Critical conditions of hydrogen-air detonation in partially confined geometry

This work presents the results of the large scale experiments with detonation propagating in hydrogen–air mixtures in partially confined geometries. The main aim of the work was to find the critical conditions for detonation propagation in semi-confined geometries with uniform and non-uniform hydrogen–air mixtures. The experimental facility consisted of rectangular 9 × 3 × 0.6 m channel open from the bottom, acceleration section and test section, safety vessel, gas injection and data acquisition system. Sooted plates technique was used as a witness of the detonation. The rectangular channel was placed in a 100 m³ safety vessel. For uniform hydrogen–air mixtures experiments with four different channel heights h were performed: 8, 5, 3 and 2 cm. The critical hydrogen–air mixture height h* for which the detonation may propagate in a layer is close to the 3 cm which corresponds to approximately three detonation cell sizes. For non-uniform hydrogen–air mixture with hydrogen concentration slope equal approximately ?1.1%H₂/cm the critical hydrogen concentration at the top of the layer is approximately equal 26% and the mean detonation layer height is close to the 8.5 cm corresponding to the hydrogen concentration at the bottom of the layer approximately equal 16–17%.     

Neural network modelling of adsorption isotherms

This paper examines the possibility to use a single neural network to model and predict a wide array of standard adsorption isotherm behaviour. Series of isotherm data were generated from the four most common isotherm equations (Langmuir, Freundlich, Sips and Toth) and the data were fitted with a unique neural network structure. Results showed that a single neural network with a hidden layer having three neurons, including the bias neuron, was able to represent very accurately the adsorption isotherm data in all cases. Similarly, a neural network with four hidden neurons, including the bias, was able to predict very accurately the temperature dependency of adsorption data.     

A note on knowledge discovery using neural networks and its application to credit card screening

We address an important issue in knowledge discovery using neural networks that has been left out in a recent article “Knowledge discovery using a neural network simultaneous optimization algorithm on a real world classification problem” by Sexton et al. [R.S. Sexton, S. McMurtrey, D.J. Cleavenger, Knowledge discovery using a neural network simultaneous optimization algorithm on a real world classification problem, European Journal of Operational Research 168 (2006) 1009–1018]. This important issue is the generation of comprehensible rule sets from trained neural networks. In this note, we present our neural network rule extraction algorithm that is very effective in discovering knowledge embedded in a neural network. This algorithm is particularly appropriate in applications where comprehensibility as well as accuracy are required. For the same data sets used by Sexton et al. our algorithm produces accurate rule sets that are concise and comprehensible, and hence helps validate the claim that neural networks could be viable alternatives to other data mining tools for knowledge discovery.     

The rôle of particle transfer in large-angle scattering of 1p-shell nuclei

The scattering of different 1p shell heavy ions on nuclei of the same species has been measured in the whole angular range up to 174°. Various pairs of interacting nuclei have been selected according to the different complexities of their properties which can influence the scattering through higher-order processes to different degrees. In general, the observed rise of the cross section in the backward region is satisfactorily described as a single-step transfer reaction. Second-order processes and compound-nucleus contributions are of no practical importance for the explanation of the elastic scattering data. The performed analysis, however, leaves some features in the experimental angular distributions not fully and satisfactorily understood.     

K + production in proton and deuteron induced reactions at subthreshold energies

The production ofK ⁺ mesons in proton-nucleus and deuteron-nucleus collisions is analyzed with respect to one-step nucleon-nucleon (NN → N ΛK ⁺),Δ- nucleon (ΔN → N Λ K⁺) and two-step pion-nucleon (πN → K ⁺ Λ) production channels on the basis of experimental ground state momentum distributions and free on-shell production processes. Whereas forK ⁺ production in proton-nucleus reactions the secondary channelπN clearly dominates at subthreshold energies, meson and nucleon induced channels are of similar magnitude in deuteron-nucleus reactions. Contrary to nucleus-nucleus collisions theΔ induced reaction channels are found to be of minor importance. The experimental differentiation of the underlying microscopic reaction channels appears possible via differential proton —K ⁺ coincidence measurements as shown in detail by the microscopic simulations including proton rescattering.     

The electric field gradient at the iron sites inβFeOOH

The temperature behaviour of the hyperfine parameters of iron in paramagnetic chlorine containingΒFeOOH is studied by⁵⁷Fe Mössbauer spectroscopy. Applying external magnetic fields, the sign and asymmetry parameterη of the electric field gradient (EFG) at the compound's two iron sites is determined. It is shown that an external field enhances the distributive character of the hyperfine parameters. Finally, heat treatment experiments allow new data on the nature of both iron coordination types to be presented.     

Über eine Verbesserung der Membran-Mikrobürette nach Gorbach

Ohne ZusammenfassungHerrn Univ.-Prof. Dr.Hans Lieb zum 80. Geburtstag gewidmet.     

Inclusive K+-meson production in proton-nucleus interactions

The production of K⁺-mesons in pA (A = D, C, Cu, Ag, Au) collisions has been investigated at the COoler SYnchrotron COSY-Jülich for beam energies T_p = 1.0-2.3 GeV. Double differential inclusive pC cross-sections at forward angles _{K^+} < 12^° as well as the target mass dependence of the K⁺ momentum spectra have been measured with the ANKE spectrometer. Far below the free NN threshold at T_NN = 1.58 GeV the spectra reveal a high degree of collectivity in the target nucleus. From the target mass dependence of the cross-sections at higher energies, the repulsive in-medium potential of the K⁺-mesons can be deduced. Using pN cross-section parameterisations from the literature and our measured pD data we derive a cross-section ratio (pnK⁺X)/(ppK⁺X) (3-4).     

Nuclear reactions of silver with 25.2 GeV 12C

Nuclear reactions induced in silver by 25.2 GeV ¹²C ions have been studied by the activation technique and compared with those induced by 300 GeV protons.