http://nopr.niscair.res.in/handle/123456789/8611 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/8621 Title: Synthesis and characterization of cation-doped BiFeO₃ materials for photocatalytic applications <br/> <br/>Authors: Madhu, C; Bellakki, Manjunath B; Manivannan, V <br/> <br/>Abstract: A sol-gel method was applied to synthesize Bi_1-xM_xFeO₃ (M = Mg, Al, Y) ceramic materials. Subsequently, these materials were structurally characterized by applying Rietveld refinement techniques. The magnetic properties of the synthesized materials were determined by SQUID measurements and their optical properties (band-gap) were determined by applying diffused reflectance (DR) techniques. The low band-gap nature of these materials enabled to them exhibit photocatalytic activity and accordingly 2% Y doped BiFeO₃ samples exhibited higher photocatalytic effect (18% compared to 14% for undoped). Under identical conditions, TiO₂standard exhibited only 7% degradation indicating superior properties of cation-doped bismuth ferrites. <br/> <br/>Page(s): 131-139 Mon, 29 Mar 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8620 Title: Mitigation of voltage sags in a distribution system due to three phase to ground fault using DVR <br/> <br/>Authors: Chowdary, D Deepak; Kumar, G V Nagesh <br/> <br/>Abstract: Voltage sags defined as short-duration reductions in the rms voltage on one or more electrical phases are becoming the most important power quality concern to electric utility customers with sensitive loads. They are characterized by their magnitude and duration (which is typically 0.5 to 30 cycles). Sags are predominantly caused by faults that are unavoidable on the distribution systems due to the interconnectivity of the utility systems. The distribution-class dynamic voltage restorer (DVR) is a series connected power electronics device which can compensate for distribution system sags and swells. By enhancing the voltage, the DVR can increase the availability of sensitive loads. For a successful compensation, the DVR must be able to detect the voltage sag and control the inverter to restore the voltage. The sliding mode control is used for the DVR. Using sliding mode control to the DVR, additional sag detection method is eliminated. This improves the dynamic response of the DVR and also DVR is able to compensate for any variation in source voltage. In this paper, a DVR with sliding mode control strategy is used to alleviate the voltage sags caused due to faults occurring on the parallel feeders in a single-phase distribution system. The DVR along with the other parts of the distribution system are simulated using MATLAB/SIMULINK. <br/> <br/>Page(s): 113-122 Mon, 29 Mar 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8619 Title: Novel current-mode and voltage-mode universal biquad filters using single CFTA <br/> <br/>Authors: Tangsrirat, Worapong <br/> <br/>Abstract: This paper presents two novel electronically tunable universal filter configurations employing a single new active device, namely the current follower transconductance amplifier (CFTA). The first proposed current-mode universal filter with single input and three outputs consists of one CFTA, one virtually grounded resistor and two grounded capacitors. It can simultaneously realize low-pass, band-pass and high-pass responses with no need to impose component choice. A new three-input single-output universal voltage-mode biquad using one CFTA, two resistors and two capacitors is also proposed as a second proposed circuit. The latter circuit can be configured to realize all the five standard biquadratic filter functions; low-pass, band-pass, high-pass, band-stop and all-pass, without changing the circuit configuration. Both two universal biquad filters also offer the advantage features of the use of minimum number of passive components, and independent electronic tuning of the important filter parameters (<i>ω_o</i> and BW), as well as low active and passive sensitivities. To demonstrate the performances of the proposed filters and verify the theory, PSPICE simulations are accomplished. <br/> <br/>Page(s): 99-104 Mon, 29 Mar 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/8618 Title: Strength and capillary water absorption of lightweight concrete under different curing conditions <br/> <br/>Authors: Bozkurt, Nusret; Yazicioglu, Salih <br/> <br/>Abstract: This paper reports an experimental study carried out to investigate the influence of addition of pozzolanic materials and curing regimes on the mechanical properties and the capillary water absorption (sorptivity) characteristics of lightweight concrete. A control lightweight concrete mixture made with lightweight volcanic pumice containing only Portland cement (PC) and fly ash lightweight concrete mixture containing 20% of fly ash (FA) and 10% of silica fume (SF) as a replacement of the cement by weight is prepared. The specimens are prepared and cured in three different curing conditions (standard 20°C water, sealed and air cured) for the periods of 3, 7 and 28 days. At the end of each curing period, compressive and tensile strengths and ultrasonic pulse velocity (UPV) values are determined; sorptivity coefficients are recorded at 28 days. The results indicate that SF specimens give higher compressive and tensile strength and lower sorptivity coefficient values than corresponding PC and FA concrete specimens, regardless of curing regime and age of concrete. The results also show a good correlation between the strength development of concrete and its sorptivity, i.e., as the compressive and tensile strengths increased due to the hydration, the sorptivity coefficients decreased significantly. <br/> <br/>Page(s): 145-151 Mon, 29 Mar 2010 22:58:59 GMT