Results 1 - 10 of 15281
Results 1 - 10 of 15281. Search took: 0.033 seconds
|Sort by: date | relevance|
[en] In this Letter, the entanglement dynamics of two interacting qubits in a common bath and in two independent baths, at finite and zero temperature are investigated. Entanglement sudden death (ESD) and entanglement sudden birth (ESB) are observed when the two qubits are embedded in two independent baths at finite temperature. At zero temperature, the entanglement of the two qubits may evolve to a steady state with non-zero value when the two qubits are embedded in a common bath, the entanglement sudden birth does not occur when the qubits are embedded in two independent baths.
[en] A system can be driven to nonequilibrium behavior in the presence of thermodynamic imbalances in its environment, such as temperature or chemical potential differences. In derivations of far-from-equilibrium fluctuation theorems, such imbalances are typically modeled as fixed, externally imposed thermodynamic forces. Here, we argue that fluctuation theorems can instead be understood in terms of the equilibrium dynamics of a larger supersystem, containing both the system of interest and its thermal surroundings. To this end, we consider rare fluctuations that spontaneously produce imbalances in the surroundings. In the aftermath of such fluctuations, the system of interest transiently behaves as though it were in the presence of an externally applied thermodynamic force. By applying the principle of detailed balance to these rare events, we recover the fluctuation theorem in both its transient and steady-state formulations. (paper)
[en] The availability of a high quality Open Source CFD simulation platform like OpenFOAM offers new R and D opportunities by providing direct access to models and solver implementation details. Efforts have been made by Hydro-Quebec to adapt OpenFOAM to hydroturbines for the development of steady-state capabilities. The paper describes the developments that have been made to implement new turbomachinery related capabilities: Multiple Frame of Reference solver, domain coupling interfaces (GGI, cyclicGGI and mixing plane) and specialized boundary conditions. Practical use of the new turbomachinery capabilities are demonstrated for the analysis of a 195-MW Francis hydroturbine.
[en] Control and modelling of continuum robots are challenging tasks for robotic researchers. Most works on modelling are limited to piecewise constant curvature. In many cases they neglect to model the actuators or avoid a continuum approach. In particular, in the latter case this leads to a complex model hardly implemented. In this work, a geometrically exact steady-state model of a tendon-driven manipulator inspired by the octopus arm is presented. It takes a continuum approach, fast enough to be implemented in the control law, and includes a model of the actuation system. The model was experimentally validated and the results are reported. In conclusion, the model presented can be used as a tool for mechanical design of continuum tendon-driven manipulators, for planning control strategies or as internal model in an embedded system. (paper)
[en] In particle systems subject to a nonuniform drive, particle migration is observed from the driven to the non-driven region and vice-versa, depending on details of the hopping dynamics, leading to apparent violations of Fick’s law and of steady-state thermodynamics. We propose and discuss a very basic model in the framework of independent random walkers on a pair of rings, one of which features biased hopping rates, in which this phenomenon is observed and fully explained. (paper: classical statistical mechanics, equilibrium and non-equilibrium)
[en] A new concept of steady-state scenario for a tokamak reactor is presented, which provides a solution of principle to the well-known problem of alignment of self-generated and non-inductively driven currents in the presence of an internal transport barrier. An effective control parameter is identified as the driven current at the barrier location, and the existence of a threshold in this parameter is demonstrated. This concept is applied in simulations to obtain a steady-state scenario within the specifications of the International Thermonuclear Experimental Reactor.
[en] Full text of publication follows. The steady-state operation (SSO) of high-performance plasma in the Large Helical Device (LHD) has been progressed steadily by increased heating power of more than 1 MW using ICH and ECH. In the 2012 year campaign, plasma performance of steady state operation was improved to higher density and temperature of 1*1019 m-3 and 2.5 keV for during 20 min. Plasma is sustained by newly installed ICH antenna (HAS antenna which can control the launching parallel wave number) and also using new gyrotron tubes of 77 GHz frequency. The higher wave number operation with dipole phasing of HAS antenna can sustain the higher density plasma steadily in comparison with monopole phasing operation. Typical plasma parameters of long pulse operation of around 20 minutes have been obtained. Bulk ions are helium and minority ion of ICRF heating mode is hydrogen. ECH of 77 GHz frequency is located at plasma center. The radial profiles of electron temperature and density of similar SSO plasma have also been obtained. SSO plasmas are terminated by various reasons. Major reason is arcing occurred inside the ICRF antennas. Local hot spots and erosions of divertor carbon plates are also observed. Particle and heat balances, behaviors of dust and flakes which also frequently terminate the steady state operations are studied and will be presented at the meeting. (authors)
[en] We investigate the possibility of chaining qubits by letting pairs of nearest-neighbor qubits dissipate into common environments. We then study entanglement dynamics within the chain and show that steady-state entanglement can be achieved.
[en] Full text: Steady-State Superconducting Tokamak-1 (SST-1) has 16 toroidal field (TF) and 9 superconducting poloidal field (PF) coils rated for 10 kA DC. The TF coils are connected in series and operated in DC condition, whereas the PF coils are operated independently in pulse mode. The SST-1 current feeder system (CFS) houses nine pairs of PF superconducting current leads and one pair of TF superconducting current leads. The SST-1 CFS had observed arcing incidences during OT discharge in past SST-1 campaigns. Similar arcing incidences have also been observed in other tokamaks devices also like KSTAR, W7-X, and EAST. The conditions which led to the electrical arcing in SST-1 CFS, thereby resulting in severe damages to the PF current leads and helium hydraulic lines will be presented in this paper. As an important preventive measure to avoid such arcing at PF current leads during SST-1 operation, insulation strengthening processes of the PF current leads have been initiated to increase the voltage isolation capability of the PF current leads. In the view of same, development of an insulation scheme using combination of polyimide and GFRP along with DGEBA epoxy resin and its validation at lab scale has been carried out. It involves study of chemical kinetics of resin towards curing cycle, electrical and mechanical characterizations of insulation samples at room temperature as well as at LN2 temperature. A breakdown voltage of > 25 kV DC has been successfully achieved with ∼ 1.2 mm of insulation thickness at lab scale insulation samples. In order to validate the proposed insulation system under specified helium Paschen conditions, a lab scale setup considering SST-1 operational requirements has been developed. The operation, salient features of test setup and results will also be presented in this paper. The progressive development of insulation system and validation from prototype scale to half-dummy current lead scale and thereafter implementation on actual PF current leads will also be presented in this paper. (author)