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Aluminium 6061 deposited by high pressure cold spray was analysed using a transmission electron microscope (TEM) to characterise its microstructure and response to annealing to 450°C in the plane of the deposition and perpendicular to the deposited layers. The cold sprayed deposition was also analysed with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) analysis and differential scanning calorimeter (DSC). Segregation of the solute atoms (Mg and Si) at the grain boundaries during cold spraying was seen to play a crucial role in stabilising the deformation substructure until specific temperatures, and was found to have a significant effect on the annealing behaviour of the microstructure in the two different directions.

This investigation concerns numerical calculation of turbulent forced convective heat transfer and fluid flow in straight ducts using the RNG (Re-Normalized Group) turbulence method.A computational method has been developed to predict the turbulent Reynolds stresses and turbulent heat fluxes in ducts with different turbulence models. The turbulent Reynolds stresses and other turbulent flow quantities are predicted with the RNG κ-ε model and the RNG non-linear κ-ε model of Speziale. The turbulent heat fluxes are modeled by the simple eddy diffusivity (SED) concept, GGDH and WET methods. Two wall functions are used, one for the velocity field and one for the temperature field. All the models arc implemented for an arbitrary three dimensional duct.Fully developed condition is achieved by imposing cyclic boundary conditions in the main flow direction. The numerical approach is based on the finite volume technique with a non-staggered grid arrangement. The pressure-velocity coupling is handled by using the SIMPLEC-algorithm. The convective terms are treated by the QUICK, scheme while the diffusive terms are handled by the central-difference scheme. The hybrid scheme is used for solving the κ and ε equations.The overall comparison between the models is presented in terms of friction factor and Nusselt number. The secondary flow generation is also of major concern.

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Cutting states associated with the orthogonal cutting of stiff cylinders are identified through an analysis of the singular values of a Toeplitz matrix of third order cumulants of acceleration measurements. The ratio of the two pairs of largest singular values is shown to differentiate between light cutting, medium cutting, pre-chatter and chatter states. Sequences of cutting experiments were performed in which either depth of cut or turning frequency was varied. Two sequences of experiments with variable turning frequency and five with variable depth of cut, 42 cutting experiments in all, provided a database for the calculation of third order cumulants. Ratios of singular values of cumulant matrices find application in the analysis and control or orthogonal cutting.

We apply a new technique, multiseed stimulated rotational Raman scattering, to the wave-front control of Raman-converted light when the Raman gain–length product is large enough to produce significant conversion beyond the first-Stokes order. For rotational Raman scattering, such as that which dominates in atmospheric propagation, the polarizations of adjacent Stokes orders may be made circular and opposite in order to eliminate Stokes–anti-Stokes coupling and thereby minimize losses that are due to amplified noise. A parametric process that couples four distinct waves recursively generates a fourth wave when any three waves are incident. Thus at least two seeds (e.g., first and second Stokes) are necessary to start the process. Computer simulations then show that, within limitations imposed by diffraction and competition from noise, the wave fronts of higher-order Stokes fields are determined by those of the incident fields. Starting from a 250-nm laser and using subatmospheric H_2 as a Raman medium, we generate multiple seeds with alternate polarization helicities on the S(1) rotational transition. Multiseed experiments showed that a good-beam-quality core was converted and amplified but that a poor-quality background beam was amplified as well. With the aid of computer simulations, we interpret this effect as resulting from the competition between seeded light and noise, the noise being favored by its buildup during the delay until the arrival of the leading edges of the seed pulses. The beam’s additional loss of quality is attributable to the growth of aberrations from smaller aberrations and intensity variations that are present in the incident beams.

The information dimension, D(0), of attractors associated with orthogonal turning is determined from experimental tool-workpiece relative acceleration data. Let E≡dimension of a delay coordinate space, n≡number of generic data points and m≡ number of reference points on the attractor. It is shown that properties of D(0) as a function of E, denoted by D(0):E, are unchanging, invariant, over large intervals of n and m. The qualitative properties of D(0):E discriminate between various cutting cases. This discrimination can be based on relatively small data sets. The computation of D(0) is shown to be robust in the sense that estimated values of D(0) are invariant or slowly varying over intervals of n and m.

Chatter and non-chatter cutting states, associated with the orthogonal cutting of stiff metal cylinders, are identified through an analysis of the ratios of the mean absolute deviations of details of the biorthogonal 6,8 wavelet decomposition of cutting force measurements. Sequences of cutting experiments were performed in which either depth of cut or turning frequency was varied. For light and medium cutting the mean absolute deviations of the ratios of detailsd3andd4is less than 7 while for chatter it is greater than 15. The kurtosis of detaild3is shown to identify transitions to chatter.

We report excitation of the 3P1 and 3P2 metastable states of the ground configuration of lead atoms by the homogeneous oxidation by oxygen of acetylene or cyanogen containing tetramethyl lead (TML). The population of the excited states is monitored by absorption spectroscopy. Our results indicate that the reactions excite a considerable fraction of free lead atoms to these metastable states. Evidence is presented that the population of the metastable states in the oxyacetylene reaction is due to chemiexcitation.

The information dimension, D(0), of attractors associated with orthogonal turning is determined from experimental tool-workpiece relative acceleration data. Let E=dimension of a delay coordinate space, n=number of generic data points and m= number of reference points on the attractor. It is shown that properties of D(0) as a function of E, denoted by D(0):E, are unchanging, invariant, over large intervals of n and m. The qualitative properties of D(0):E discriminate between various cutting cases. This discrimination can be based on relatively small data sets. The computation of D(0) is shown to be robust in the sense that estimated values of D(0) are invariant or slowly varying over intervals of n and m.

We consider hot luminescence from a quantum wire (QWR) due to electrons that are excited by a narrow band, noncoherent cw laser, to the close vicinity of the threshold for optical LO phonon emission. In this case one has to resort to quantum kinetic equations (QKEs), since the level broadening close to the threshold is large, due to the singular 1D density of states. The QKEs are formulated using a recipe that we derived for the generalization of the Boltzmann equation (BE). The luminescence spectral distribution is calculated using these QKEs. It is shown that the scale that determines the quantum behavior of the system differs from what one would expect from simple level broadening considerations.