Cross-correlation of excitation functions for different fragments and different scattering angles in Al-27(F-19, x)y reactions

Excitation functions have been measured for different projectile-like fragments produced in Al-27(F-19,x)y reactions at incident energies from 110.25 to 118.75 MeV in 250 keV steps. Strong cross section fluctuations of the excitation functions are observed. The cross- correlation coefficients of the excitation functions for different atomic number Z and for different scattering angle theta(cm) have been deduced. These coefficients are much larger than the statistical theoretical calculated ones. This indicates that there are strong correlations between different exit channels in the dissipative heavy ion Collision of Al-27(F-19,x)y.

Transfer ionization of helium in collisions with Cq+ and Oq+ (q=1-3)

Cross-section ratios sigma(TI)/sigma(SC) of transfer ionization (TI) to single capture (SC) of Cq+- and Oq+-He (q = 1 - 3) collisions in the energy range of 15-440 keV/u (0.8-4.2 v(Bohr)) are experimentally determined. It is shown that sigma(TI)/sigma(SC) strongly depends on the projectile velocity, and there is a maximum for E(keV/u)/q(1/2) approximate to 150. Combining the Bohr-Lindhard model and the statistical model, a theoretical estimate is presented, in reasonable agreement with the experimental data when E(keV/u)/q(1/2) > 35.

Slow cross-symmetry phase relaxation in complex collisions

We discuss the effect of slow phase relaxation and the spin off-diagonal S-matrix correlations on the cross-section energy oscillations and the time evolution of the highly excited intermediate systems formed in complex collisions. Such deformed intermediate complexes with strongly overlapping resonances can be formed in heavy-ion collisions, bimolecular chemical reactions, and atomic cluster collisions. The effects of quasiperiodic energy dependence of the cross sections, coherent rotation of the hyperdeformed similar or equal to(3 : 1) intermediate complex, Schrodinger cat states, and quantum-classical transition are studied for Mg-24 + Si-28 heavy-ion scattering.

Exotic behavior of elastic scattering differential cross-sections of weakly bound nucleus F-17 at small angles

The differential cross-sections for elastic scattering of F-17 and O-17 on Pb-208 have been measured at Radioactive Ion Beam Line at Lanzhou (RIBLL). The variation of the logarithms of differential cross-sections with the square of scattering angles shows clearly that there exists a turning point in the range of small scattering angles (6 degrees-20 degrees) for F-17 having exotic structure, while no turning point was observed in the O-17 elastic scattering. The experimental results have been compared with previous data. Systematical analysis on the available data seems to conclude that there is an exotic behavior of elastic scattering differential cross-sections of weakly bound nuclei with halo or skin structure as compared with that of the ordinary nuclei near stable line. Therefore the fact that the turning point of the logarithms of differential cross-sections appears at small angle for weakly bound nuclei could be used as a new probe to investigate the halo and skin phenomenon.

Non-reproducibility of the cross sections of the products induced from dissipative reaction of F-19+Al-27

The differential cross sections of the dissipative products B, Q N, O, F, Ne, Na and Mg induced from the reactions of F-19+Al-27 at two incident energies have been measured at the HI-13 tandem accelerator, Beijing. In the case of a fixed beam incident energy 114MeV or 118.75MeV respectively, identical reaction system and the same detection system, 20 target points in steps of 2mm on(.)a 10mmx50mm rectangular Al foil have been bombarded. The experimental results indicate that the probability distribution of the cross sections is much wider than a standard Gaussian distribution. This non-reproducibility of the cross sections can't be interpreted by the statistical property of a finite count rate.

Effects of elastic and inelastic NN scattering cross sections on pi(-)/pi(+) ratios in heavy-ion collisions at intermediate energies

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model and the scaling model according to nucleon effective mass, effects of elastic and inelastic NN scattering cross sections on pi(-)/pi(+) in the neutron-rich reaction of Ca-48 + Ca-48 at a beam energy of 400 MeV/nucleon are studied. It is found that cross-section effects of both NN elastic and inelastic scatterings affect Delta(1232), pi(-) and pi(+) production, as well as the value of pi(-)/pi(+).

Calculations of cross sections of resonant two-photon transitions to the second excited 4f5d state in Pr3+: Y3Al5O12 using density matrix theory

The density matrix resonant two-photon absorption (TPA) theory applicable to laser crystals doped with rare earth ions is described. Using this theory, resonant TPA cross sections for transitions from the ground state to the second excited state of the 4f5d configuration in cm(4)s Pr3+:Y3Al5O12 are calculated. The peak value of TPA cross section calculated is 2.75 x 10(-50) cm(4)s which is very close to the previous experimental value 4 x 10(-50) cm(4) s. The good agreement of calculated data with measured values demonstrates that the density matrix resonant TPA theory can predict resonant TPA intensity much better than the standard second-order perturbation TPA theory.

A Generalized Soft-Sphere for Monte Carlo Simulation

A new collision model, called the generalized soft-sphere (GSS) model, is introduced. It has the same total cross section as the generalized hard-sphere model [Phys. Fluids A 5, 738 (1993)], whereas the deflection angle is calculated by the soft-sphere scattering model [Phys. Fluids A 3, 2459 (1991)]. In virtue of a two-term formula given to fit the numerical solutions of the collision integrals for the Lennard-Jones (6-12) potential and for the Stockmayer potential, the parameters involved in the GSS model are determined explicitly that may fully reproduce the transport coefficients under these potentials. Coefficients of viscosity, self-diffusion and diffusion for both polar and nonpolar molecules given by the GSS model and experiment are in excellent agreement over a wide range of temperature from low to high.

