Strength of lime-fly ash compacts using different curing techniques and gypsum additive

Lime-fly ash mixtures are exploited for the manufacture of fly ash bricks finding applications in load bearing masonry. Lime-pozzolana reactions take place at a slow pace under ambient temperature conditions and hence very long curing durations are required to achieve meaningful strength values. The present investigation examines the improvements in strength development in lime-fly ash compacts through low temperature steam curing and use of additives like gypsum. Results of density-strength-moulding water content relationships, influence of lime-fly ash ratio, steam curing and role of gypsum on strength development, and characteristics of compacted lime-fly ash-gypsum bricks have been discussed. The test results reveal that (a) strength increases with increase in density irrespective of lime content, type of curing and moulding water content, (b) optimum lime-fly ash ratio yielding maximum strength is about 0.75 in the normal curing conditions, (c) 24 h of steam curing (at 80A degrees C) is sufficient to achieve nearly possible maximum strength, (d) optimum gypsum content yielding maximum compressive strength is at 2%, (e) with gypsum additive it is possible to obtain lime-fly ash bricks or blocks having sufficient strength (> 10 MPa) at 28 days of normal wet burlap curing.

Tracing the source of bottled water using stable isotope techniques

The Indian Summer Monsoon (ISM) precipitation recharges ground water aquifers in a large portion of the Indian subcontinent. Monsoonal precipitation over the Indian region brings moisture from the Arabian Sea and the Bay of Bengal (BoB). A large difference in the salinity of these two reservoirs, owing to the large amount of freshwater discharge from the continental rivers in the case of the BoB and dominating evaporation processes over the Arabian Sea region, allows us to distinguish the isotopic signatures in water originating in these two water bodies. Most bottled water manufacturers exploit the natural resources of groundwater, replenished by the monsoonal precipitation, for bottling purposes. The work presented here relates the isotopic ratios of bottled water to latitude, moisture source and seasonality in precipitation isotope ratios. We investigated the impact of the above factors on the isotopic composition of bottled water. The result shows a strong relationship between isotope ratios in precipitation (obtained from the GNIP data base)/bottled water with latitude. The approach can be used to predict the latitude at which the bottled water was manufactured. The paper provides two alternative approaches to address the site prediction. The limitations of this approach in identifying source locations and the uncertainty in latitude estimations are discussed. Furthermore, the method provided here can also be used as an important forensic tool for exploring the source location of bottled water from other regions. Copyright (C) 2011 John Wiley & Sons, Ltd.

Pickup and delivery problem using metaheuristics techniques

Dial-a-ride problem (DARP) is an optimization problem which deals with the minimization of the cost of the provided service where the customers are provided a door-to-door service based on their requests. This optimization model presented in earlier studies, is considered in this study. Due to the non-linear nature of the objective function the traditional optimization methods are plagued with the problem of converging to a local minima. To overcome this pitfall we use metaheuristics namely Simulated Annealing (SA), Particle Swarm Optimization (PSO), Genetic Algorithm (GA) and Artificial Immune System (AIS). From the results obtained, we conclude that Artificial Immune System method effectively tackles this optimization problem by providing us with optimal solutions. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.

Physical chemistry of mixed conducting zirconia ceramics

Suivant la pression partielle d'oxygène, la zircone peut être conducteur ionique ou électronique. Mise au point de méthodes de mesures de f.é.m. permettant de s'affranchir des sources d'erreur introduites par ces propriétés.

Chronicle of Marine Diatom Culturing Techniques

Diatoms are regarded as useful neutral lipid sources, as liquid fuel precursors, as foods for marine culture of zooplankters, larval and post-larval shrimp, copepods, juvenile oysters and as micromachines in nanotechnology. Combining microscopic observation with in situ culturing has been useful in areas of taxonomy, ecology, biomonitoring, biotechnology, etc. This communication reviews various culturing techniques of marine diatoms with the relative merits.

Improved parametric models and DPCM techniques for EGG data compiression

This paper presents a novel algorithm for compression of single lead Electrocardiogram (ECG) signals. The method is based on Pole-Zero modelling of the Discrete Cosine Transformed (DCT) signal. An extension is proposed to the well known Steiglitz-Hcbride algorithm, to model the higher frequency components of the input signal more accurately. This is achieved by weighting the error function minimized by the algorithm to estimate the model parameters. The data compression achieved by the parametric model is further enhanced by Differential Pulse Code Modulation (DPCM) of the model parameters. The method accomplishes a compression ratio in the range of 1:20 to 1:40, which far exceeds those achieved by most of the current methods.

