NOPR Collection:

Synthesis and characterization of NaX and Cu-exchanged NaX zeolites from silica obtained from rice husk ash

2010-04-27T16:30:53Z

Title: Synthesis and characterization of NaX and Cu-exchanged NaX zeolites from silica obtained from rice husk ash Authors: Dalai, Ajay K; Pradhan, Narayan C; Rao, Musti S; Gokhale, K V G K Abstract: Sodium X zeolite and a number of other zeolites such as P_C, HS and analcime were synthesized using rice-husk ash as a source of silica. Also, a number of NaCuX zeolites were prepared by ion-exchange method with copper contents from 2.8 to 10.5 wt%. The products were characterized using X-ray diffraction analysis. The morphological characteristics of the prepared zeolites were also studied. The NaX zeolite exhibits typical octahedral form whereas analcime and zeolite P_C have trapezohedral and spheroid forms, respectively. Differential thermal patterns of NaCuX zeolites revealed the presence of an initial sharp and intense endotherm for dehydration around 190-220^oC followed by an exotherm around 830-860^oC representing structural change and dissociation, which were confirmed by X-ray diffraction analysis. Page(s): 227-234

A study on cement mortars incorporating plain Portland cement (PPC), ground granulated blast-furnace slag (GGBFS) and basaltic pumice

2010-04-28T16:30:41Z

Title: A study on cement mortars incorporating plain Portland cement (PPC), ground granulated blast-furnace slag (GGBFS) and basaltic pumice Authors: Binici, Hanifi; Aksogan, Orhan; Kaplan, Hasan Abstract: In this paper, an experimental investigation on the effect of ternary blending on the various properties of cement paste and mortar has been reported. The ternary blended cements have been prepared by using one type of clinker and two types of pozzolans. Two types of grinding techniques, two different fineness values and varying amounts of additives have been employed. Besides these, control pastes and mortars are prepared. The influence of fineness, different grinding techniques and other parameters on the strength of the ternary blended cements has been evaluated. The chemical compositions of the pozzolans are consistent with the requirements given in both the TS 25 (a Turkish standard) and ASTM C 168 standards. The results indicate that the basaltic pumice used in this study, taken from the Osmaniye-Adana province (Southern Turkey), can be used as an admixture in cement production. SEM, XRD and thin section analyses showed that a large quantity of sheet-like CSH was formed when a combination of basaltic pumice and slag were incorporated in the mortar. Page(s): 214-220

Effect of anisotropy on laminated composite plates containing circular holes

2010-04-30T16:30:39Z

Title: Effect of anisotropy on laminated composite plates containing circular holes Authors: Arslan, H Murat Abstract: In this study, an analysis of fibre reinforced, multi-layered composite plates, containing circular holes, has been carried out. First, stress concentrations around a circular hole are studied. A number of diagrams are drawn to show stress concentrations around a hole, for each layer, using different material pairs with different E₁/E₂ ratios (ratio of elasticity modulus of fibre direction to that of transverse direction). The graphs are given, for various E₁/E₂ values, for the circumferential stress values around the hole versus angular location of points, for two different fibre orientation angles. Second, the failure of the laminated composite plate is studied. For this purpose Tsai-Hill failure criterion and Hoffman failure criterion are introduced. To determine the “first-ply failure” of a laminated plate, these two failure criteria are employed. Finally, to show the effect of E₁/E₂ ratio on the failure of plates a number of tables are given for different fibre orientation angles. Page(s): 207-213

On the jitter performance of a quantizer based modified DPLL

2010-05-01T16:30:27Z

Title: On the jitter performance of a quantizer based modified DPLL Authors: Banerjee, T; Sarkar, B C Abstract: The paper examines the effect of an additional derivative control signal (ADCS) on the steady state phase jitter characteristics of first and second order digital phase locked loops (DPLLs) having a finite level quantizer. It has been shown that the ADCS reduces the steady state phase jitter variance particularly when the DPLL gain parameters are high and the input signal has large frequency detuning. Further, a prefixed amount of SSPJ variance can be achieved in presence of the ADCS for a loop with a quantizer having lesser number of levels. The simulation results obtained have been qualitatively interpreted. Page(s): 182-188