Some features of the buckling of stringer shells

A technique for stability analysis of stringer shells is proposed. It is used to analyze the minimum critical stresses. The dependence of the dimensionless parameters σ_cr/σ_cl on the number of stringers is plotted. The linear and nonlinear theories of ribbed shells are used to examine the features of how stringer shells lose stability. It is shown that the minimum critical stresses determined using the theory of ribbed shells and a structurally orthotropic model are close within the range of stiffness parameters considered __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 2, pp. 59–64, February 2006.     

Theory of g-factor enhancement in narrow-gap quantum well heterostructures

We report on the study of the exchange enhancement of the g-factor in the two-dimensional (2D) electron gas in n-type narrow-gap semiconductor heterostructures. Our approach is based on the eight-band k?p Hamiltonian and takes into account the band nonparabolicity, the lattice deformation, the spin-orbit coupling and the Landau level broadening in the δ-correlated random potential model. Using the 'screened' Hartree-Fock approximation we demonstrate that the exchange g-factor enhancement not only shows maxima at odd values of Landau level filling factors but, due to the conduction band nonparabolicity, persists at even filling factor values as well. The magnitude of the exchange enhancement, the amplitude and the shape of the g-factor oscillations are determined by both the screening of the electron-electron interaction and the Landau level width. The 'enhanced' g-factor values calculated for the 2D electron gas in InAs/AlSb quantum well heterostructures are compared with our earlier experimental data and with those obtained by Mendez et?al (1993 Phys.?Rev.?B 47 13937) in magnetic fields up to 30?T.     

Stability of ribbed cylindrical shells with a nonideal shape

A finite-difference method was proposed and used for analysis of critical loads of shells that have initial imperfections of different types, both regular and local. Ribbed shells were analyzed with allowance for the discreteness in the arrangement of the ribs. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 35, No. 12, pp. 33–39, December, 1999.     

X-ray-line plasma satellites of ions in solid target plasmas produced by picosecond laser pulse

The X-ray lines of ions in a solid target interacting with picosecond laser pulses of moderate intensity (2×10¹⁷ W/cm²) were measured on the “Neodim” laser facility. X-ray Ly _α emission spectra of hydrogen-like fluorine ions were observed. Satellite lines were also observed, evidencing the presence of intense plasma oscillations. The positions and separation between the satellites allow their assignment to the intense electrostatic oscillations with an amplitude larger than 10⁸ V/cm and a frequency of about 7× 10¹⁴ s^?1 that is noticeably lower than the laser frequency ω_las～1.8×10¹⁵ s^?1. It is suggested that these oscillations may be due to strong plasma turbulence caused by the development of plasma oscillations of the Bernstein-mode type under the action of a strong magnetic field generated in plasma. The experimental results are compared with the calculated spectra of multicharged ions.     

Vibrational spectra and structure of caprolactamates of group II metals

Differences between the IR and Raman spectra of the dicaprolactamates of Mg, Ca, and Ba indicate differences in their structures. Barium dicaprolactamate has an ionic structure, while the dicaprolactamates of Mg and Ca are partially covalent and have one-dimensional chain structures with various types of NCO group (terminal, bridge). In solution the dicaprolactamates of Mg and Ca are associated on account of the formation of bridged NCO groups. It was shown that the vibration frequencies of the bridged NCO groups lie in the range 1580–1620 cm^–1, and those of the terminal groups in the range 1550–1580 cm^–1.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1570–1573, July, 1990.     

Stability of nonideal ribbed spherical bands

Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Prikladnaya Mekhanika, Vol. 26, No. 8, pp. 43–46, August, 1990.     

Transformation of the Angular Power Spectrum of Scattered Radiation in a Turbulent Absorbing Magnetoactive Plasma

We consider the oblique incidence of a small-amplitude plane electromagnetic wave on a layer of turbulent absorbing plasma in a uniform external magnetic field. The equations for the first two statistical moments of the angular power spectrum of scattered radiation are derived in the geometrical-optics approximation. We show that two asymmetry factors of the problem, i.e., the oblique incidence and the influence of the anisotropic medium, compensate for each other along a certain direction and impede the appearance of the effect of displacement of the power-spectrum maximum and the effect of anomalous spectrum broadening. We find the condition at which such a case of wave propagation is realized. The dependence of the angular-spectrum shape on the distance from the plasma-layer boundary is studied numerically without using the small-angle approximation. The calculations confirm the results obtained using the geometrical-optics approximation.     

Sorption and Separation of Optical Isomers of 2-Butanol by Chiral Porous Coordination Polymers

Theoretical and Experimental Chemistry - It was shown that porous coordination polymers (PCPs) of 3d metals containing chiral centers in fragments of deprotonated (S)-lactic and (R)-aspartic acid...