Langmuir wave linear evolution in inhomogeneous nonstationary anisotropic plasma

Equations describing the linear evolution of a non-dissipative Langmuir wave in inhomogeneous nonstationary anisotropic plasma without magnetic field are derived in the geometrical optics approximation. A continuity equation is obtained for the wave action density, and the conditions for the action conservation are formulated. In homogeneous plasma, the wave field E universally scales with the electron density N as E ~ N^{3/4}, whereas the wavevector evolution varies depending on the wave geometry

Semiclassical treatment of logarithmic perturbation theory

The explicit semiclassical treatment of logarithmic perturbation theory for the nonrelativistic bound states problem is developed. Based upon $\hbar$-expansions and suitable quantization conditions a new procedure for deriving perturbation expansions for the one-dimensional anharmonic oscillator is offered. Avoiding disadvantages of the standard approach, new handy recursion formulae with the same simple form both for ground and exited states have been obtained. As an example, the perturbation expansions for the energy eigenvalues of the harmonic oscillator perturbed by $\lambda x^{6}$ are considered.Comment: 6 pages, LATEX 2.09 using IOP style

Polarization of the vacuum of a quantized scalar field by an impenetrable magnetic vortex of finite thickness

We consider the effect of the magnetic field background in the form of a tube of the finite transverse size on the vacuum of the quantized charged massive scalar field which is subject to the Dirichlet boundary condition at the tube. It is shown that, if the Compton wavelength associated with the scalar field exceeds considerably the transverse size of the tube, then the vacuum energy which is finite and periodic in the value of the magnetic flux enclosed in the tube is induced on a plane transverse to the tube. Some consequences for generic features of the vacuum polarization in the cosmic-string background are discussed.Comment: 13 pages, 10 figures, journal version, minor changes, some references adde

Evolution of microstructure and mechanical properties of a CoCrFeMnNi High-entropy alloy during high-pressure torsion at room and cryogenic temperatures

High-pressure torsion is applied to a face-centered cubic CoCrFeMnNi high-entropy alloy at 293 and 77 K. Processing by HPT at 293 K produced a nanostructure consisted of (sub)grains of ~50 nm after a rotation for 180°. The microstructure evolution is associated with intensive deformation-induced twinning, and substructure development resulted in a gradual microstructure refinemen

Effect of multiaxial forging on microstructure and mechanical properties of Mg-0.8Ca alloy

It was shown that multiaxial forging with continuous decrease of temperature from 450°C to 250°C turns coarse structure of the Mg-0.8Ca alloy in homogenized state with grain size of several hundreeds μm into fine structure with average grain size of about 2.1 μm. Refinement of structure is accompanied by drastic increase of mechanical properties: tensile yield strength increases from 50 MPa to 193 MPa, ultimate tensile strength increases from 78 to 308 MPa and elongation to fracture increases from 3.0% to 7.2%. The microstructural evolution during multiaxial forging is studied using optical microscopy, scanning electron microscopy and EBSD analysis. The mechanisms responsible for refinement of microstructure are discusse

Structure and hardness of B2 ordered refractory AlNbTiVZr0.5 high entropy alloy after high-pressure torsion

High-pressure torsion (HPT) at room temperature was applied to an AlNbTiVZr0.5 refractory high entropy alloy. In the initial as-cast condition the alloy was composed of a coarse-grained B2 matrix phase and a continuous network of C14 Laves phase particles with the volume fraction of 19%. HPT resulted in the formation of a nanocrystalline structure in the B2 matrix with an average size of grains/subgrains of 25 nm after 5 revolution

Effect of Cr and Zr on phase stability of refractory Al-Cr-Nb-Ti-V-Zr high-entropy alloys

The effect of annealing at 800 C or 1000 C for 100 h on the structure and mechanical properties of refractory AlCrxNbTiV and AlNbTiVZrx (x ¼ 0e1.5) high-entropy alloys was studied. The differences in the behavior of the Cr/Zr-containing alloys and the relationships between the phase composition and mechanical properties of the alloys were discusse

Structure and mechanical properties of B2 ordered refractory AlNbTiVZrx (x=0-1.5) high-entropy alloys

Structure and mechanical properties of the AlNbTiVZrx (x=0; 0.1; 0.25; 0.5; 1; 1.5) refractory high-entropy alloys were investigated after arc melting and annealing at 1200°C for 24 h. The AlNbTiV alloy had a B2 ordered single phase structure. Alloying with Zr resulted in (i) change of the degree of order of the B2 phase; and (ii) precipitation of the Zr5Al3 and C14 Laves ZrAlV phase

Aging behavior of the HfNbTaTiZr high entropy alloy

The HfNbTaTiZr high entropy alloy was produced by vacuum arc melting, homogenized at 1200 C, and annealed at 600-1000 C for 1-100 h. Structure and microhardness of the annealed alloy were investigated. A strong increase of microhardness after aging treatment at 600 C was found. Formation of second hcp phase particles in the bcc matrix after annealing at 600 and 800 C was also revealed. Effect of precipitation of second phase particles on microhardness was analyze

Effect of thermomechanical processing on microstructure and mechanical properties of the carbon-containing CoCrFeNiMn high entropy alloy

Microstructural evolution during cold sheet rolling to 80% thickness strain and annealing at 600-1100° C for 30 min of the CoCrFeNiMn high entropy alloy doped with 1 at.% of C and resulting mechanical properties of the alloy are reporte