Identification of mechanical properties of inhomogeneous materials

In the present paper, the stress-strain state of tubes made of inhomogeneous elastic materials is considered. We discuss what causes the onset of inhomogeneity and solve a problem for a tube consisting of an inhomogeneous and a homogeneous layer. It is shown how the variations in the thickness ratio of the homogeneous and inhomogeneous material layers affect the values of the longitudinal and circular deformations on the external surface of the tube under the action of constant internal pressure; it is noted that this effect can be used to monitor the pipeline state and to ensure its safe operation. A method for identifying mechanical properties of deformable inhomogeneous materials is proposed; this method is based on the use of thick-walled tubular specimens in calibration tests, which is especially convenient when analyzing the action of aggressive media or radiation on the properties of deformable materials.     

10 ps High Power Laser System at 248 nm

A simple 10 ps KrF laser system consisting of quenched dye laser oscillator pumped by a XeCl laser, a distributed feedback dye laser (DFDL), a three-stage dye amplifier and a two-stage KrF amplifier are described. The output of the laser system is 140 mJ with 10 ps pulse width by using polarization-multiplexing amplification. A focused output laser intensity of about 4×1015 W/cm2 is obtained. The saturation fluence for KrF laser is obtained with this laser.     

Condensation of monosilane-argon and monosilane-helium mixtures in free jets

Condensation of gaseous monosilane-argon and monosilane-helium mixtures was investigated in free jets by a Rayleigh scattering laser diagnostic technique. The condensation of a SiH₄-Ar mixture begins to develop at a lower stagnation pressure and at a shorter distance from the nozzle, and proceeds at a higher rate, as compared to condensation in monosilane-helium and pure argon jets. The results of Rayleigh scattering measurements in condensing monosilane-argon jets scale with the parameter P ₀ d ^0.8. An analysis of the results obtained in this study and found in literature suggests that simultaneous monosilane-argon condensation lead-ing to the formation of mixed clusters takes place in the monosilane-argon mixture.     

Radial angular temperature distributions for nonisothermal two-phase filtration of oil and water

The distributions of phase saturations, pressure, and temperature in a porous medium of nonuniform permeability are studied by numerical modeling of nonisothermal two-phase filtration of oil and water with the Joule-Thomson effect and adiabatic effect taken into account. It is shown that the presence of nonuniformity in the near-well zone of the reservoir results in nonmonotonic angular and radial distributions of temperature and phase saturations. During oil and water filtration, there is transition from negative to positive temperature anomalies or vice versa, depending on the ratio of the reservoir permeabilities and the presence of a segment on which the angular temperature distribution in the well is nonuniform. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 124–130, November–December, 2008.     

Analysis of Raman spectra of amorphous-nanocrystalline silicon films

A new method is proposed for the treatment of Raman spectra of amorphous-nanocrystalline silicon films serving as a major component in solar cells. The method is based on the well-known theory of strong spatial localization (confinement) of phonons and offers the possibility of estimating the fractional content of the amorphous and crystalline phases in a film and the size distribution of nanocrystals.     

Stimulated Smith-Purcell radiation

JETP Letters - The design of free-electron lasers (FELs) based on submillimeter-range undulators involves difficulties associated with the fabrication of undulators with a very small period. To do...     

A GROUP OF EXACT (3+1) DIMENSIONAL CYLINDRICALLY SYMMETRIC WAVE SOLUTIONS TO THE EINSTEIN GRAVITATIONAL FIELD EQUATION

Starting with the diagonal spacetime metric tensor, the Einstein gravitational field equation is solved, and a set of exact (3+1) dimensional cylindrically symmetric wave solutions with two arbitrary functions are found. In these solutions all nonvanishing components of spacetime metric tensor are varying with the same propagating factor (ct-z) while the waves are travelling along z axis. The physical picture and the condition of positive energy density of the wave solutions are discussed.     

Orthogonality Relations for a Stationary Flow of an Ideal Fluid

For a real solution (u, p) to the Euler stationary equations for an ideal fluid, we derive an infinite series of the orthogonality relations that equate some linear combinations of mth degree integral momenta of the functions u_iu_j and p to zero (m = 0, 1,... ). In particular, the zeroth degree orthogonality relations state that the components ui of the velocity field are L²-orthogonal to each other and have coincident L²-norms. Orthogonality relations of degree m are valid for a solution belonging to a weighted Sobolev space with the weight depending on m.     

La2NiO4／Al2O3催化剂上CH4／CO2的重整

 通过溶胶－凝胶方法制备了尖晶石结构的La2NiO4／Al2O3催化剂，采用BET，XRD和TG表征了催化剂的孔分布、比表面积、体相组成以及凝胶样品的热失重和热分解过程．将催化剂应用于CH4／CO2重整反应制合成气，考察了惰性气体和反应温度对转化率、选择性以及积碳的影响．结果表明，在高空速（GHSV＝4．8×104ml／（g·h））下，CH4和CO2转化率分别为51％和60％，CO和H2的选择性约为98％和92％，惰性气体He的引入明显地提高了CH4和CO2的转化率．     

Dirichlet to Neumann operator on differential forms

We define the Dirichlet to Neumann operator on exterior differential forms for a compact Riemannian manifold with boundary and prove that the real additive cohomology structure of the manifold is determined by the DN operator. In particular, an explicit formula is obtained which expresses Betti numbers of the manifold through the DN operator. We express also the Hilbert transform through the DN map. The Hilbert transform connects boundary traces of conjugate co-closed forms.