonstrate the feasibility of the method, measurements of real accelerators are presented in which the beam is kicked once and the beam oscillations are recorded over several thousand turns. Besides the tune, the strengths of resonance driving terms have been measured and the results are compared with numerical calculation

Integrated architectures for computer vision : Automatic synthesis with three examples

Computer aided computer design is an open problem because computers are becoming more and more powerfull, more and more complex and .. smaller. We explain what "automatic (high-level) synthesis of integrated circuits" means . It is now feasible and necessary for computer vision dedicated architectures in particular. Since it requires an optimization within an ill-formalized and ill-defined design space, we describe the experimental method aiming at : 1) proving the existence of a solution for each application case, 2) finding and instanciating the optimization parameters - including the initial state -,3) effectively designing an integrated circuit and 4) redesigning the solutions for more complex architectures to still meet real-time constraints . The method is self-illustrated with three increasingly complex examples all along this paper.La construction automatique d'ordinateur assistée par ordinateur C(AO)2 est un problème ouvert parce que ceux-ci deviennent de plus en plus puissants, donc plus complexes et... plus petits. Nous expliquons ce qu'est la synthèse automatique de circuits intégrés dite de « haut niveau », technique désormais plausible et nécessaire notamment pour les architectures spécialisées en vision par ordinateur. S'agissant d'une optimisation dans un ensemble difficile à formaliser et à circonscrire nous décrivons la démarche expérimentale suivie afin de : 1) prouver l'existence d'une solution par cas d'application, 2) déterminer les paramètres de l'optimisation, dont l'état initial, et les instancier, 3) concevoir effectivement un circuit et 4) retraiter les solutions pour des architectures progressivement plus complexes n'en respectant pas moins des contraintes de temps réel. La démarche s'illustre par elle-même selon trois exemples de difficulté croissante qui jalonnent cet article

A conceptual map of invasion biology: Integrating hypotheses into a consensus network

Background and aims: Since its emergence in the mid-20th century, invasion biology has matured into a productive research field addressing questions of fundamental and applied importance. Not only has the number of empirical studies increased through time, but also has the number of competing, overlapping and, in some cases, contradictory hypotheses about biological invasions. To make these contradictions and redundancies explicit, and to gain insight into the field’s current theoretical structure, we developed and applied a Delphi approach to create a consensus network of 39 existing invasion hypotheses. Results: The resulting network was analysed with a link-clustering algorithm that revealed five concept clusters (resource availability, biotic interaction, propagule, trait and Darwin’s clusters) representing complementary areas in the theory of invasion biology. The network also displays hypotheses that link two or more clusters, called connecting hypotheses, which are important in determining network structure. The network indicates hypotheses that are logically linked either positively (77 connections of support) or negatively (that is, they contradict each other; 6 connections). Significance: The network visually synthesizes how invasion biology’s predominant hypotheses are conceptually related to each other, and thus, reveals an emergent structure – a conceptual map – that can serve as a navigation tool for scholars, practitioners and students, both inside and outside of the field of invasion biology, and guide the development of a more coherent foundation of theory. Additionally, the outlined approach can be more widely applied to create a conceptual map for the larger fields of ecology and biogeography.German Federal Ministry of Education and Research 01LC1501A-HDeutsche Forschungsgemeinschaft JE 288/9-2Czech Science Foundation 19-28807XCzech Academy of Sciences RVO 67985939Ministerio de Ciencia, Innovación y Universidades PCI2018- 092939, CGL-2014- 56739-RNatural Environmental Research Council NE/L002531/