Remanent states of small ferromagnetic cylinder

The internal magnetic structures of a cylinder are computed without prior assumption of axial symmetry. A three-dimensional magnetostatic solution is presented. A detailed distribution of the magnetization is obtained through numerical integration of the Landau-Lifshitz equation with the demagnetization field. Various entry conditions are used. Materials with small uniaxial anisotropy typically demonstrate vortex structures, while a higher anisotropy leads to the formation of concentric cylindrical magnetic bubbles inside the cylinder and a monodomain flower state.     

High-energy 4(10)-2-fluoro-2,2-dinitroethyl and 4(10)-2,2-dinitropropyl derivatives of polynitrohexaazaisowurtzitanes

Russian Chemical Bulletin - Methods for the syntheses of a series of high-energy 4(10)-2-fluoro-2,2-dinitroethyl and 4(10)-2,2-dinitroethyl derivatives of polynitrohexaazaisowurtzitanes were...     

Synthesis of high energy nitroguanidine derivatives

Russian Chemical Bulletin - New energy-rich derivatives of 2-nitroguanidine were obtained. The synthesis was based on the reaction of 1-chloromethyl-2-nitroguanidine, which was obtained by...     

Synthesis of polyoxymethylene derivatives of 1-oxytriaz-1-ene 2-oxides as the novel promising donors of nitric oxide in the living organisms

Russian Chemical Bulletin - Novel both symmetric and asymmetric polyoxymethylene derivatives of bis(oxytriazene N-oxides) were synthesized by the nucleophilic substitution of bis(chloromethyl)...     

Synthesis of 6,7-Dihydroindazole and 7,8-Dihydroquinazoline Derivatives from Ethyl 4,4-Dimethyl-9-oxo-3,4-dihydro-9H-xanthene-2-carboxylates

Russian Journal of General Chemistry - A procedure has been developed for the synthesis of 6,7-dihydroindazoles and 7,8-dihydroquinazolines by reaction of 3,4-dihydroxanthone derivatives with 1,2-...     

A novel type of incommensurate phase in quartz: The elongated-triangle phase

We present evidence for a thermodynamically stable incommensurate elongated-triangle (ELT) phase in quartz, observed by transmission electron microscopy at the α-β structural transition. The phase sequence on cooling is: incommensurate equilateral-triangle (EQT) phase (ferroelectric)—incommensurate ELT (ferroelectric and ferroelastic)— uniform α phase. The ELT blocks could be responsible for the large light scattering in the vicinity of the α-gb transition. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 376–381 (10 September 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Structure and parameters of the shock layer formed when a supersonic underexpanded jet interacts with a counterpropagating hypersonic flow in the transition regime

The method of molecular dynamics (the Bird system) has been used to mathematically model a planar, strongly underexpanded supersonic jet that encounters a hypersonic flow of rarefied gas. Particular attention is paid to the structure and parameters of the shock layer close to the plane of symmetry. The results of calculations are presented for currents of a monatomic gas, simulating argon, with a Mach number of the external flow of M_∞=5.48, a Mach number at the nozzle edge of M_a=1, a ratio of the density at the nozzle edge to the density of the unperturbed flow equal to 130, and various stagnation temperatures of the external flow and of the jet. The evolution of the structure and the parameters of the shock layer as the Knudsen number Kn_∞ varies from 0.02 to 0.35 is considered. The results are compared with the data calculated for the shock layer when argon flows around thermally insulated cylinders. The main features and regularities of the relaxation of the translational degrees of freedom of the gas for external and jet flows are considered. Data are presented on the form of the distribution function over velocities and its evolution as gas moves through the shock layers. Zh. Tekh. Fiz. 68, 13–18 (July 1998)     

Energy features of an adiabatically loaded anharmonic oscillator

An excited anharmonic oscillator is considered under conditions of adiabatic (i.e., slow, as compared to the oscillation period) loading with an external force tending to a constant value at long times. The energy characteristics of the adiabatically loaded anharmonic oscillator, such as the instantaneous energy of the oscillator, the maximum kinetic (oscillation) energy, and the kinetic and potential energies averaged over the period, are analytically calculated as a function of the steady-state force. The analytical results are confirmed by the data of numerical calculations. It is established that the external force gives rise to a redistribution of the average kinetic and potential components of the initial energy of the anharmonic oscillator and that the transferred energy portions at a small external force considerably exceed the average work done by the external force.     

Finite volume schemes for multi-dimensional hyperbolic systems based on the use of bicharacteristics

In this paper we present recent results for the bicharacteristic based finite volume schemes, the so-called finite volume evolution Galerkin (FVEG) schemes. These methods were proposed to solve multi-dimensional hyperbolic conservation laws. They combine the usually conflicting design objectives of using the conservation form and following the characteristics, or bicharacteristics. This is realized by combining the finite volume formulation with approximate evolution operators, which use bicharacteristics of the multi-dimensional hyperbolic system. In this way all of the infinitely many directions of wave propagation are taken into account. The main goal of this paper is to present a self-contained overview on the recent results. We study the L ¹-stability of the finite volume schemes obtained by various approximations of the flux integrals. Several numerical experiments presented in the last section confirm robustness and correct multi-dimensional behaviour of the FVEG methods. This research has been supported under the VW-Stiftung grant I 76 859, by the grant No 201/03 0570 of the Grant Agency of the Czech Republic, by the Deutsche Forschungsgemeinschaft grant GK 431 and partially by the European network HYKE, funded by the EC as contract HPRN-CT-2002-00282.