Peculiarities of Ga and Te incorporation in glassy arsenic selenides

International audienceEffect of simultaneous Ga and Te addition on the structure of As2Se3 glasses is studied using X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) and Raman techniques. It is shown that most of As, Se and Te atoms build a covalent network according to their main valences. Three-fold coordinated As atoms form pyramidal structural units, which are connected via bridges of two-fold coordinated chalcogen atoms (Se, Te). On the other hand, coordination of Ga in glassy samples is found to be greater than three, as expected from its valence, increasing with Te content. Some of the As atoms appear to be converted into four-fold coordinated state at low Te concentration, while a fraction of Te and, possibly, Se atoms are thought to exist in a singly-coordinated (terminal) state in the vicinity of Ga in the samples with higher Te concentration

The LHC superconducting cavities

The LHC RF system, which must handle high intensity (0.5 A d.c.) beams, makes use of superconducting single-cell cavities, best suited to minimizing the effects of periodic transient beam loading. There will be eight cavities per beam, each capable of delivering 2 MV (5 MV/m accelerating field) at 400 MHz. The cavities themselves are now being manufactured by industry, using niobium-on-copper technology which gives full satisfaction at LEP. A cavity unit includes a helium tank (4.5 K operating temperature) built around a cavity cell, RF and HOM couplers and a mechanical tuner, all housed in a modular cryostat. Four-unit modules are ultimately foreseen for the LHC (two per beam), while at present a prototype version with two complete units is being extensively tested. In addition to a detailed description of the cavity and its ancillary equipment, the first test results of the prototype will be reported

Scenarios about the long-time damage of silicon as material and detectors operating beyond LHC collider conditions

For the new hadron collider LHC and some of its updates in luminosity and energy, as SLHC and VLHC, the silicon detectors could represent an important option, especially for the tracking system and calorimetry. The main goal of this paper is to analyse the expected long-time degradation in the bulk of the silicon as material and for silicon detectors, in continuous radiation field, in these hostile conditions. The behaviour of silicon in relation to various scenarios for upgrade in energy and luminosity is discussed in the frame a phenomenological model developed previously by the authors. Different silicon material parameters resulting from different technologies are considered to evaluate what materials are harder to radiation and consequently could minimise the degradation of device parameters in conditions of continuous long time operation.Comment: submitted to Physica Scripta Work in the frame of CERN RD-50 Collaboratio

Learning interpretable continuous-time models of latent stochastic dynamical systems

We develop an approach to learn an interpretable semi-parametric model of a latent continuoustime stochastic dynamical system, assuming noisy high-dimensional outputs sampled at uneven times. The dynamics are described by a nonlinear stochastic differential equation (SDE) driven by a Wiener process, with a drift evolution function drawn from a Gaussian process (GP) conditioned on a set of learnt fixed points and corresponding local Jacobian matrices. This form yields a flexible nonparametric model of the dynamics, with a representation corresponding directly to the interpretable portraits routinely employed in the study of nonlinear dynamical systems. The learning algorithm combines inference of continuous latent paths underlying observed data with a sparse variational description of the dynamical process. We demonstrate our approach on simulated data from different nonlinear dynamical systems

Report of the study group on a superconducting proton linac as a PS Injector

A proposal was made at the end of 1996 to use the large inventory of RF hardware available after the decommissioning of LEP-2 for the construction of a 2 GeV Superconducting Proton Linac (SPL) to inject directly into the PS [1.1]. The brightness of the beam in the PS at low energy would double, helping the injector complex to satisfy the requirements of the LHC and benefiting the planned proton physics programme. Additional users could also be accommodated thanks to the capability of the SPL to operate at a much larger duty factor than that required for high-energy physics. Consequently, a small study group has been set up to analyse the major technical aspects of the SPL design as well as the processes of injection and capture in the PS. This report summarises the work done so far, and provides some information about the other possible uses of the SPL beam. The feasibility of such a cascade of accelerators is confirmed, although an in-depth design study is still required before the realistic performance and detailed design of that facility can be announced

A flexible service selection for executing virtual services

[EN] With the adoption of a service-oriented paradigm on the Web, many software services are likely to fulfil similar functional needs for end-users. We propose to aggregate functionally equivalent software services within one single virtual service, that is, to associate a functionality, a graphical user interface (GUI), and a set of selection rules. When an end user invokes such a virtual service through its GUI to answer his/her functional need, the software service that best responds to the end-user s selection policy is selected and executed and the result is then rendered to the end-user through the GUI of the virtual service. A key innovation in this paper is the flexibility of our proposed service selection policy. First, each selection policy can refer to heterogeneous parameters (e.g., service price, end-user location, and QoS). Second, additional parameters can be added to an existing or new policy with little investment. Third, the end users themselves define a selection policy to apply during the selection process, thanks to the GUI element added as part of the virtual service design. This approach was validated though the design, implementation, and testing of an end-to-end architecture, including the implementation of several virtual services and utilizing several software services available today on the Web.This work was partially supported in part by SERVERY (Service Platform for Innovative Communication Environment), a CELTIC project that aims to create a Service Marketplace that bridges the Internet and Telco worlds by merging the flexibility and openness of the former with the trustworthiness and reliability of the latter, enabling effective and profitable cooperation among actors.Laga, N.; Bertin, E.; Crespi, N.; Bedini, I.; Molina Moreno, B.; Zhao, Z. (2013). A flexible service selection for executing virtual services. 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Methodological aspects of a mathematical programming model to evaluate soil tillage technologies in a risky environment

In this work we develop a methodology for the economic evaluation of soil tillage technologies, in a risky environment, and to capture the influence of farmer behaviour on his technology choice. The model has short-term activities, that change with the type of year, and long-term activities, in which sets of traction investment activities are included. Although these activities do not change with the type of year, they lead to different availability of resources for each type of year, since the same tractor has different available fieldwork days under different weather conditions. We prove that the model is sensitive to the greater income variability resulting from the use of alternative technologies and to the balance between income and risk, accounting for the probability of occurrence of each state of nature and giving an investment solution that considers the best production plan for each type of year. (c) 2005 Elsevier B.V. All rights reserved