Finite difference analysis of torsional vibrations of pretwisted,rotating, cantilever beams with effects of warping

Theoretical natural frequencies of the first three modes of torsional vibration of pre-twisted, rotating cantilever beams are determined for various thickness and aspect ratios. Conclusions concerning individual and collective effects of warping, pretwist, tension-torsion coupling and tennis racket effect (twist-rotational coupling) terms on the natural frequencies are drawn from numerical results obtained by using a finite difference procedure with first order central differences. The relative importance of structural warping, inertial warping, pretwist, tension-torsion and twist-rotational coupling terms is discussed for various rotational speeds. The accuracy of results obtained by using the finite difference approach is verified by a comparison with the exact solution for specialized simple cases of the equation of motion used in this paper.     

Effect of driving laser intensity fluctuations on optical bistability of a system with large permanent-dipole molecules

The statistical properties of an optical bistable system consisting of two-level atoms with large permanent dipole moments contained in a Fabry-Perot cavity are investigated assuming the external laser intensity fluctuations to be the main source of noise. The probability transformation rule is applied to obtain the probability distribution for the transmitted intensity whereas the probability distribution for the incident intensity is assumed to be that of the partially coherent laser light. It turns out that in the optical bistability region two values of fluctuation parameters are possible for a given value of input intensity, which produces interesting hysteresis effects.     

Development of a terminal voltage stabilization system for the FOTIA at BARC

A terminal voltage stabilization system for the folded tandem ion accelerator (FOTIA) was developed and is in continuous use. The system achieves good voltage stabilization, eliminates ground loops and noise interference. It incorporates a correcting circuit for compensating the mains frequency variations in the GVM amplifier circuit. The present system has two modes of operation namely GVM control mode and slit control mode. A voltage stability of about ± 2 kV has been achieved. In this paper, some of the salient features of the voltage stabilization system are discussed.     

Crystalline constituents from euphorbiaceae—XIII : The structure of a new triterpene from Euphorbia nerifolia L.

From the leaves and stems of Euphorbia nerifolia Linn., a new triterpene was isolated besides friedelan-3α- andβ-ols, and taraxerol. From a study of its chemical reactions and spectral data, the new triterpene was shown to be glut-5(10)-en-1-one(3).     

Thermal expansion of irradiated polytetrafluoroethylene

The thermal expansion coefficient of gamma-irradiated Polytetrafluoroethylene (PTFE) has been measured in the temperature range 80–340 K by using a three-terminal capacitance technique. The samples are irradiated in air at room temperature with gamma rays from a Co⁶⁰ source at a dose rate of 0.26 Mrad/h. The change in crystallinity is measured by an x-ray technique. The expansion coefficient is found to increase with radiation dose below 140 K owing to the predominant effect of degradation. Above 140 K, the expansion coefficient is found to decrease with radiation dose because of the enhanced crystallinity. The temperatures of the two first-order phase transitions are also found to shift to lower temperatures owing to degradation of PTFE.     

Nitrileketenimine tautomerism in substituted alkylidene malononitriles and alkylidene cyanoacetates: A characteristic UV absorption band

Several alkylidene malononitriles (1b,1d,1e,2b and4b) and alkylidene cyanoacetates (1a,2a and4a) studied exhibit a long wavelength UV absorption band around 355 nm which shows a hyperchromic effect in the presence of ethanolic alkali. This band has been assigned to the ketenimine tautomer (5). Addition of water to1b,1e and2b gives the corresponding pyridine diols (7a,7b and8a) respectively. Similarly, addition of ethanol to1e and2b gave the corresponding ethoxypyridine derivatives (7c and8b). Mechanism of formation of these compounds is discussed. Structures, as well as mechanism of formation of1c,7c and10 obtained from1b,1e and2b respectively on standing at room temperature are also discussed.     

Cauchy sequences in quasi-pseudo-metric spaces

This paper considers the problem of defining Cauchy sequence and completeness in quasi-pseudo-metric spaces. The definitions proposed allow versions of such classical theorems as the Baire Category Theorem, the Contraction Principle and Cantor's characterization of completeness to be formulated in the quasi-pseudo-metric setting.     

Third order voltage mode universal filter using CCCII

This paper brings a multi input single output third order universal filter using second generation current controlled current conveyor (CCCII). The proposed structure consists of three CCCIIs and three capacitors for all filter responses. The universal filter offers all five sections of filter responses, namely: low-pass, high-pass, band-pass, notch filter and all-pass. The topology can provide all filter responses by the proper selection of input. The proposed universal filter offers some important features like no external resistor, minimum number of CCCIIs, no component matching constraint for filter response, electronically adjustable filter response using bias current of CCCIIs and many more. The workability of the proposed structure is well verified with PSPICE in which simulation results follow the theoretical one.     

A Low Power Minimal Error IEEE 802.15.4 Transceiver for Heart Monitoring in IoT Applications

Wireless Personal Communications - With the advancement of communication technologies, the number of devices connected to the internet is increasing exponentially day by day. Multiple IoT...