Optimal shock-wave systems under constraints on the total flow turning angle

A shock and subsequent rarefaction wave shock-wave system in a plane supersonic inviscid non-heat-conducting gas flow is considered. An exact analytic solution of the problem of determining the intensities of the waves leading to extreme values of the gasdynamic variables (static pressure, temperature, etc.) behind the wave is found using Lagrangian multipliers. These systems are related to the optimal ones [1, 2]. The parameters of the problem are the free-stream Mach number, the specific heat ratio, and the total flow turning angle in the wave system. Analytic solutions determining the boundaries of monotonic and nonmonotonic behavior of the gasdynamic variables behind the system are presented. The effect of the specific heat ratio on the dimensions of the domains of existence of the optimal waves is investigated.St. Petersburg. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 142–150, July–August, 1996.     

On classification of flow regimes in a channel with sudden expansion

Supersonic flows of gas in the vicinity of the bottom region known as flows with sudden expansion have been considered. On the basis of extensive experimental studies, authors have proposed a complete classification of flow regimes: stationary, oscillating, and transient. Hysteresis of the regimes change at total gas pressure increasing and decreasing in front of the nozzle has been found. Typical shock-wave configurations emerging at the jet flowing in a channel at different modes have been determined. The type of shock-wave structure and the nature of interaction of the mixing layer of a jet with the wall or reverse flow flowing into the channel from ambient medium determine the appropriate mode. Combination of physical and numerical experiment with bottom pressure calculation according to the developed semi-empirical model have revealed new flow regimes that were not studied earlier.     

X-ray determination of the mean amplitudes of vibration and debye temperatures of some rare earth monochalcogenides

The x-ray diffraction intensities of Bragg reflections have been measured at room temperature for thulium selenide, samarium sulphide, samarium selenide and samarium telluride. On the basis of a common amplitude approximation, the Debye-Waller factor, the mean amplitude of vibration and the Debye temperature have been evaluated. The values of the Debye temperatures and mean amplitudes of vibration are 176±16°K, 0·185 ± 0·017 Å (TmSe), 155 ± 7°K, 0·244 ± 0·012 Å (SmS), 153 ± 14°K, 0·221 ± 0·020 Å (SmSe) and 151 ± 20°K, 0·204 ± 0·027 Å (SmTe).     

Synthesis,structure, and luminescence properties of complex ZnLCl<Superscript>b2</Superscript> (L is 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline)

A complex ZnLCl^b2 (L is 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline) was synthesized. According to X-ray diffraction data, the Zn^p2+ ions in mononuclear molecules of the obtained complex coordinate two N atoms of the bidentate chelating ligand L and two Cl atoms. The coordination polyhedron Cl2N^b2 represents a distorted tetrahedron. In solid state at 300 K, the ligand L exhibits weak photoluminescence in the visible spectral range. The complex ZnLCl^b2 exhibits bright blue photoluminescence.     

Coherent effects in two-level amplifying and SRS-active media

Some results are reported on coherent propagation of optical pulses. In particular, a solution is presented of the Maxwell-Bloch equations for the case of amplification of high-power pulses with varying carrier frequency but with constant number of photons in the pulse.Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow. Translated from Preprint No. 211 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1988.     

Special and extreme triple shock-wave configurations

Triple shock-wave configurations in steady supersonic flows of an inviscid perfect gas are considered. Triple configurations with special intensities of shock waves and extreme ratios of various flow parameters behind these configurations are determined. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 4, pp. 39–53, July–August, 2006.     

Crystal structure of solvate [Cd2L2Cl4]·CH2Cl2 (L = pyrazolylquinoline, the derivative of monoterpenoid (+)-3-carene) and photoluminescence of chiral complex CdLCl2

Using the single crystal X-ray diffraction data (150 K, Bruker X8 Apex CCD autodiffractometer, MoK α radiation), the crystal structure of the [Cd₂L₂Cl₄]·CH₂Cl₂ (L = pyrazolylquinoline, the derivative of monoterpenoid (+)-3-carene) compound is determined. Crystals are monoclinic, unit cell parameters are: a = 10.7005(4) ?, b = 16.8491(4) ?, c = 11.9658(4) ?, β = 93.308(1)°, P2₁ space group. The structure is formed from discrete acentric molecules of a binuclear [Cd₂L₂Cl₄] complex and uncoordinated CH₂Cl₂ molecules. The Cd²⁺ ions coordinate N atoms of bidentate chelating ligands L, which leads to the closure of two five-membered chelate CdN₃C rings. The coordination sphere of Cd atoms also includes three Cl atoms (two bridging and one terminal), consequently, two CdCl₃N₂ coordination sites and a Cd₂Cl₂ metal ring are formed. The Cl₃N₂ polyhedra have the form of distorted tetragonal pyramids. The CH₂Cl₂ molecules located in the channels formed by the complexes are linked with them by weak H-bonds. The excitation spectra of L and the CdLCl₂ compound contain bands with λ_max of 352 nm and 360 nm respectively. At 300 K and λ_excit 350 nm, in the photoluminescence spectrum of L a rather intense broad split band with λ_max 372 nm and 386 nm is observed. The photoluminescence spectrum of the CdLCl₂ compound contains a broad band with λ_max 418 nm. The photoluminescence intensity of this compound is significantly lower than that of L.