FeCl3-Catalyzed Pechmann Synthesis of Coumarins in Ionic Liquids

The synthesis of coumarin derivatives via Pechmann reaction using anhydrous FeCl₃ as Lewis acid catalyst in ionic liquid medium has been carried out. The best results were obtained (yields as high as 89%) with ionic liquids having bis(triflic)imide as a counteranion. The ionic liquid could easily be recovered and reused.     

Effect of thermal gradient on frequencies of an orthotropic rectangular plate whose thickness varies in two directions

A simple model is presented for the use of research workers in space technology, mechanical sciences and nuclear energy where certain components of the structures have to operate under elevated temperatures. The effect of a constant thermal gradient on the free vibrations of an orthotropic rectangular plate whose thickness varies linearly in two directions is considered. An approximate but quite convenient frequency equation is derived by using Rayleigh-Ritz techniques with a two-term deflection function. The upper bound on the frequency corresponding to the first mode of vibrations is obtained for various boundary conditions, and for various values of the length to width ratio, two paper constants and the temperature gradient.     

Plasmonic enhancement of optical absorption of UV radiation by Au nanoparticles dispersed on ZnO thin film

Ultraviolet photoconductivity in sol gel-derived ZnO thin film loaded with gold (Au) nanoparticle (NPs) is investigated. Au-NPs loaded ZnO thin film (Au-NPs/ZnO) is found to exhibit high photoconducting gain (K) of about 4.12 × 10³ as compared to the bare ZnO thin film-based photodetector (4.9 × 10¹). The enhanced photoconductive gain of Au-NPs/ZnO detector has been achieved due to simultaneous lowering of dark current which occurs due to Schottky barrier effect originated after dispersing the Au NPs on the surface of ZnO thin film. The enhancement in photocurrent upon UV illumination is due to trapping of UV radiation via plasmonic effect caused by Au-NPs and subsequently coupling of absorbed light with the optical modes of underlying semiconducting ZnO surface.     

Dispersion data for open inverted microstrip on RT-duroid and fused quartz substrates

Accurate dispersion data for open inverted microstrip is presented. Two most commonly used substrate materials, namely, RT-duroid (dielectric constant 2.22) and fused quartz (dielectric constant 3.78) are considered. The work is a continuation of the earlier reported data on a similar structure, called suspended microstrip, and will be an useful addition to the millimeter-wave designer's library.     

Natural frequencies of a non homogeneous isotropic elastic infinite plate of variable thickness resting on elastic foundation

Summary The dynamic free response of a nonhomogeneous isotropic elastic infinite plate of parabolically varying thickness resting on an elastic foundation has been studied. The frequencies, deflections and moments corresponding to the first five modes of vibration have been computed for the two combinations of boundary conditions, clamped-clamped (C-C) and clamped-simply supported (C-SS) and various values of taper constant, nonhomogeneity parameter and foundation modulus by applying the method of Frobenius for the solution of the governing differential equation of motion.

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Sommario Si sono studiate le oscillazioni libere di una piastra elastica infinita, non omogenea, isotropa, di spessore parabolicamente variabile, poggiata su un suolo elastico. Applicando il metodo di Frobenius per la soluzione della equazione differenziale del moto si sono calcolate le frequenze, le deformate ed i momenti corrispondenti ai primi cinque modi di vibrazione per due combinazioni di condizioni al contorno, incastro-incastro ed incastro-appoggio e diversi valori della rastremazione, del parametro di non omogeneità e del modulo del suolo.

     

Free vibrations of an isotropic nonhomogeneous infinite plate of linearly varying thickness

Summary The free transverse vibrations of an isotropic nonhomogeneous infinite plate of variable thickness have been studied on the basis of classical plate theory. The governing differential equation of motion has been solved by Frobenius method by expressing the transverse displacement as an infinite series. The frequencies corresponding to the first two modes of vibration are computed for different values of thickness variation constant, nonhomogeneity parameter, and different combinations of boundary conditions.

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Sommario Viene considerato il problema delle vibrazioni flessionali libere di una lastra infinita, isotropa, non omogenea, di spessore variabile. L'equazione del moto è stata risolta col metodo di Frobenius, esprimendo lo spostamento mediante sviluppo in serie. Sono state calcolate le prime due au to frequenze per varie combinazioni delle condizioni ai limiti e per differenti valori dei parametri caratteristici della variazione di spessore e della disomogeneità.

     

Probing electronic environment in gamma irradiated sodium borosilicate glass and simulated waste glass: a perturbed angular correlation spectroscopy study

Journal of Radioanalytical and Nuclear Chemistry - Time Differential Perturbed Angular Correlation (TDPAC) has been used to investigate the local structural changes (if any) in Sodium borosilicate...