A slow wave free-electron laser

A simple calculation of a free-electron laser in the Compton regime that uses a dielectric-lined waveguide is presented. The introduction of a dielectric lining in a free-electron laser considerably reduces the requirements on beam voltage for generating a given frequency ω₁=k₀c/(1 - v_b η/c), where k₀ is the wiggler wave period η is the effective index of refraction (1<η<√ϵ) and ϵ is the permittivity. The system supports electromagnetic waves whose Poynting flux is largely concentrated in the dielectric; hence the electron beam is required to propagate close to the dielectric lining. The mode structure and dispersion behavior of the guiding system without the beam are discussed. a thin annular beam is introduced, and a perturbation theory is used to obtain the frequency and growth rate of radiation     

Photo and electroluminescence properties in Zns: (Cu,La) and Zns: (Ag,La) phosphors

A method for preparation of ZnS: (Cu, La) and ZnS: (Ag, La) phosphors is described. Photo and electroluminescence of these phosphors have been studied. The voltage and frequency variation of EL brightness have also been reported. The results agree with the collision-excitation mechanism in the Schottky barrier. The emission of blue, green and yellow bands has been interpreted in terms of different electronic transitions. Simultaneous action of both the field and the 3650 Å radiation has been studied. An attempt has also been made to explain the quenching and enhancement.     

An algorithm for reducing storage requirements in computer calculation of chemical equilibria

An algorithm for storage of stoichiometric coefficients of the possible complexes and solids in a multi-component system of metals and ligands is described, along with FORTRAN code for its implementation. The proposed algorithm results in considerable saving in storage over the conventional use of a two-dimensional array. The saving in storage is especially useful for microcomputers, and for very large problems such as those encountered in geochemical calculations.     

Magnetic fluid based squeeze film between porous annular curved plates with the effect of rotational inertia

The squeeze film behaviour between rotating annular plates was analysed theoretically when the curved upper plate with a uniform porous facing approached the impermeable and flat lower plate, considering a magnetic fluid lubricant in the presence of an external magnetic field oblique to the plates. Expressions were obtained for pressure and load capacity; and response time is given by a differential equation. The increases in pressure and load capacity depended only on the magnetization. However, the increase in response time depended on magnetization, fluid inertia and speed of rotation of the plates.     

Fourier transform infrared spectral study of N,N′-dimethylformamide-water-rhodamine 6G mixture

Infrared absorption spectra of N,N′-dimethyl formamide in the absence and presence of water, rhodamine 6G and water–rhodamine 6G mixture are reported. Assignment of observed bands has been made on the basis of density functional theory calculations and available assignments in the literature. Certain bands show changes in their positions and intensities when water is added to N,N′-dimethylformamide. This is due to hydrogen bonding interaction between these molecules. Similar changes are also observed for dimethylformamide and Rh6G mixture to a lesser extent. The presence of Rh6G in a dimethylformamide–water mixture reverses these spectral changes due to preferential solvation of Cl^? by water molecules. Solvation reduces or nullifies the hydrogen bonding between dimethylformamide and water in the mixture.     

Estimation of 90Sr in reprocessing streams using pre-packed extraction chromatographic column of 4,4'(5')-bis(tert-butylcyclohexano)-18-crown-6 impregnated on amberlite XAD-7

This work focuses on the polymorphic nature of the UO₃ and UO₃–H₂O system, which are important materials associated with the nuclear fuel cycle. The UO₃–water system is complex and has not been fully characterized, even though these species are key fuel cycle materials. Powder X-ray diffraction, and Raman and fluorescence spectroscopies were used to characterize both the several polymorphic forms of UO₃ and the certain UO₃-hydrolysis products for the purpose of developing predictive capabilities and estimating process history; for example, polymorphic phases of unknown origin. Specifically, we have investigated three industrially relevant production pathways of UO₃ and discovered a previously unknown low temperature route to the production of β-UO₃. Several phases of UO₃, its hydrolysis products, and key starting materials were synthesized and characterized as pure materials to establish optical spectroscopic signatures for these compounds for forensic analysis.