Study of phase transition and volume thermal expansion in a rare-earth (RE) oxyfluoride system by high-temperature XRD (RE=La, Nd, Sm, Eu and Gd)

Volume thermal expansion behaviour of a number of rare-earth oxyfluorides (REOF) have been studied using high-temperature X-Ray diffractometry (HT-XRD) in the 298–1075 K range in air. The studies revealed an anomalous expansion for each compound associated with phase transition. The phase transition temperature and the coefficient of volume thermal expansion of five compounds in REOF series determined by this method are reported and compared with our earlier results obtained by dilatometry.     

Electrical and Dielectric Characteristics of BiSmO3

Physics of the Solid State - The synthesis of the perovskites BiSmO3 was done by the solid-state reaction method. In this communication, the structural and detailed electrical (dielectric,...     

ChemInform Abstract: Study of Phase Transformation in BaTe2O6 by in situ High‐Pressure X‐Ray Diffraction,Raman Spectroscopy,and First‐Principles Calculations.

The title compound is synthesized by solid state reaction of a stoichiometric mixture of BaCO₃ and TeO₂ (air, 550 °C for 6 h, and 650 °C for 12 h).     

A coupled zigzag theory for the dynamics of piezoelectric hybrid cross-ply plates

A recently developed coupled third-order zigzag theory for the statics of piezoelectric hybrid cross-ply plates is extended to dynamics. The theory combines a third-order zigzag approximation for the in-plane displacements and a sub-layerwise linear approximation for the electric potential, considering all components of the electric field. The nonuniform variation of the transverse displacement due to the piezoelectric field is accounted for. The conditions for the absence of shear traction at the top and bottom surfaces and continuity of transverse shear stresses in the presence of electromechanical loading are satisfied exactly, thereby reducing the number of displacement variables to five, which is the same as in a first- or third-order equivalent single-layer theory. The governing equations of motion are derived from the extended Hamilton's principle. The theory is assessed by comparing the Navier solutions for the free and forced harmonic vibration response of simply supported plates with the exact three-dimensional piezoelasticity solutions. Comparisons for hybrid test, composite and sandwich plates establish that the present theory is quite accurate for the dynamic response of moderately thick plates.     

Cation disorder and structural studies on Bi4−x Nd x Ti3O12 (0.0≤x≤2.0)

Here we report the results of combined powder X-ray and neutron diffraction studies of Bi_4?x Nd _x Ti₃O₁₂ (0.0 ≤ x ≤ 2.0) compositions. The parent Bi₄Ti₃O₁₂ has an orthorhombic lattice (space group: B2cb) with unit cell parameters a = 5.4432(5) Å, b = 5.4099(5) Å and c = 32.821(2) Å, and V = 966.5(1) ų. This orthorhombic lattice is retained in all the studied compositions. The unit cell parameters gradually decrease with Nd³⁺ ion concentration with a discontinuity at x = 0.75. Orthorhombicity of the lattice decreases with increase in Nd³⁺ content in the lattice. The orthorhombic unit cell parameters for a representative Bi₂Nd₂Ti₃O₁₂ composition are: a = 5.3834(9), b = 5.3846(9) and c = 32.784(1) Å. The observed orthorhombic distortion at x = 2.0 is very small and thus the crystal structure apparently has a pseudo-tetragonal lattice. In addition, Nd³⁺ preferentially substitutes in the perovskite slab of the Aurivillius structure. The fraction of Nd³⁺ in the fluorite slab increases with increase in Nd³⁺ contents.     

关于Hirota-Satsuma系统初值问题的局部和整体适定性

本文利用ＫＤＶ方程所对应的线性方程解所具有的光滑效应及压缩映像原理,得到了Ｈｉｒｏｔａ－Ｓａｔｓｕｍａ系统初值问题的局部和整体适定性结果．     

Overlapping B3Π0u ← X1Σ g/+ and 1Π1u ← X1Σ g/+ non-radiative characteristic of Br2 vapour in the wavelength region 505–541 nm

The vibronic vapour phase photoacoustic spectrum of Br₂ in the wavelength region 505–541 nm (19796–18480 cm⁻¹) has been recorded using microphone as well as pump-probe method. Discrete vibronic bands superimposed on a monotonically increasing continuum background towards the dissociation limit results from the overlapping B ³Π _0u ^/+ ← X ¹Σ _g ^/+ and ¹Π_1u ← X ¹Σ _g ^/+ electronic transitions. Vibronic bands originating from υ″=0 have been used to estimate the relative rate of non-radiative relaxation as a function of the excited state B ³Π_0u vibrational quantum number υ′. A comparison with the optical absorption spectroscopy of Br₂ leads to the identification of three broad spectral regions between 505 and 541 nm (19796 and 18480 cm⁻¹) on the basis of different non-radiative relaxation processes.     

On Approximating Lead Time Demand Distributions Using the Generalised λ-type Distribution

In this paper the use of the generalised λ-type distribution (GLD) is proposed for the analysis of standard inventory problems. Using this distribution to approximate the lead time demand distribution we analyse the generalised newsboy problem and a (Q, r) policy. The standard inventory measures like optimal order size, reorder level, average demand lost, etc. are obtained under the GLD and are compared with those given by Shore's approximation and also under exact distributional assumptions. Through a numerical study the various inventory measures are compared using the GLD and Shore's approximation with the exact distributions. The comparison reveals that the GLD approximation is better suited than Shore's approximation to model the lead time demand.     

Electrochemical preparation of orthophenylenediamine on different cathodes in sulfuric acid

The electrochemical reduction of nitro group of orthonitroaniline (ONA) is carried out on Pb, Cu, and Sn electrodes. The effect of current density, temperature, and acid concentration on product yield is studied. The polarization curve for ONA in acidic condition is recorded. Under preparative electrolysis, ONA gives a mixture of hydroxylamine and phenylenediamine, the proportion of phenylenediamine increasing with the electrolysis time. The product formation is confirmed by thin-layer chromatography, melting-point test, UV-visible, IR, and NMR methods. The operating conditions are optimized for a good yield of orthophenylenediamine. The catalytic activity of different metals for the reduction of nitro group is discussed. The percent yield of orthophenylenediamine is found to be high on the lead electrode. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 2, pp. 215–221. The text was submitted by the authors in English.