Artificial-intelligence-based interpretation of feature sensitivities of the Belousov-Zhabotinsky reaction

A new approach is presented for analyzing kinetic models of relaxation-type oscillatory systems on the basis of numerical data. Feature sensitivities of the length of the two kinetic states of the Belousov-Zhabotinsky (BZ) reaction with respect to the rate constants of the model are explained by means of a logic-based inference system. The main kinetic roles of the individual reaction steps on the relaxing components are revealed, and a consistent interpretation of the kinetic states is given by this process. Both the high and the low set of rate constants were studied. According to our analysis, the bromous acid-hypobromous acid reaction is an important Br^? producing step of the model, and in the case of the low set, the bromate-bromous acid reaction is not the rate-determining step of the bromous acid autocatalysis.     

Basic Mechanisms in Plasma Etching

A summary is given on the temperature dependence and basic processes in dry etching. The basic processes as Physical and Chemical Sputtering and Surface Film Etching completed by ion or electron stimulation of gas-surface reactions and combined with adsorption and desorption are used in modelling different types of etch characteristics. Of special interest are non-monotoneous characteristics. For some typical examples a comparison between measured and calculated curves is given which permit the determination of some kinetic parameters as activation energies and residence times.     

Experimental Study of Nonlinear Behaviour of a Neon Glow Discharge

We report on experimental investigations of a periodically perturbed Neon glow discharge in a parameter range where the unperturbed system is characterized by the existence of p- and r- waves. Though the experimental plasma system has many potential degrees of freedom, its phase space behaviour is low dimensional. The discharge current exhibits sequences of periodic, quasi-periodic and chaotic states which in many aspects correspond to a dissipative circle map. Moreover experiments show that the system displays a route to chaos via formation of entrainment islands and subsequent folding and break up of the tori, which cannot be described by a one-dimensional theory, and which has not been reported in the literature until now.     

Sensitivity analysis of the two kinetic states of the Belousov-Zhabotinsky reaction

A recently published kinetic model of the Belousov-Zhabotinsky reaction was studied by the feature sensitivity analysis of the slow bromide consumption and slow bromide production periods of the relaxing-type oscillatory system. The computed sensitivities allowed us to reveal the kinetic importance of the 17 individual reactions during the two, “kinetically homogeneous” states of the oscillation. Similarities and differences in the relative kinetic importances of the reaction steps were carefully studied when changing the magnitude of the rate constants (high set and low set). Of the 17 reactions examined, the attack of Ce⁴⁺ on malonic acid proved to be an essential step of the mechanism. Using the low set, there emerge more reactions which significantly affect the length of the two kinetic states.     

A priori error estimates for nonstationary optimal control problems with gradient state constraints

We are concerned with the discretization of semilinear parabolic optimization problems subject to constraints on the first derivative of the solution of the PDE. Constructing sequences of feasible controls for the dG(0)-cG(1) discretization of the problem and relying on a quadratric growth condtion, we show convergence orders as temporal and spatial mesh tends to zero. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Single and double hydrogen rearrangements in the mass spectra of O-ethyl,S-alkyl methanephosphonothioates

Whereas the oxygen analogues of the title series gives rise to double hydrogen rearrangement on electron-impact, alkylthiophosphonates show in addition a McLafferty rearrangement. The quantitative relationship between these two rearrangements in the thio series is dependent upon the chain length and branching on the alkyl group attached to sulphur. Comparison of the mass spectra of these compounds indicates that in the pathway of the double hydrogen rearrangement the hydrogen transferred to the sulphur atom originates primarily from the carbon δ to sulphur.     

Novel search for heavy nu mixing from the beta+ decay of 38mK confined in an atom trap

A new technique, full neutrino momentum reconstruction, is used to set limits on the admixture of heavy neutrinos into the electron neutrino. We measure coincidences between nuclear recoils and positrons from the beta decay of trapped radioactive atoms and deduce the neutrino momentum. A search for peaks in the reconstructed recoil time-of-flight spectrum as a function of positron energy is performed. The admixture upper limits range from 4 x 10(-3) to 2 x 10(-2) and are the best direct limits for neutrinos (as opposed to antineutrinos) for the mass region of 0.7 to 3.5 MeV.     

Advances in pulsed-laser atom probe: instrument and specimen design for optimum performance.

The performance of the pulsed-laser atom probe can be limited by both instrument and specimen factors. The experiments described in this article were designed to identify these factors so as to provide direction for further instrument and specimen development. Good agreement between voltage-pulsed and laser-pulsed data is found when the effective pulse fraction is less than 0.2 for pulsed-laser mode. Under the conditions reported in this article, the thermal tails of the peaks in the mass spectra did not show any significant change when produced with either a 10-ps or a 120-fs pulsed-laser source. Mass resolving power generally improves as the laser spot size and laser wavelength are decreased and as the specimen tip radius, specimen taper angle, and thermal diffusivity of the specimen material are increased. However, it is shown that two of the materials used in this study, aluminum and stainless steel, depend on these factors differently. A one-dimensional heat flow model is explored to explain these differences. The model correctly predicts the behavior of the aluminum samples, but breaks down for the stainless steel samples when the tip radius is large. A more accurate three-dimensional model is needed to overcome these discrepancies.