Recombination of polyatomic ester peroxy radicals in solution

Termination rate constants of peroxy radicals of seven polyatomic esters in benzene and perflouorooctane media have been measured by pulse photolysis. Recombination of peroxy radicals for all esters examined proves to be diffusion controlled. Reactivity of peroxy radicals in the termination reaction grows with increasing number of ester groups.

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On similitude of near wall turbulence in viscous sublayer

Power spectral density (PSD) of wall velocity gradient fluctuations has been measured using electrochemical (electrodiffusion) method in two rectangular channels with different hydraulic diameters and aspect ratio. The problem of the probes inertia at high frequency range has been smoothed by means of the transfer function; the reliability of the obtained results is justified by using of two circular probes with different diameter. For studied range of Reynolds numbers (6 × 10³ < Re _h < 4 × 10⁴) all spectra functions tend to a unique curve when a suitable dimensionless coordinates are used. These coordinates depend on the mean value of the velocity gradient S, the intensity of the velocity gradient fluctuations [`(s￠² )]overline {s'^2 } and the liquid viscosity ν, only. Thus, the obtained results reveal the similitude of the turbulence in the viscous sublayer with respect to Re number and flow geometry. Sure, this hypothesis should be tested with more representative base of experimental data. The revealed similitude can be important for chemical engineering applications. Indeed, for these applications the Reynolds numbers are rather small and correspond to the studied range and the intensity of the velocity gradient fluctuations are well related with the mean value of the velocity gradient value. So, the knowing of the mean velocity gradient S allows the prediction of the PSD of the velocity gradient fluctuations, if the viscosity of the fluid ν is known.     

Temperature parameters in the fragmentation of carbon ions at the energy of 0.6 GeV/nucleon

Momentum distributions of nuclear fragments at an angle of 3.5° in the interaction of 0.6-GeV/nucleon carbon ions with a beryllium target are measured in the FRAGM experiment on the ITEP-TWAC facility. The measured spectra are used for testing predictions of four ion–ion interaction models: BC, QMD, INCL, and LAQGSM03.03, and for comparison with the analytical parameterization within the thermodynamic concept of fragmentation.     

Estimation of MEA parameters and prediction of PEM fuel cells electrical performances using numerical modelling

In this paper, a coupled model of transfer phenomena within Proton Exchange Membrane Fuel Cell (PEMFC) developed from Stefan-Maxwell (in the diffusion and active layers), Butler-Volmer (in the active layer), and water mass transport (in the electrolyte membrane) equations is presented. This modeling allows interpreting experimental results, prediction of PEMFC electrical performances and guiding perspective investigations on optimization of PEMFC. The model helps the research of dominating sensitivity parameters, as well as the estimation of some badly known MEA (Membrane Electrode Assembly) parameters using fuel cell tests.     

Nuclear Fragments in 12 C + 9 Be Interactions at an Energy of 2 GeV per Nucleon

Differential cross sections for the production of nuclear fragments at an angle of 3.5° in the fragmentation of 2-GeV/nucleon carbon ions on a beryllium target were measured in the FRAGM experiment performed at the ITEP-TWA heavy-ion accelerator-accumulator complex. The predictions of four Monte Carlo models of ion-ion interactions (BC, INCL, LAQGSM, and QMD) were tested on the basis of a comparison with the momentum spectra of fragments. Successes and drawbacks of these models are discussed. The energy spectra of protons and 3He nuclei in the cumulative region in the projectile rest frame are well described by an exponential dependence, which make it possible to estimate temperature parameters of their emission source.     

Performance and instabilities of proton exchange membrane fuel cells

Performance of proton exchange fuel cells with different membrane and electrode assembly (MEA) is studied. It is shown that MEA fabricated with catalyst plasma pulverization technology has the maximum performance. Some instabilities in the cell performance, observed with time, are probably due to periodic cathode flooding. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 5, pp. 525–534. The text was submitted by the authors in English.