Volgograd State University

The peculiarity of mapping the memory of the central processing unit (CPU) to the memory of the graphics processing unit (GPU) is discussed in the case of its dynamic allocation using OpenACC directives. The problem is that the array is not placed contiguously in memory. Therefore, the program associates all bytes of the computer's RAM between the start and end elements of the dynamic array with bytes of the GPU's memory, regardless of whether all of these bytes are actually occupied by the array elements. This leads to an unjustified and unpredictable increase in the size of the GPU memory allocated to store the dynamic array. Our simulations show that the increase in memory size can reach two orders of magnitude. The source code for dynamic allocation of a contiguous block of memory for two-dimensional arrays in C is given. This approach can be easily generalized to the case of an arbitrary number of dimensions. Testing of the described method showed that the sizes of dynamic arrays in the memory of the central and graphic processors coincide.

Symmetry-breaking charge transfer (SBCT) has traditionally been studied in multichromophore donor-acceptor systems. Recent experimental observations in a centrosymmetric acene derivative lacking donor-acceptor structure challenge this paradigm, revealing activation of Laporte-forbidden transitions in polar solvents - a key signature of SBCT. Here, we develop a model for solvation-driven symmetry breaking in centrosymmetric, non-donor-acceptor compounds. The model considers two excited states of opposite parity, whose quantum superposition yields a state with a non-zero dipole moment. Polar solvents stabilize these mixed states, leading to symmetry breaking when the total reorganization energy exceeds half of the energy gap between the even and odd excited states. The key difference from donor-acceptor systems is the smallness of the dipole moment, which leads to significantly lower reorganization energies. Therefore, SBCT is possible if the energy gap between the lowest excited states of different parities is small enough. The model also predicts nonlinearity in Lippert-Mataga plots as the excited state dipole moment increases with increasing solvent polarity. These results provide a general framework for understanding symmetry breaking in centrosymmetric molecules without charge transfer bands and suggest that strategic functionalization with polarizable substituents, rather than the incorporation of strong donor-acceptor moieties, may be a powerful strategy for developing materials with environmentally responsive photophysical properties.

Metal-functionalized carbon nanotubes (CNTs) have emerged as versatile nanostructures with tunable properties for energy conversion, storage, and environmental remediation.

We present a unified theoretical model for the nonlinear terahertz response of an excited octupolar molecule in an electromagnetic field. The model incorporates strong vibronic interactions (the Jahn-Teller effect) and dipole-field interaction, enabling a comprehensive analysis of the zeroth (permanent), first, and second harmonics of the induced molecular dipole moment. A key finding is the contrasting response of the harmonics to rotation of the wave's polarization plane: the first-harmonic component of the dipole moment remains locked collinear to the electric field, whereas the zeroth- and second-harmonic components rotate in the opposite direction at twice the angle. This counter-rotation originates from the C3 symmetry of the molecule and provides for arbitrary mutual orientation of the first-harmonic component relative to the zeroth- and second-harmonic components, thereby enabling direct measurements of these two contributions. Moreover, the response exhibits strong resonances at well-defined frequencies governed by the vibronic interaction parameters, giving rise to clearly identifiable spectral features.

This study investigates the unsteady gas flow structure in a cyclone separator using high-resolution Large Eddy Simulation (LES). Unlike traditional approaches, a method for analyzing velocity field dynamics based on velocity increments is proposed and validated. This technique enables the identification of coherent structures and high-frequency pulsations even on relatively coarse computational grids-a task beyond the capabilities of classical RANS models. Comparative analysis reveals that standard two-equation isotropic turbulence models systematically overestimate tangential velocity near the walls, suggesting they should be used with caution in cyclone applications. While the anisotropic RSM provides better agreement for the mean tangential velocity, it fails to capture the episodic "superbursts" and near-wall streaks resolved by LES. Numerical experiments revealed two distinct dynamic regimes in the conical section: continuous background pulsations caused by stochastic vortex migration and periodic superbursts triggered by vortex core-wall interactions. Special emphasis is placed on the identification of near-wall velocity streaks resulting from hydrodynamic instability in the viscous sublayer. It is shown that the unsteadiness and subsequent bursting of these structures induce high-frequency gas pulsations directly at the wall, which can significantly affect the dynamics of solid particles near the surfaces. These findings provide new insights into turbulent transport in swirling flows and establish a robust framework for further investigation of separation mechanisms.