Predicting the laminar to turbulent transition is an important aspect of computational fluid dynamics because of its impact on skin friction. Traditional transition prediction methods such as local stability theory or the parabolized stability equation method do not allow for the consideration of strongly non-parallel boundary layer flows, as in the presence of surface defects (bumps, steps, gaps, etc.). A neural network approach, based on an extensive database of two-dimensional incompressible boundary layer stability studies in the presence of gap-like surface defects, is used. These studies consist of linearized Navier–Stokes calculations and provide information on the effect of surface irregularity geometry and aerodynamic conditions on the transition to turbulence. The physical and geometrical parameters characterizing the defect and the flow are then provided to a neural network whose outputs inform about the effect of a given gap on the transition through the ${\rm \Delta} N$ method (where N represents the amplification of the boundary layer instabilities).

The structural, vibrational, and optoelectronic properties of sol–gel synthesized Zn1−x(Al0.5Si0.5)xO nanoparticles were investigated. The X-ray diffraction studies of the samples confirmed the hexagonal wurtzite phase with the space group P63mc. No significant changes were observed in the lattice parameters. The increase in the intensity of $E_{{\rm{high}}}^2$ Raman mode observed at 438 cm−1 indicates a decrease in the crystallite size. The reduction in the deep-level emission band with the introduction of Al/Si indicates a decrease in intrinsic defects for the codoped sample. A unique electron paramagnetic resonance signal at g= 1.96 follows the same trend as the green luminescence, and its evolution was shown to probe the oxygen vacancy concentrations. I–V characteristics curve confirm the increase in the conductivity for the codoped samples. To evaluate the role of surface defects, ultraviolet photoresponse behavior as a function of time was also studied, and an increase in the photocurrent was observed. The slow decay and rise in the photocurrent are because of multiple trapping by interstitial defects. A relatively faster response time was observed with the substitution of Al/Si. It has been observed that prepared nanomaterials are suitable for optoelectronic devices.

A systematic analysis was carried out to study the effect of shock waves on copper sulfate crystal in such a way that its optical properties and surface morphological properties were examined for different number of shock pulses (0, 1, 3, 5, and 7) with the constant Mach number 1.7. The test crystal of copper sulfate was grown by slow evaporation technique. The surface morphological and optical properties were scrutinized by optical microscope and ultraviolet–visible spectrometer, respectively. On exposing to shock waves, the optical transmission of the test crystal started increasing from the range of 35–45% with the increase of shock pulses and thereafter started decreasing to 25% for higher number of applied shocks. The optical band transition modes and optical band gap energies were calculated for pre- and post-shock wave loaded conditions. The experimentally obtained data prove that the optical constants such as absorption coefficient, extinction coefficient, skin depth, optical density, and optical conductivity are strongly altered, so also the optical transmission due to the impact of shock waves. Hence, shock wave induced high transmission test crystal can be used as an appropriate candidate for ultraviolet light filter applications.