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.     

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.     

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.     

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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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.     

Comparative study of turbulent mass transfer in the viscous sublayer using electrochemical method and direct numerical simulations

In this study we present, analyze and compare the power spectral density of the wall shear stress in a turbulent plane channel flow obtained with different techniques. Experimentally the instantaneous wall shear stress was measured with the electrochemical technique using different probes, which give approximately the same results after applying the transfer function for correction of the probe??s inertia. Numerically, the time evolution of the wall shear stress has been determined using direct numerical simulations (DNS) and large eddy simulations (LES). The results of DNS are in a good agreement with the electrochemical flow measurements. However the power spectra of the wall shear stress obtained with LES shows deviations with respect to DNS at high frequencies because of the spatial filtering inherent to the LES technique.     

Quasielastic deuteron and triton knockout from lithium isotopes by intermediate-energy pions

Quasielastic deuteron and triton knockout from ⁶Li and ⁷Li nuclei that was induced by a π ^?-meson beam of momentum p ₀ = 0.72 and 0.88 GeV/c was studied under conditions of full kinematics. The experiment was performed at the Institute of Theoretical and Experimental Physics (ITEP, Moscow) by using a 3-m magnetic spectrometer equipped with spark chambers. The distributions with respect to the momenta of quasideuteron and quasitriton internal motion, the excitation-energy spectra of residual nuclei, and the effective numbers of quasideuterons in ⁶Li and ⁷Li nuclei were obtained.     

Statistical theory of turbulent mass transfer in electrochemical systems

The paper presents an overview of the statistical theory of turbulent mass transfer in electrochemical systems and some new results which generalize the previously obtained relations for the flows of complex geometry. The developed theory does not use traditional semi-empirical hypotheses and analogies, but directly addresses to the solving of the critical for turbulent transfer the closure problem. The mathematical procedure for solving of the closure problem makes use of new equations for the correlations between concentration and velocity fluctuations in different space points and at different time moments; the dumping of turbulent pulsations in the viscous sublayer allows to neglect high order moments and obtain a closed equation for the turbulent mass flux. In general, the relation between the turbulent mass flux and the mean concentration gradient is non-local. Using available experimental information, the non-local equation for the turbulent mass flux is reduced to the traditional local one and the functional form of the turbulent diffusion coefficient is obtained. It is demonstrated that Reynolds analogy cannot been used for the prediction of the turbulent diffusivity. Applications of the developed theory to chemical engineering and to electrochemical flow diagnostics (prediction of flow characteristics using limiting diffusion current measurements) are discussed.