http://nopr.niscpr.res.in/handle/123456789/10932 2026-10-12T18:59:52Z 2026-10-12T18:59:52Z Shukla, Manju Brahme, Nameeta Kher, R S Khokhar, M S K http://nopr.niscpr.res.in/handle/123456789/10942 2011-01-27T16:30:40Z 2011-02-01T00:00:00Z

Title: Elementary approach to calculate quantum efficiency of polymer light emitting diodes Authors: Shukla, Manju; Brahme, Nameeta; Kher, R S; Khokhar, M S K Abstract: An elementary approach has been suggested to calculate the external quantum efficiency (<i>EQE</i>) of polymer light emitting diodes (PLEDs). This approach requires only the electroluminescence (EL) spectrum and illumination versus current characteristics of the devices to calculate the <i>EQE</i>. In these calculations the light emission has been considered to be perfectly diffusive from the emission surface. The efficiencies calculated in this way have been compared with the actual values of the <i>EQE</i>s for the different PLED structures available in the literature. The calculated values have shown good agreement with the measured values. Page(s): 142-145

2011-02-01T00:00:00Z Tangsrirat, Worapong Channumsin, Orapin http://nopr.niscpr.res.in/handle/123456789/10941 2011-02-05T16:30:46Z 2011-02-01T00:00:00Z

Title: Minimum-component current-mode universal filter Authors: Tangsrirat, Worapong; Channumsin, Orapin Abstract: This paper describes a current controllable current-mode universal filter with three inputs and one output using multi-output current-controlled current conveyors (MOCCCIIs). The proposed circuit consists of the minimum number of active and passive components, i.e. two MOCCCIIs and two grounded capacitors; simultaneous realization of all the standard filtering functions; independent current-control of the natural angular frequency (w_o) and bandwidth (BW); no requirement of component matching conditions; and low passive and active sensitivities. Page(s): 137-141

2011-02-01T00:00:00Z Pradeep, Dushyant Naithani, U C Kumar, A http://nopr.niscpr.res.in/handle/123456789/10940 2011-01-26T16:30:42Z 2011-02-01T00:00:00Z

Title: Electric field dependent sound velocity change in Ba_1−xCa_xTiO₃ ferroelectric perovskites Authors: Pradeep, Dushyant; Naithani, U C; Kumar, A Abstract: By using double time temperature dependent Green’s function technique, an expression for the sound velocity change in the mixed crystal perovskites (Ba_1−xCa_xTiO₃) has been obtained with the help of the modified Silverman-Joseph Hamiltonian. Third- and fourth-order anharmonic and electric moment terms in the modified Hamiltonian for Ba_1−xCa_xTiO₃ crystal perovskites have been considered. The effect of defect, electric field and anharmonic contributions on velocity change in Ba_1−xCa_xTiO₃ for paraelectric phase has been studied. The presence of higher order anharmonicity and electric moment terms decreases the sound velocity. In the vicinity of the phase transition, it decreases as the consequence of the soft mode. It also varies with electric field and defect concentration in Ba_1−xCa_xTiO₃. Page(s): 132-136

2011-02-01T00:00:00Z Kukreti, Ashish Kumar, Ashok Naithani, U C http://nopr.niscpr.res.in/handle/123456789/10939 2011-01-26T16:30:44Z 2011-02-01T00:00:00Z

Title: Electric field dependence of Curie temperature in Ba_xSr₁_-xTiO₃ ferroelectric perovskites Authors: Kukreti, Ashish; Kumar, Ashok; Naithani, U C Abstract: Electric field dependence of Curie temperature in an anharmonic poly crystalline mixture of Ba_xSr₁_-xTiO₃has been calculated in its paraelectric phase from the Silverman-Joseph-Hamiltonian augmented with fourth-order phonon coordinates using double time Green’s functions technique. The field and impurity dependence of the shift in the Curie temperature has been studied. The Curie temperature increases linearly with increase of the external electric field and impurity concentration(<i style="">x</i>) in the Ba_xSr₁_-xTiO₃ ferroelectric perovskites. It follows the Curie-Weiss law above the transition temperature in the paraelectric region. The results are in good agreement with previous experimental and theoretical result Page(s): 126-131

2011-02-01T00:00:00Z