Influence of the Processing Conditions on the Characteristics of the Clad Layers Produced with Laminar Plasma Technology

Laminar plasma technology was used to produce ceramic hardened layers of Al2O3-40% mass Ni composite powders on stainless steel substrates. In order to investigate the influences of processing conditions on the morphologies of the surface modified layers, two different powder-feeding methods were tested, one with carrier gas called the powder injection method, and the other without carrier gas called powder transfers method. The microscopic investigations demonstrate that the cross-section of the clad layers consists of two distinct microstructural regions, in which the Al2O3 phases exhibit different growth mechanisms. When the powder transfers method is adopted, the number density and volume fraction of the Al2O3 particles increase considerably and their distributions exhibit zonal periodical characteristics. When the powder-feeding rate increases, the microstructure of the Al2O3 phases changes from a small globular to a long needle shape. Finite element simulations show that the transient thermo-physical features of the pool substances, such as solidification rate and cooling rate, influence strongly the mechanisms of the nucleation and the directional growth of the Al2O3 phases in the thermal processing.

Feasibility of Laminar Plasma-Jet Hardening of Cast Iron Surface

Nontransferred DC laminar plasma jets of stable flow and low impinging pressure acting on the substrate were used to heat W–Mo–Cu cast iron for phase transfer hardening of the surface layer. Substrates were heated in multipass with or without overlapping or heated with only single-pass. Surface morphologies of the molten trace and microstructure of the cross-section were observed, and the hardness distribution of the treated surface layer was examined. The surface layer of single-pass-heated specimen has an average hardness of about 900 HV0.1, while the specimen treated with multipass shows an average hardness of about 700 HV0.1, because of the heat effect from the neighboring pass treating, compared with the substrate hardness of about 300 HV0.1. The results demonstrate the stable and favorably controlled heating of the laminar plasma jet on the substrate surface and feasibility of using it as a tool for surface hardening of cast iron.

Experimental investigation on the chaotic phenomena in the wake of a natural thermal convection flow

Chaotic phenomena in the wake of thermal convection flow fields above a heating flat plate were investigated experimentally. A newly developed electron beam fluorescence technique (EBF) was used to simultaneously measure density fluctuation at 7 points in a cross section above the plate. Correlation dimensions, intermittence coefficients, Fourier spectrum have been obtained for different Grashof numbers. Spatial distribution of correlation dimensions are presented. The experimental result shows that there is a certain relationship between the density fluctuation and the Gr number. And time-spacial characteristic of chaos evolution is also given.

Investigation on Depth of Heat Affected Zone of Discharge Spot by High Repetitive Rate YAG Laser-Induced Discharge Texturing

It is known that the press formability and the elongation of laser textured sheet are improved, and the service life of textured roll is longer than that of the un-textured roll due to hardening of the treated surface. One of the goals to develop high repetitive rate YAG laser-induced discharge texturing (LIDT) is to get deeper hardening zone. By observing and measuring cross-section of LIDT spots in different discharge conditions, it is found that the single-crater, which is formed by the discharge conditions of anode, which is covered by an oil film and with rectangular current waveform, has the most depth of heat affected zone (HAZ) comparing with other crater shapes when discharge energy is the same. The depth of HAZ is mainly depends on pulse duration when the discharge spot is single-crater. The results are analyzed.

Characterization of Air-Water Two-Phase Vertical Flow by Using Electrical Resistance Imaging

The characterization of air-water two-phase vertical flow in a 12 m flow loop with 1.5 m of vertical section is studied by using electrical resistance tomography (ERT). By applying a fast data collection to a dual-plane ERT sensor and an iterative image reconstruction algorithm, relevant information is gathered for implementation of flow characteristics, particularly for flow regime recognition. A cross-correlation method is also used to interpret the velocity distribution of the gas phase on the cross section. The paper demonstrates that ERT can now be deployed routinely for velocity measurements and this capability will increase as faster measurement systems evolve.

Characters of Surface Deformation and Surface Wave in Thermal Capillary Convection

In the field of fluid mechanics, free surface phenomena is one of the most important physical processes. In the present research work, the surface deformation and surface wave caused by temperature difference of sidewalls in a rectangular cavity have been investigated. The horizontal cross-section of the container is 52 mmx42 mm, and there is a silicon oil layer of height 3.5 mm in the experimental cavity. Temperature difference between the two side walls of the cavity is increased gradually, and the flow on the liquid layer will develop from stable convection to un-stable convection. An optical diagnostic system consisting of a modified Michelson interferometer and image processor has been developed for study of the surface deformation and surface wave of thermal capillary convection. The Fourier transformation method is used to interferometer fringe analysis. The quantitative results of surface deformation and surface wave have been calculated from a serial of the interference fringe patterns.The characters of surface deformation and surface wave have been obtained. They are related with temperature gradient and surface tension. Surface deformation is fluctuant with time, which shows the character of surface wave. The cycle period of the wave is 4.8 s, and the amplitudes are from 0 to 0.55 mu m. The phase of the wave near the cool side of the cavity is opposite and correlative to that near the hot side. The present experiment proves that the surface wave of thermal capillary convection exists on liquid free surface, and it is wrapped in surface deformation.

Thermocapillary Effect in a Thermal Rheological Jet

The process of die swell in polymer jets is an important feature within polymer processing and can be explained through a study of its rheological effects. The existence of a thermocapillary effect, driven by the gradient of its surface tension, should be considered when examining a thermal jet that has a non-uniform temperature distribution on its free surface, as in various polymer processings. Both the rheological effect and thermocapillary effect on die swell can be studied numerically through a finite element method as used on a two-dimensional and unsteady model, in which a Coleman-Noll second-order fluid model is employed. The results show that the expanding angle depends on both the rheological property of the fluid and the pressure at the vessel exit. Although both the thermocapillary and the rheological effects contribute to the cross-section expansion of the fluid jet, the latter is more important in determining the expansion.