http://nopr.niscair.res.in/handle/123456789/7627 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/7650 Title: High input impedance voltage mode universal biquad filter <br/> <br/>Authors: Kumar, K; Pal, K <br/> <br/>Abstract: A high input impedance voltage mode universal biquad filter using two operational transconductance amplifiers (OTAs), one current feedback amplifier (CFA), two capacitors and one grounded resistor has been studied. The new circuit has three inputs and single output and can realize all the standard filter functions, that is low pass (LP), high pass (HP), band pass (BP), notch (NH), and all pass (AP) filters without changing the circuit topology. The proposed circuit offers several advantages such as orthogonal controllability of the resonance frequency w₀and quality factor <i>Q</i>. There is no need of one more active element for the realization of all pass filter, high input impedance and low output impedance which is suitable for cascading for higher order filter transfer functions and low active and passive sensitivity performance. <br/> <br/>Page(s): 292-296 http://nopr.niscair.res.in/handle/123456789/7649 Title: Structural and magnetic behaviour of NiFe₂O₄ thin film grown by pulsed laser deposition <br/> <br/>Authors: Dixit, Gagan; Singh, J P; Srivastava, R C; Agrawal, H M; Choudhary, R J; Gupta, Ajay <br/> <br/>Abstract: NiFe₂O₄ thin film has been grown on Si (100) substrate by pulsed laser deposition (PLD) technique. The microstructure of the film was characterised by X-ray diffractometer (XRD) and atomic force microscopy (AFM). Magnetic characterisation has been done by vibrating sample magnetometer (VSM). In order to have comparative study, the bulk (target used for PLD) has also been characterised by XRD and VSM. Grazing incidence X-ray diffractometer (GIXRD) pattern of the film confirms the single spinel phase. Results of AFM have shown that the average grain size of the prepared film is of the order of 47 nm and surface roughness of the order of 3-4 nm. VSM measurements indicate that for the film, both the saturation magnetisation and the coercivity are greater than that of bulk. <br/> <br/>Page(s): 287-291 http://nopr.niscair.res.in/handle/123456789/7648 Title: Modified Ghiorso equation of state for CaMgSi₂O₆ silicate melt at 1673 K <br/> <br/>Authors: Kumar, M S; Sharma, B S <br/> <br/>Abstract: Ghiorso has recently developed a functional form for an equation of state (EOS) of molten silicate liquids. The EOS is designed for application over a wide range of melt compositions which can be used from reference conditions to very high pressures. It is emphasized here that the Ghiorso EOS does not satisfy the thermodynamic boundary conditions at infinite pressure. Ghiorso EOS has been modified to make it consistent with the Stacey thermodynamics at extreme compression. Various relationships between the compression ratio (<i style="">V/V</i>₀) and pressure <i>P</i> have been studied for the silicate melt CaMgSi₂O₆at 1673 K. The pressure-volume isothermal relationship, isothermal bulk modulus <i style="">K</i> and its pressure derivative have been calculated using five different forms of EOS viz. Birch Murnaghan third order EOS, Vinet-Rydberg EOS, Stacey EOS, Ghiorso EOS and the modified Ghiorso EOS. It is found that the modified Ghiorso EOS developed in the present study gives the satisfactory results which is in good agreement with the Stacey reciprocal-<i>K</i>' EOS. <br/> <br/>Page(s): 282-286 http://nopr.niscair.res.in/handle/123456789/7647 Title: Dependence of specific heat on electric field in Ba₁_-xCa_xTiO₃ ferroelectric perovskites <br/> <br/>Authors: Pradeep, Dushyant; Kumar, Ashok; Naithani, U C <br/> <br/>Abstract: The electric field dependence of the specific heat of an anharmonic Ba₁_-xCa_xTiO₃ ferroelectric crystal has been calculated in its paraelectric phase from Silverman-Joseph Hamiltonian augmented with fourth order phonon coordinates using double times Green’s functions. The electric field dependent soft mode contribution to the specific heat is described by appropriate Einstein terms. The variation of the specific heat with temperature and defect parameters has been discussed for different values of field strengths. The effect of defects on specific heat can be observed in the presence of anharmonicity. The specific heat decreases with increase in external field and increases with increase in temperature which is in agreement with the previous results. As the Curie temperature is approached, the Cochran soft mode is held to be responsible for the anomalous behaviour of specific heat. <br/> <br/>Page(s): 276-281