http://nopr.niscair.res.in/handle/123456789/6191 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/6201 Title: Experimental and numerical realization of higher order autonomous Van der Pol-Duffing oscillator <br/> <br/>Authors: Balachandran, V; Kandiban, G <br/> <br/>Abstract: The application of the hyperchaotic dynamics will enhance the engineering system such as chaos based security of communication in information technology. Interest in such systems has been increasing. Some interesting phenomena of higher order autonomous<b style=""> </b>Van der Pol-Duffing oscillator based on fifth order hyperchaotic circuit to improve secure communication have been studied in the present paper. This circuit, which is capable of realizing the behaviour of every member of the autonomous Van der Pol-Duffing family, consists of just six linear elements (resistor, inductors and capacitors) and a smooth cubic non-linearity. In this circuit, we can confirm period doubling routes to chaos and then to hyperchaos through boundary condition, when the system parameter varies. The hyperchaotic dynamics, characterized by broad band power spectrum, is presented to confirm the hyperchaotic nature of the oscillations of the circuit. This has been investigated extensively using laboratory experiments and numerical integration of the appropriate differential equations. <br/> <br/>Page(s): 823-827 Thu, 29 Oct 2009 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/6200 Title: Novel minimum-component universal filter and quadrature oscillator with electronic tuning property based on CCCDBAs <br/> <br/>Authors: Tangsrirat, Worapong <br/> <br/>Abstract: The novel current-tunable voltage-mode universal biquad filter and sinusoidal quadrature oscillator using only two current-controlled current differencing buffered amplifiers (CCCDBAs) and two capacitors without external passive resistors have been presented. The first proposed filter realizes all the five standard types of the biquadratic functions and provides independent electronic tuning of the natural angular frequency (ω<i>_o</i>) and the bandwidth (BW) through an external bias current of the CCCDBA. No critical component matching conditions are required. The second proposed oscillator generates two sinusoidal output voltages with 90° phase difference. Its oscillation condition and the oscillation frequency (ω_o) are tunable independently through adjusting the bias current of the CCCDBA. Both the proposed circuit configurations have a low component count, attractive active and passive sensitivities and suitability to integrated circuit implementation. PSPICE simulation results that confirm the theoretical prediction, are also given and discussed. <br/> <br/>Page(s): 815-822 Thu, 29 Oct 2009 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/6199 Title: Screening current and dielectric parameters in dual QCD <br/> <br/>Authors: Nandan, Hemwati; Bezares-Roder, Nils M; Chandola, H C <br/> <br/>Abstract: The screening current mechanism and dual Meissner effect in the QCD vacuum have been studied in view of the action for a dual (magnetic) superconductor derivable from the Zwanziger’s two-potential formalism. The flux tube structure emerging as an artifact of screening current in the background of both the monopole and dyon condensation has been investigated. The magneto-statical representation of the flux tube has also been presented with the conditions which are necessary to form a tube. The dielectric parameters of dual QCD vacuum have been calculated and the size of the flux tube resulting from the monopole and dyon condensation is compared. <br/> <br/>Page(s): 808-814 Thu, 29 Oct 2009 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/6198 Title: Electronic and elastic properties of alkali-metal sulphides-Li₂S and Na₂S <br/> <br/>Authors: Pandit, Premlata; Rakshit, Bipul; Sanyal, Sankar P <br/> <br/>Abstract: From first-principles, the electronic and elastic properties of alkali-metal sulphides (Li₂S, Na₂S), with emphasis on the plane-wave pseudopotential method and the inclusion of the non-linear core correction for exchange and correlation have been investigated. At ambient condition, these compounds are found to crystallize in cubic anti-fluorite structure. This method is found to describe the properties of these materials rather well. In most of the cases, obtained ground state properties are in good agreement with experimental and theoretical results. From the electronic structure calculations, we found that Li₂S is indirect band gap semiconductor whereas Na₂S is direct band gap semiconductor within local density approximation (LDA). <br/> <br/>Page(s): 804-807 Thu, 29 Oct 2009 22:58:59 GMT