Non-equilibrium two-phase coexistence in a confined granular layer

We report the observation of the homogenous nucleation of crystals in a dense layer of steel spheres confined between two horizontal plates vibrated vertically. Above a critical vibration amplitude, two-layer crystals with square symmetry were found to coexist in steady state with a surrounding granular liquid. By analogy to equilibrium hard sphere systems, the phase behavior can be explained through entropy maximization. However, dramatic non-equilibrium effects are present, including a significant difference in the granular temperatures of the two phases.Comment: 4 pages, 3 figures, RevTex4 forma

Crucial role of sidewalls in velocity distributions in quasi-2D granular gases

Our experiments and three-dimensional molecular dynamics simulations of particles confined to a vertical monolayer by closely spaced frictional walls (sidewalls) yield velocity distributions with non-Gaussian tails and a peak near zero velocity. Simulations with frictionless sidewalls are not peaked. Thus interactions between particles and their container are an important determinant of the shape of the distribution and should be considered when evaluating experiments on a tightly constrained monolayer of particles.Comment: 4 pages, 4 figures, Added reference, model explanation charified, other minor change

Finite-dimensional representations of twisted hyper loop algebras

We investigate the category of finite-dimensional representations of twisted hyper loop algebras, i.e., the hyperalgebras associated to twisted loop algebras over finite-dimensional simple Lie algebras. The main results are the classification of the irreducible modules, the definition of the universal highest-weight modules, called the Weyl modules, and, under a certain mild restriction on the characteristic of the ground field, a proof that the simple modules and the Weyl modules for the twisted hyper loop algebras are isomorphic to appropriate simple and Weyl modules for the non-twisted hyper loop algebras, respectively, via restriction of the action

Fusion of basic algorithms for detection and localization of vehicle plate numbers

Institut des Systèmes Intelligents et de Robotiqu

Construction of the probe beam photo-injector of CTF3

JACoW web site http://accelconf.web.cern.ch/AccelConf/e06This paper describes the HF (High-Frequency) and dynamic beam modelling performed onto the 3 GHz / 2,5 cells photo-injector of the future CTF3 (CLIC Test Facility 3) probe beam linac. The latter provides the beam to demonstrate the feasibility of the 30 GHz accelerating sections in the framework of the CLIC project. The Probe Beam Photo-Injector (PBPI) is inspired from the Drive Beam Photo-Injector (DBPI) already designed by LAL and actually tested in our laboratory. However, the design of PBPI has been simplified with respect to the previous because the charge per bunch is 4 times lower and the number of bunches several orders of magnitude smaller. The internal geometry and the coupling system of the PBPI have been designed with 2D (SUPERFISH*) and 3D (HFSS**) codes. Based on the modified design, PARMELA and POISSON simulations showed that the technical specifications are fulfilled. The vacuum issue has been also carefully investigated, and NEG (Non Evaporated Getter) technology has been adopted in order to reach the $10^–10$ mbar pressure inside the structure. This work is done in deep collaboration with CEA/Saclay, which is responsible of the CTF3 Probe Beam Linac design and construction [1]

Wilson ratio in Yb-substituted CeCoIn5

We have investigated the effect of Yb substitution on the Pauli limited, heavy fermion superconductor, CeCoIn$_5$. Yb acts as a non-magnetic divalent substituent for Ce throughout the entire doping range, equivalent to hole doping on the rare earth site. We found that the upper critical field in (Ce,Yb)CoIn$_5$ is Pauli limited, yet the reduced (H,T) phase diagram is insensitive to disorder, as expected in the purely orbitally limited case. We use the Pauli limiting field, the superconducting condensation energy and the electronic specific heat coefficient to determine the Wilson ratio ($R_{W}$), the ratio of the specific heat coefficient to the Pauli susceptibility in CeCoIn$_5$. The method is applicable to any Pauli limited superconductor in the clean limit.Comment: 5 pages, 1 table, 4 figure

Role of friction-induced torque in stick-slip motion

We present a minimal quasistatic 1D model describing the kinematics of the transition from static friction to stick-slip motion of a linear elastic block on a rigid plane. We show how the kinematics of both the precursors to frictional sliding and the periodic stick-slip motion are controlled by the amount of friction-induced torque at the interface. Our model provides a general framework to understand and relate a series of recent experimental observations, in particular the nucleation location of micro-slip instabilities and the build up of an asymmetric field of real contact area.Comment: 6 pages, 5 figure

PHIL: a Test Beam line at LAL

WEPP078International audienceIn the framework of a European contract*, LAL is in charge of the construction of one photo-injector for the drive beam linac of the CLIC Test Facility 3 [1] at CERN. This contract together with national funds allowed LAL to build a home test accelerator, PHIL, with the same photo-injector as for CTF3. The goal is to undergo experiments on the design and technology of advanced RF guns, to develop diagnostics and feedback techniques, a part of the beam time will be also shared with users of the electron beam. So far, the construction of this accelerator at LAL was very much delayed because of the legal obligation to upgrade the radiation shielding in agreement with the actual radiation safety thresholds. The required civil engineering is now finished and the installation of the components is under way. We will first present a design of the accelerator and few dynamic simulation results. Finally we will give an up to date status of the accelerator construction