NISCAIR Online Periodicals Repository Collection: IJPAP Vol.46(09) [September 2008]

Log-domain low pass high pass first-order filter

Fri, 29 Aug 2008 22:58:59 GMT

Title: Log-domain low pass high pass first-order filter

Authors: Shah, N A; Iqbal, S Z; Parveen, Nusrat

Abstract: A new first-order log-domain filter topology implementing simultaneously low-pass (LP) and high-pass (HP) filter functions has been presented. The circuit employs log-domain cells, current sources and grounded capacitor. The circuit has simple architecture, wider dynamic range at low power supply and higher frequency operation as it is based on log-exponential relation of a transistor. The electronic tunability of the proposed filter and grounded capacitor make it suitable for construction in IC technology. The PSPICE simulations results are found to be in close conformity with the theoretical results.

Page(s): 667-670

Dielectric spectroscopy of 100 MeV Ag ion irradiated polyetherimide

Fri, 29 Aug 2008 22:58:59 GMT

Title: Dielectric spectroscopy of 100 MeV Ag ion irradiated polyetherimide

Authors: Goyal, Geetika; Quamara, J K

Abstract: The dielectric constant (′) and loss factor (Ɛ′′) have been measured in pristine and 100 MeV Ag ion irradiated (fluences: 5.610¹⁰, 1.810¹¹ and 1.810¹² ions/cm2) polyetherimide (PEI) in the temperature region 30-250C at different frequencies ranging from 200 Hz to 5 MHz. There is an overall increase in Ɛ′ in irradiated samples. This shows the dominance of interfacial polarization arising from the large number of radiation induced defect sites and free radicals. However, the increase in Ɛ′ is not directly proportional to the fluence of irradiance. There is a sudden decline in ′ at intermediate fluence (1.810¹¹ions/cm²) which is due to the occurrence of new secondary radiation induced crystalline (SRIC) phase. In the low temperature region 30-100C, the Ɛ′ follows the Kirkwood model. Above 100C, the Ɛ′ is almost temperature independent. The radiation induced free radical cross-linking and formation of free radicals have been held responsible for this behaviour. Various relaxation processes revealed their presence in the form of loss peaks in Ɛ′′-T curves appearing around 40-50C, 120-130C and 180-220C associated to the dipolar nature of ether linkages, carbonyl groups and space charge relaxation processes, respectively.

Page(s): 660-666

Thermal properties and electrochromic behaviour of PVA complexed electrolytes using PEG as plasticizer

Fri, 29 Aug 2008 22:58:59 GMT

Title: Thermal properties and electrochromic behaviour of PVA complexed electrolytes using PEG as plasticizer

Authors: Gupta, P N

Abstract: Thin films of PVA complexed with H₃PO₄ in different molar ratios using polyethylene glycol (PEG) as plasticizer are prepared by solution cast technique. Thermal study of the system of PVA- H₃PO₄-PEG indicates that glass temperature decreases as acid concentration increases in the presence of the plasticizer and hence, electrical conductivity of the complexed polymer increases. Thin films of higher conductivity are used in the fabrication of electrochromic devices. Optical absorption has been measured in transmission mode and time response of instantaneous change in optical density during colouring and bleaching sequence has been investigated by applying –5.00 to + 5.00V to the WO₃ side with respect to ITO electrode for fixed duration. The modified device using PVA- H₃PO₄-PEG system shows maximum change in optical density (0.13 for the sample PVA- H₃PO₄) and gives higher value of contrast ratio due to high electrical conductivity. It is found that the plasticizer is effective to get shorter response time for the system of PVA- H₃PO₄ -PEG in comparison to the PVA- H₃PO₄ system for which observed colouration and bleaching times are 105 and 85 s, respectively.

Page(s): 657-659

Effect of adatom-phonon interaction on parameters of single walled carbon nanotube

Fri, 29 Aug 2008 22:58:59 GMT

Title: Effect of adatom-phonon interaction on parameters of single walled carbon nanotube

Authors: Patra, S

Abstract: Double time Green function technique and Zubarev equation of motion approach have been employed. The modified dependence with and chemisorption energy (ΔE) with radius of single walled carbon nanotube (SWCNT) was estimated. We considered HF approximation to decouple higher order Green function and found that the inclusion of adatom-phonon interaction, change the surface parameters. The comparison of theoretical predication and experimentally observed value indicates to study in detail from the first principle.

Page(s): 651-656