The influence of radiation on the temperature profile of an induced discharge in argon at atmospheric pressure

This study presents a quantitative evaluation of the influence of radiation upon the parameters of a long induced discharge in argon at atmospheric pressure. Radiation heat transfer in the optically transparent tin plasma layers with thickness of the order of several centimeters) and reabsorption spectral intervals is examined. Experimental error produced by inaccurate knowledge of the transfer and optical characteristics of the plasma is evaluated. The effect of convection on radial temperature profile is evaluated.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiztki, No. 6, pp. 35–43, November–December, 1971.     

Méthodes d'approximation et d'itération pour les opérateurs monotones

Sans résumé Mémoire présenté par J. L. Lions     

Time-intensity transformation and internal stress in UV-curable hyperbranched acrylates

The photocuring of three different highly functional acrylates—Di-pentaerythritol penta/hexaacrylate (DPHA) and two hyperbranched molecules (HBP), one with a stiff polyester and one with a more flexible polyether structure—was investigated by means of photorheology, photo differential scanning calorimetry, and beam bending. Special attention was paid to the influence of the composition of DPHA/HBP reactive blends and UV intensity on gelation and vitrification and the resulting dynamics of the internal stress. It was found that adding HBPs to DPHA did not influence gelation significantly, but shifted the onset of vitrification to higher conversions and thus caused lower internal stresses in the material. Increasing UV intensity increased both the conversion at vitrification, thus retarding the build-up of internal stresses, and the ultimate conversion, thus increasing the final stress level. The obtained conversion, gelation, and vitrification data were assembled into time-intensity transformation diagrams, thus providing a useful tool for optimizing photocuring. This paper was presented at Annual European Rheology Conference (AERC) held in Hersonisos, Crete, Greece, April 27–29, 2006.     

Measurement of uniform and localized heat dissipation induced by cyclic loading

An experimental technique is presented for measuring the heat dissipation and localization during cyclic loading of materials. The temperature field is measured by a number of thermistors and an infrared camera, which scans the specimen surface continuously. The specimen is mounted inside an isothermal chamber. The measured whole-field temperature can be used for detection of damage propagation and localization. The resolution of the technique under various boundary conditions is discussed using a onedimensional model for the heat loss under steady-state conditions. Applications of the technique are demonstrated for specimens made of fiber-reinforced ceramic and polymer matrix composites (PMCs). A methodology is proposed for measuring changes in damping and stiffness properties of viscoelastic polymer matrix composites using the temperature rise of a cyclic loaded specimen. It is demonstrated that for a ceramic matrix composite, where interfacial frictional sliding gives rise to heat dissipation, the temperature resolution can be used for detection of stress-strain hysteresis with an accuracy better than that of the stress-strain data.     

On a New Route to Chaos in Railway Dynamics

Cooperrider's mathematical model of a railway bogie running on a straight track has been thoroughly investigated due to its interesting nonlinear dynamics (see True [1] for a survey). In this article a detailed numerical investigation is made of the dynamics in a speed range, where many solutions exist, but only a couple of which are stable. One of them is a chaotic attractor.Cooperrider's bogie model is described in Section 2, and in Section 3 we explain the method of numerical investigation. In Section 4 the results are shown. The main result is that the chaotic attractor is created through a period-doubling cascade of the secondary period in an asymptotically stable quasiperiodic oscillation at decreasing speed. Several quasiperiodic windows were found in the chaotic motion.This route to chaos was first described by Franceschini [9], who discovered it in a seven-mode truncation of the plane incompressible Navier–Stokes equations. The problem investigated by Franceschini is a smooth dynamical system in contrast to the dynamics of the Cooperrider truck model. The forcing in the Cooperrider model includes a component, which has the form of a very stiff linear spring with a dead band simulating an elastic impact. The dynamics of the Cooperrider truck is therefore non-smooth.The quasiperiodic oscillation is created in a supercritical Neimark bifurcation at higher speeds from an asymmetric unstable periodic oscillation, which gains stability in the bifurcation. The bifurcating quasiperiodic solution is initially unstable, but it gains stability in a saddle-node bifurcation when the branch turns back toward lower speeds.The chaotic attractor disappears abruptly in what is conjectured to be a blue sky catastrophe, when the speed decreases further.     

Using GPU parallelization to perform realistic simulations of the LPCTrap experiments

We performed classical molecular dynamics (MD) simulations in order to search the conditions for efficient sympathetic cooling of highly charged ions (HCIs) in a linear Paul trap. Small two-component ion Coulomb crystals consisting of laser-cooled ions and HCIs were characterized by the results of the MD simulations. We found that the spatial distribution is determined by not only the charge-to-mass ratio but also the space charge effect. Moreover, the simulation results suggest that the temperature of HCIs do not necessarily decrease with increasing the number of laser-cooled ions in the cases of linear ion crystals. We also determined the cooling limit of sympathetically cooled ¹⁶⁵Ho¹⁴⁺ ions in small linear ion Coulomb crystals. The present results show that sub-milli-Kelvin temperatures of at least 10 Ho¹⁴⁺ ions will be achieved by sympathetic cooling with a single laser-cooled Be⁺.     

Precision measurements with LPCTrap at GANIL

The experimental achievements and the results obtained so far with the LPCTrap device installed at GANIL are presented. The apparatus is dedicated to the study of the weak interaction at low energy by means of precise measurements of the β ? ν angular correlation parameter in nuclear β decays. So far, the data collected with three isotopes have enabled to determine, for the first time, the charge state distributions of the recoiling ions, induced by shakeoff process. The analysis is presently refined to deduce the correlation parameters, with the potential of improving both the constraint deduced at low energy on exotic tensor currents (⁶He¹⁺) and the precision on the V _{u d} element of the quark-mixing matrix (³⁵Ar¹⁺ and ¹⁹Ne¹⁺) deduced from the mirror transitions dataset.