Relaxor behavior of K0.5La0.5Bi2Nb2O9 ceramics

K0.5La0.5Bi2Nb2O9, a relaxor, was synthesized and the structural studies confirmed it to be an n = 2 member of the Aurivillius oxides. The ½{h00} and ½{hk0} types of superlattice reflections in the electron diffraction patterns reflected the presence of ordered polar regions. A broad dielectric peak with frequency dependent dielectric maximum temperature was observed. The dielectric relaxation obeyed the Vogel-Fulcher relation wherein Ea = 0.04 eV, Tf = 428 K,and ωo = 1010 Hz. The diffuseness parameter γ = 2.003 established the relaxor nature and it was attributed to the A-site cationic disorder. The piezoelectric d31 coefficient was 0.5 pC/N at 300 K and 2 pC/N at 480 K.

Ferro electriclike and pyroelectric behavior of CaCu3Ti4O12 ceramics

A ferroelectriclike hysteresis loop was obtained at room temperature for CaCu3Ti4O12 (CCTO) ceramic. The remnant polarization and coercive field for 1100 °C/5 h sintered CaCu3Ti4O12 ceramics were 0.063 μC/cm2 and 195 V/cm, respectively. Remnant polarization increased while the coercive field decreased with increase in sintering temperature/duration, implying that these were microstructural dependent. The observation of the hysteresis loop for CCTO ceramic was corroborated by its pyroelectric behavior, and the pyroelectric current at room temperature was −0.0028 nA. These findings were attributed to the presence of mixed-valent Ti ions, apart from off center displacement of Ti ions in TiO6 octahedra.

Relaxor characteristics of layered Ba1-(3/2)xLaxBi2Nb2O9 ceramics

Barium lanthanum bismuth niobate Ba1−(3/2)xLaxBi2Nb2O9 (x = 0, 0.05, 0.1, and 0.15) powders have been prepared via solid state reaction route. The monophasic layered perovskite nature of each composition of these was confirmed by x-ray diffraction studies. A continuous decrease in the lattice parameter c of parent BaBi2Nb2O9 with increase in La3+ doping level was noteworthy. A decrease in dielectric constant maximum (εm), a shift in dielectric anomaly to lower temperatures (from 488 to 382 K), and an increase in the diffuseness (γ) (from 1.58 to 1.84) of dielectric anomaly were encountered on increasing x from 0 to 0.15. Vogel-Fulcher analyses showed a decrease in freezing temperature (Tf) (from 157 to 40 K) and an increase in the activation energy (0.53 to 1.12 eV) for frequency dispersion with increase in La3+ content. A downward shift in the peak position of the pyroelectric coefficient with increasing La3+ doping level was observed. The observed changes in the above physical properties were attributed to the increase in A-site chemical heterogeneity as a result of aliovalent La3+ doping on Ba2+ sites and associated A-site vacancy formation.

Improved microwave dielectric properties of (Mg1-(x+y)CaxLay)(Ti1-yAly)O3 ceramics

Phase-singular solids of the composition, (Mg1−(x+y) Cax Lay)(Ti1−yAly)O3 (x = 0 to 0.88; y = 0.05 to 0.35) having the cubic perovskite-type structure were prepared by the substitution of La3+ and Al3+ in equivalent quantities which brought about complete miscibility between MgTiO3 and CaTiO3. These ceramics showed relative permittivities of 16.5 to 50 (at 6 GHz) with increasing Ca content, high Q values of 10 000 to 30 000 and retained near-zero temperature coefficients in permittivity at optimum y values. Their dielectric characteristics are better accountable in terms of the positional disorder rather than the tolerance factor of perovskite structure.

Developments in amplitude-comparator techniques for distance relays

The paper reports the development of new amplitude-comparator techniques which allow the instantaneous comparison of the amplitude of the signals derived from primary line quantities. These techniques are used to derive a variety of impedance characteristics. The merits of the new relaying system are: the simple mode of the relay circuitry, the derivation of closed polar characteristics (i.e. quadrilateral) by a single measuring gate and sharp discontinuities in the polar characteristics. Design principles and circuit models in their schematic form are described and, in addition, a comprehensive theoretical basis for comparison is also presented. Dynamic test results are presented for a quadrilateral characteristic of potentially general application.

Optimum Load Shedding Through Programming Techniques

This paper obtains a new accurate model for sensitivity in power systems and uses it in conjunction with linear programming for the solution of load-shedding problems with a minimum loss of loads. For cases where the error in the sensitivity model increases, other linear programming and quadratic programming models have been developed, assuming currents at load buses as variables and not load powers. A weighted error criterion has been used to take priority schedule into account; it can be either a linear or a quadratic function of the errors, and depending upon the function appropriate programming techniques are to be employed.