Dielectric and optical properties of a 5-propyl-2-(<Emphasis Type="Italic">p</Emphasis>-cyanophenyl)-pyridine liquid crystal

The temperature dependences of the dielectric and optical parameters for a 5-propyl-2-(p-cyanophenyl)-pyridine (3CP) liquid crystal are investigated in the vicinity of the nematic-isotropic phase transition. The dielectric spectra of the 3CP compound in the crystalline, nematic, and isotropic phases are measured in the frequency range 1–1000 MHz, and the Debye approximations of the measured spectra are obtained. Analysis of the dependence of the static permittivity on the director orientation with respect to the direction of the electric pump field demonstrates that the angle between the dipole moment and the long axis of the molecule is approximately equal to 15°.     

Influence of cubic nonlinearity on laser radiation transmission in a photonic crystal with spatially modified media properties

The transfer matrix method was modified to explore the Kerr nonlinearity influence on laser radiation propagation in a one‐dimensional photonic crystal. The suggested spatial distribution of the refractive index allows to remove minibands and to make the transmission curve much steeper. Plain and steep photonic band gap edges are effective in creation of transmission anisotropy of powerful laser radiation. The investigated photonic crystal has a strong anisotropic optical transmission and acts as an optical analog of the electronic diode. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Stochastic radiative transfer model for mixture of discontinuous vegetation canopies

Modeling of the radiation regime of a mixture of vegetation species is a fundamental problem of the Earth's land remote sensing and climate applications. The major existing approaches, including the linear mixture model and the turbid medium (TM) mixture radiative transfer model, provide only an approximate solution to this problem. In this study, we developed the stochastic mixture radiative transfer (SMRT) model, a mathematically exact tool to evaluate radiation regime in a natural canopy with spatially varying optical properties, that is, canopy, which exhibits a structured mixture of vegetation species and gaps. The model solves for the radiation quantities, direct input to the remote sensing/climate applications: mean radiation fluxes over whole mixture and over individual species. The canopy structure is parameterized in the SMRT model in terms of two stochastic moments: the probability of finding species and the conditional pair-correlation of species. The second moment is responsible for the 3D radiation effects, namely, radiation streaming through gaps without interaction with vegetation and variation of the radiation fluxes between different species. We performed analytical and numerical analysis of the radiation effects, simulated with the SMRT model for the three cases of canopy structure: (a) non-ordered mixture of species and gaps (TM); (b) ordered mixture of species without gaps; and (c) ordered mixture of species with gaps. The analysis indicates that the variation of radiation fluxes between different species is proportional to the variation of species optical properties (leaf albedo, density of foliage, etc.) Gaps introduce significant disturbance to the radiation regime in the canopy as their optical properties constitute major contrast to those of any vegetation species. The SMRT model resolves deficiencies of the major existing mixture models: ignorance of species radiation coupling via multiple scattering of photons (the linear mixture model) or overestimation of this coupling due to neglecting spatial clumping of species (the TM approach). Thus, based on the former experience with mixture modeling, this study establishes an advanced theoretical basis for future mixture applications.     

A Study of the Dynamics of Formation of Plasmoids in the Gatchina Discharge

Technical Physics - The results of studies of the Gatchina discharge conducted at the Harbin University of Technology (China) have been presented. The Gatchina discharge is mainly used to create an...     

New binuclear <Emphasis Type="Italic">bis</Emphasis>(2,4,6,8-tetramethyl-2,4,6,8-tetraazobicyclo(3.3.0)octane-3,7-dione-<Emphasis Type="Italic">O,O</Emphasis>')-tetraaqua-hexakis(nitrato-<Emphasis Type="Italic">O,O</Emphasis>')-disamarium(III) complex: Synthesis and crystal structure

The centrosymmetric binuclear complex of samarium(III) nitrate with bicyclic biscarbamide 2,4,6,8-tetramethyl-2,4,6,8-tetraazabicyclo(3.3.0)octane-3,7-dione, or mebicar (Mk) namely, [Sm(C₈H₁₄N₄O₂)(H₂O)₂(NO₃)₃]₂ (I) has been synthesized. Its crystal structure has been characterized (CIF file CCDC no. 1451436). Crystals of complex I are triclinic, space group P1 a = 9.8661(2) Å, b = 10.2913(3) Å, c = 10.9629(3) Å, α = 74.475(2)°, β = 67.802(2)°, γ = 67.570(2)°, V = 942.68(5) ų, ρcalcd = 2.01028 g/cm³, and Z = 1. The samarium atom is coordinated by the two oxygen atoms of two Mk molecules bonded via the symmetry center, three bidentate nitrate anions, and two water molecules. The coordination number of the samarium atom is 10, the coordination polyhedron of the metal atom is a decahedron and the Sm…Sm distance is 9.7904(4) Å.     

Flow around a sphere with material cross flow at low reynolds numbers

An analytical solution is carried out for the problem of the flow around a sphere with material cross flow at Reynolds numbers less than 1 and a blowing velocity less than the free stream velocity. The method of asymptotic expansions of Pearson and Proudman is used for the solution. Expressions are obtained for the distribution of the current and velocity component functions as well as for the aerodynamic drag coefficient of the sphere. It is shown that blowing diminishes the sphere drag, where its influence will increase as the Reynolds number grows.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 103–109, May–June, 1972.     

Supersonic gas flow over a semi-infinite plate with small harmonic spanwise disturbances

The method of matched asymptotic expansions is used to investigate the problem of supersonic perfect-gas flow over a semi-infinite surface with longitudinal ribbing formed by imposing small transverse harmonic perturbations on a flat plate. The ratio of the maximum amplitude of the surface perturbations to the thickness of the boundary layer is of the order of Re^–1/4. The problem is solved with allowance for four terms of the expansion.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.1, pp. 146–156, January–February, 1993.