Том 63, № 8 (2018)

Warm dense hydrogen is investigated by the ab initio molecular dynamics method near the fluid–fluid phase transition. The metastable states are calculated along isotherms of 700 and 1000 K. The obtained pressure ranges of metastable states are 0.47 and 0.32 Mbar, respectively. Their existence indicates that this transition is a first-order phase transition.

A procedure for filtering images corrupted by mixed (additive-impulsive) noise has been substantiated and implemented for the first time. The novel method is characterized by the following stages: the detection and filtering of pixels corrupted by noise impulses, the image filtering in three-dimensional (3D) discrete cosine transform (DCT) space, and the final image processing stage in which the errors of the previous stages are corrected and the image edges and details are reconstructed. A physical interpretation of the filtering procedure under mixed noise conditions is given, and a filtering block diagram has been developed. Simulations of the proposed image filtering method have confirmed the advantage of the novel filtering scheme in terms of generally recognized criteria: the structural similarity index measure and the peak signal-to-noise ratio as well as when visually comparing the filtered images.

New formulations of the optimal shock isolation problem for an object on a movable base are proposed. These formulations take into account the uncertainty of information about the shock (impact) pulse applied to the base and allow anticipating control for the shock isolator. A guaranteeing control law that minimizes the maximum of the absolute value of the displacement of the object relative to the base for the worst disturbance is sought. For a class of external disturbances that reflects a number of typical features of impact pulses, the optimal control laws and optimal anticipation times are found.

In this paper, the viewpoint is expressed that the structure of a spontaneously radiating shock waves is a waveguide along which perturbations propagate. As usually, the perturbation velocity can be determined by the dispersion equation obtained from the relations for shocks. The perturbation velocity along the waveguide generally does not coincide with the above perturbation velocity and the envelope velocity does not coincide with the phase velocity of the waves.

The problem of stable equilibrium of a Bernoulli–Euler beam with both ends fixed positioned in an electrostatic field under the action of a pulse laser is considered. The initial equilibrium position under the action of the electrostatic field has been obtained. It has been shown that there exist either two equilibrium positions of this kind—stable and unstable ones—or none in a sufficiently strong electric field. The temperature field in the beam under the action of a laser pulse has been found. The possibility to lose the stability of equilibrium under heating of the element by a laser pulse is suggested for the first time. Regions corresponding to the stability of the aforesaid equilibrium position in the space of pulse parameters have been determined.