Doklady Physics最新文献

The equations of state of epoxy resin, carbon-fiber composite, and carbon at high pressures of the megabar range have been developed. The principle of additivity for calculating of the mixed shock adiabat of carbon-fiber composite based on the shock adiabats of epoxy resin and the high-pressure carbon phase is considered. It is concluded that the additivity principle is applicable for calculating the shock adiabats of polymer composite materials in the entire studied pressure range.

This research focuses on the Gd-doped carbon alumina nanospheres manufactured through a hydrothermal synthesis routes for their application in drug delivery. A facile two-step hydrothermal process was used to form the alumina spheres. In the initial stage at 90°C, gadolinium chloride hexahydrate was achieved through gadolinium oxide with the excess of hydrochloric acid. In the final stage, the formation of Gd-doped alumina in the hydrothermal reactor, followed by a combination of aluminum nitrate nanohydrate, glucose, gadolinium chloride and annealed at 450°C in the furnace, was achieved. The structural characterization of the powdered sample was performed with the help of SEM and XRD. The results of XRD showed the amorphous nature of alumina obtained after annealing. No peak of Gd was confirmed due to its lower concentration in the XRD pattern. The broad diffraction peaks of alumina were observed due to the high water content and weak crystalline structure. The outcomes of SEM showed that the synthesized Gd-doped alumina possessed spherical morphology. Before annealing, the average size was observed to be 1.69 µm. The composition analysis was done through EDX which confirmed the existence of aluminum, oxygen, and Gd. The functional group of PEG-coated alumina has been examined with the help of FTIR spectroscopy. The MTT assay has confirmed that the sample is biocompatible and can be used as a drug carrier.

The symmetries of the classical Heisenberg model are investigated. It is shown that such symmetries are groups of conformal transformations and rotations. The invariance of vortex structures with respect to the rotation group is studied. Application of the found transformations of the field rotation group to the previously found solutions of the Heisenberg model (such as instantons, vortex “targets” and “spirals”) generates other structures, which are also solutions to this model, the properties of which are determined by the original structures. which are also solutions of this model, with the properties determined by the original structures.

The results of a study of the elemental composition of thin films of aluminum nitride from the ratio of argon and nitrogen fluxes are presented. Aluminum nitride films were obtained by magnetron sputtering of an aluminum target in an atmosphere of a mixture of gases, that is, argon and nitrogen.

Numerical simulation is widely used in the study of energy exchange between the arc and the gas flow in arc-quenching devices of HV gas-blast circuit breakers. In the high-current phase, the main factor that influences energy exchange is radiation. Numerical models used to describe radiative heat transfer include an absorption coefficient, which depends on many parameters. The main parameters are the temperature and pressure of the gas and the radius of the plasma column. In this paper, the absorption coefficient for the main arc-extinguishing media was investigated: dry air (N₂), SF₆, CO₂ in the temperature range of 300—30 000 K and pressures of 1–30 atm with plasma column radii in the range of 1–40 mm.

The conventional derivation of the equations of motion in mechanics and the field equations in field theory is based on the principle of least action with a proper Lagrangian. For a time-independent Lagrangian, the function of coordinates and velocities, called energy, is constant. This paper presents a different approach – derivation of the general form of the equations of motion that ensure the constancy of the energy given as a function of generalized coordinates and corresponding velocities. It is shown that these are the Lagrange equations with additional gyroscopic forces. The derivation explicitly uses the important fact that the energy is given as a function on the tangent bundle of the configuration manifold. The Lagrangian is derived from a known energy function. It is proposed to develop generalized Hamilton and Lagrange equations without using variational principles. The new technique is used to derive some equations.

The spatial motion of a mechanical system consisting of a rigid body and a moving point mass, interacting with each other by means of unspecified internal forces, has been studied. The task is to construct such a trajectory for a point mass moving along which a rigid body under the influence of the force of interaction with this mass that changes its orientation in space according to a known program. It is assumed that there are external forces acting on both objects, which are specified as functions of time. A system of three first-order ordinary differential equations, resolved with respect to derivatives, is obtained, which allows one to solve the problem. These relationships can be used to control spacecraft and robotic systems.

Changes in the surface composition of silicon carbide under hydrogen ion bombardment were studied based on the method of calculating the component composition and thickness of the layer of two-component targets that changed as a result of stoichiometric sputtering under irradiation with light ions. The thickness of the modified layer and its component composition were calculated. The calculations showed that the surface layers are depleted of carbon, which is consistent with the experimental results.

This article considers the possibilities of organizing an arc discharge between graphite electrodes in kerosene with argon supply to the discharge area as applied to the synthesis of carbon nanostructures. The presence of argon was dictated by the conditions of maintaining a low-current discharge in a liquid medium with low viscosity. It is shown that an argon–hydrocarbon arc discharge in kerosene can serve as an effective tool for synthesizing nanodiamonds. The synthesized nanostructures look like a chain of figures that are approximately identical in shape and size. Moreover, these chains are not interrupted anywhere, making up a kind of crystal of nanodiamonds. This may be due to the entry of a particle into a liquid, from the other end of which a new particle begins to form. The synthesized nanodiamonds have sizes from 40 to 100 nm and are built into a linear row one after another. The most interesting thing about these results is that in the immediate vicinity there are no other nanostructures except nanodiamonds, which may be due to the presence of hydrogen, which reacts with unbound carbon atoms and removes them from the discharge area.

The magnetism of ZnSe supercells doped with 3d transition metals was investigated using the density functional theory. An analysis of the electronic properties of Zn_1–xMe_xSe systems showed additional peaks at the Fermi level due to Me²⁺ 3d levels. The computed magnetic moments for the Me_xZn_1–xSe supercell systems were found to be 4.0 µ_B for Cr_xZn_1–xSe, Fe_xZn_1–xSe, and Ni_xZn_1–xSe, and the main contribution to the magnetization of these systems is from Me d states. First-principles simulation of total energies for ferromagnetic and antiferromagnetic phases indicated the ferromagnetic phase stability of the Cr_xZn_1–xSe, Fe_xZn_1–xSe, and Ni_xZn_1–xSe systems. Our results demonstrated that the magnetization of Me_xZn_1–xSe supercell systems strongly depends on the Me concentration. In addition, Curie temperatures were estimated for the investigated materials. The Cr_xZn_1–xSe and Ni_xZn_1–xSe systems are half-metallic ferromagnetic materials with higher Curie temperatures. The Cr_xZn_1–xSe and Ni_xZn_1–xSe compounds are promising materials for spintronics and Fe_xZn_1–xSe is a paramagnetic compounds and a useful candidate for optoelectronic devices.