Research activities at the PALS research infrastructure

The Prague Asterix Laser System (PALS) Research Infrastructure (RI) in Prague, one of only four kJ-class laser facilities in EU, has been offering its beam time to European researchers for already 14 years, since 2004 in the framework of the LASERLAB-Europe consortium. Till June 2014, the PALS RI has provided 4313 experimental days for a total of 41 projects with 303 international users from 42 different research institutions. Its principal experimental facility is a terawatt sub-ns iodine laser (1315?nm) with an optional plasma-based zinc XUV laser (21.2?nm), and an auxiliary Ti:Sapphire fs laser (1?J, 70?fs) exploited for femtosecond plasma probing and experiments with synchronised femtosecond and sub-nanosecond laser pulses at mean laser intensities of up to 30?PW/cm². The lasers are equipped with several target facilities and rich sets of instruments for both active and passive plasma diagnostics. The PALS main research areas include development and applications of secondary laser sources of high-energy ions and both coherent and non-coherent high-intensity XUV radiation, laboratory astrophysical and inertial fusion-relevant studies. In this paper, the main results having been achieved at PALS in the framework of LASERLAB-EUROPE international access activities during the last four years are highlighted.     

Chromatographic impulse response technique with curve fitting to measure binary diffusion coefficients and retention factors using polymer-coated capillary columns

The theoretical basis of a Gaussian-like approximate solution was applied to a chromatographic impulse response technique with curve fitting for measuring binary diffusion coefficients and retention factors using a polymer-coated capillary column. The formulae were derived for evaluating both the accuracy of the approximate solution and the sensitivity of the parameters. The validity of the solution also was confirmed experimentally for pulse injection of phenol in acetone into supercritical carbon dioxide flowing at 313.15 K and 11.6-28.6 MPa. Potential sources for experimental errors of the method are discussed.     

On the general problem of stability for impulsive differential equations

Criteria for stability, asymptotical stability and instability of the nontrivial solutions of the impulsive system

     

Utilization of the BARC critical facility for ADS related experiments

The paper discusses the basic design of the critical facility, whose main purpose is the physics validation of AHWR. Apart from moderator level control, the facility will have shutdown systems based on shutoff rods and multiple ranges of neutron detection systems. In addition, it will have a flux mapping system based on 25 fission chambers, distributed in the core. We are planning to use this reactor for experiments with a suitable source to simulate an ADS system. Any desired sub-criticality can be achieved by adjusting the moderator level. Apart from perfecting our experimental techniques, in simple configurations, we intend to study the one-way coupled core in this facility. Preliminary calculations, employing a Monte Carlo code TRIPOLI, are presented.      

Dynamical behaviors of the brusselator system with impulsive input

Responses of dynamic system to pulse perturbations were investigated theoretically and experimentally. The model used in this paper has been proved dissipative by impulsive and dynamic theory. Complex phenomena such as limit cycles, periodic solutions, and chaos were numerically demonstrated.     

Stability analysis for neural networks with inverse Lipschitzian neuron activations and impulses

In this paper, a new concept called α-inverse Lipschitz function is introduced. Based on the topological degree theory and Lyapunov functional method, we investigate global convergence for a novel class of neural networks with impulses where the neuron activations belong to the class of α-inverse Lipschitz functions. Some sufficient conditions are derived which ensure the existence, and global exponential stability of the equilibrium point of neural networks. Furthermore, we give two results which are used to check the stability of uncertain neural networks. Finally, two numerical examples are given to demonstrate the effectiveness of results obtained in this paper.     

An acceleration of Erlenkotter-Körkel’s algorithms for the uncapacitated facility location problem

This contribution is focused on an acceleration of branch and bound algorithms for the uncapacitated facility location problem. Our approach is based on the well-known Erlenkotters’ procedures and Körkels’ multi-ascent and multi-adjustment algorithms, which have proved to be the efficient tools for solving the large-sized instances of the uncapacitated facility location problem. These two original approaches were examined and a thorough analysis of their performance revealed how each particular procedure contributes to the computational time of the whole algorithms. These analyses helped us to focus our effort on the most frequent procedures. The unique contribution of this paper is a new dual ascent procedure. This procedure leads to considerable acceleration of the lower bound computation process and reduces the resulting computational time. To demonstrate more efficient performance of amended algorithms we present the results of extensive numerical experiments.