NISCAIR Online Periodicals Repository Collection: IJPAP Vol.50(08) [August 2012]

Current-mode high-Q bandpass filter and mixed-mode quadrature oscillator using ZC-CFTAs and grounded capacitors

Sun, 29 Jul 2012 22:58:59 GMT

Title: Current-mode high-Q bandpass filter and mixed-mode quadrature oscillator using ZC-CFTAs and grounded capacitors

Authors: Tangsrirat, Worapong; Mongkolwai, Pratya; Pukkalanun, Tattaya

Abstract: This paper presents the realization of the current-mode bandpass filter and mixed-mode quadrature oscillator both from the same circuit configuration. The proposed circuit is in the resistor-less structure, which contains only four z-copy current follower transconductance amplifiers (ZC-CFTAs) as active components together with two grounded capacitors as passive components. As the first configuration, the current-mode BP filter with high quality factor (Q) is proposed. The center frequency (w_o) and the Q of the circuit are orthogonal adjustable via the g_m-value of the ZC-CFTA. From the same topology, the mixed-mode quadrature oscillator can easily be realized that is capable of generating two explicit quadrature current outputs and two quadrature voltage outputs, simultaneously. Moreover, the realized oscillator also provides the advantage of orthogonal electronic control of the oscillation condition and oscillation frequency, which makes it suitable as variable frequency oscillator. PSPICE simulation results using bipolar ZC-CFTA have been given to verify the workability of the two proposed circuits.

Page(s): 600-607

Design and development of atomic flux controller for cesium Fountain clock at NPL, India

Sun, 29 Jul 2012 22:58:59 GMT

Title: Design and development of atomic flux controller for cesium Fountain clock at NPL, India

Authors: Pant, Kavindra; Arora, Poonam; Yadav, Suchi; Gupta, Amitava Sen

Abstract: In the present paper, the development of an electronic module for controlling the atomic flux from Cesium (Cs) Source (Cs ampoule) to the cooling chamber of Physics package of Cs fountain clock being developed at National Physical Laboratory (NPL) India, is described. Cs source is integrated with octagonal cooling chamber and the amount of Cs diffusing into the chamber is controlled by controlling the temperature of Cs ampoule. The atomic flux controller is basically a temperature controller which is designed for maintaining the temperature from 10°C to 80°C. It is based on lock-in amplifier and proportional-integral-differential (PID) controller techniques for precise control of temperature. We have used Thermoelectric Coolers (TECs) for cooling and heating the Cs ampoule.

Page(s): 593-599

Vapour-liquid equilibria in binary systems formed by methylocyclopentane with alcohols

Sun, 29 Jul 2012 22:58:59 GMT

Title: Vapour-liquid equilibria in binary systems formed by methylocyclopentane with alcohols

Authors: Kosowski, Andrzej; Gierycz, Paweł

Abstract: The modified Świętosławski ebulliometer was used for the accurate (uncertainty of measurements: 0.01 K, in the case of the temperature and 30 Pa, in the case of the pressure) determination of vapour-liquid equilibria in binary isothermal systems formed by methylcyclopentane with the following: 2-butanol, 2-pentanol K and 2-methyl-2-butanol from 313.25 K to 343 K. The vapour pressures of the pure substances are also given. The experimental data have been correlated by means of the Redlich-Kister, NRTL and Wilson equations.

Page(s): 583-592

Solvothermal synthesis and crystal structure of aluminogermanate halide sodalites using organic solvent

Sun, 29 Jul 2012 22:58:59 GMT

Title: Solvothermal synthesis and crystal structure of aluminogermanate halide sodalites using organic solvent

Authors: Borhade, Ashok V; Dholi, Arun G; Tope, Dipak R; Wakchaure, S G

Abstract: Solvothermal synthesis has been investigated for the crystallization of aluminogermanate sodalite containing halide (Cl, Br and I) in 50% ethyl alcohol at low temperature. It was found that 50% ethanol+ 50% water is good solvent system for sodalite. X-ray powder diffraction, IR, ²⁷Al and ²³Na MAS NMR, SEM and thermogravimetry are used to characterize these sodalites. The crystal structures show cubic symmetry in a space group P 3n and were refined by Rietveld refinement method. The unit cell parameter, a = 9.0641, 9.1049 and 9.1874Å and the corresponding Al-O-Ge angles are found to be 133.702, 135.346 and 137.628° for chloro, bromo and iodo sodalite,respectively. The MAS NMR study confirms alternating Al and Ge ordering of sodalite framework. The thermal stability of guest anions in the sodalite framework was studied by thermogravimetric analysis.

Page(s): 576-582