Shock response of viscoelastically damped sandwich plates

Analysis for the transient response of a simply supported three layer viscoelastically damped sandwich plate, subjected to a half sine shock pulse, has been carried out, with account taken of the transverse inertia effects only. The properties of the viscoelastic core material have been represented by those of a four element viscoelastic model. The influences of the variation of various geometrical and physical parameters of the damped sandwich plate on the shock response are investigated. The decay rate of the transverse vibrations of the plate is evaluated in terms of the logarithmic decrement.     

Correlation of light beams scattered at different angles by a ground glass

A quantitative study of the contrast of Young's fringes obtained with a fully scattering element by double exposure technique as a function of the inclination of the incident beam and the effect of varying the scatterer- photographic plate distance upon the γ - θ curve have been presented.     

Using fatigue information in design

It is impossible to find, for a specific design concern, fatigue information that is entirely adequate for an exact quantitative evaluation. Some of the approaches available for approximate design estimates are described to illustrate the problems that may occur and the considerations important in using available fatigue information in design.     

Magnetic phase diagram of anisotropic layered superconductors via magnetization measurements forH‖c in Bi2212

The Bi₂Sr₂CaCu₂O₈ system is viewed as an archetypal of superconductors modelled as Josephson coupled CuO₂ bilayers. The isothermal and temperature dependent DC and AC magnetization measurements forH‖c in a single crystal of Bi2212 have been performed. Qualitative changes are observed to occur over a narrow range of temperature values before reaching the superconducting-normal transition. The observed behaviour can be ascribed to the rapid variation in the strength of the coupling between the superconducting CuO₂ planes (i.e., bilayers in the case of Bi2212). Strongly coupled planes behave like a 3D superconductor, whereas weakly coupled planes have a two component response attributable to 2D planes and interplanar couplings. We believe that this paper is a plethora of new findings. Our observations imply that resistivity across the planes becomes zero earlier than that within the planes. A new line (designated asH _2D(T)) above which the change in the electromagnetic response is dominated by quasi 2D-planes has been determined for the first time. This paper also contains the first observation of Differential Diamagnetic Effect (DDE) in the In-phase AC susceptibility data which signals the onset (atT _2D(H)) of dominance of response from 2D-planes. In addition to a host of interesting thermomagnetic history effects which are a consequence of interplay between the diamagnetic responses from the two components, a comparison of irreversibility lines (of the 3D state) determined by different methods on the same specimen of a HTSC is also being presented for the first time. We have come across Paramagnetic Meissner Effect (PME), first recognized in ceramic samples of Bi2212, in the temperature region of dimensional crossover in our single crystal sample, whichinter-alia confirms our labelling of the two component behaviour. A schematic phase diagram summarizing the various transformations that can occur nearT _c in the electromagnetic response of an anisotropic layered system has been drawn.     

151Eu Mössbauer studies in the high Tc superconducting oxide materials

¹⁵¹Eu Mössbauer studies have been made across the respective superconductive transition temperatures in two compounds, La_1.7Eu_0.1Sr_0.2CuO_4?y and EuBa₂Cu₃O₇, having zero resistance state at 25K and 85K respectively. The¹⁵¹Eu isomer shift data establish that Eu ions are in trivalent state at all temperatures. The Mössbauer f-factor does not show any significant anomaly across the T_C.     

Electrochemical transacylations: A mild synthesis of esters

Esters can be synthesized by electrochemically oxidizing hydroquinone carboxylates in the presence of alcohols. High yields are obtained in acidic or basic solutions and at low temperatures.     

Melting of lead and zinc to 60 kbar

The melting curves for lead and zinc were determined to 60 kbar. Our melting data for lead is in good agreement with that of Millet up to 22 kbar, beyond which Millet's values are significantly higher than ours. The melting curve for zinc is almost linear to 60 kbar and our values are lower than the values reported by other workers. The melting relationship proposed by Kennedy as well as the Lindemann law have been examined in the light of the new melting data for these two metals. A straight line can be fitted through the T_m vs ΔV/V₀ plots for zinc within the limits of experimental precision, but the data for lead shows a departure from the straight line fit. The lead melting curve is concave toward the T_m axis, as predicted by the Lindermann law and, in this respect, resembles previously studied Van der Waals solids.     

Anomalous behaviour of hyperfine fields at iron in new magnetic systems RuxFey Si and RuFeB

A new class of magnetic system Ru_xFe_ySi, has been identified in which the hyperfine field at Fe, as sensed by⁵⁷Fe Mossbauer effect, is seen to evolve at a characteristic temperature far below the bulk magnetic ordering temperatures.     

RuFeSi — A new magnetic system

A ternary system consisting of Ru, Fe and Si is identified in which the hyperfine field at Fe is seen to evolve at a characteristic temperature, T¹, far below the magnetic ordering temperature, T_m. It is speculated that the magnetic ordering at T_m is itinerant and T¹ corresponds to the localization of the majority spin electrons at the Fe atoms.