Removal of Cr(VI) using co-immobilized activated carbon and <Emphasis Type="Italic">Bacillus subtilis</Emphasis>: fixed-bed column study

Fixed-bed column studies were conducted to evaluate the potential of co-immobilized (activated carbon and Bacillus subtilis) (CI) beads for the removal of Cr(VI) from aqueous solution. The impact of various parameters such as initial Cr(VI) concentrations (100, 150, and 200 mg/L), flow rate (3, 9, and 15 mL/min), and bed depth (10, 15, and 20 cm) on Cr(VI) adsorption onto CI beads were investigated. The breakthrough time increased with a decrease in initial Cr(VI) concentration and flow rate, and an increase in bed height. The breakthrough data obtained for Cr(VI) removal was more adequately described by the Thomas model with high correlation coefficients (R ² = 0.982). The eluent, 0.1 M NaOH, provided high elution efficiencies (~90 %) in all the six cycles. Obtained results pointed out that CI beads could potentially be used for the removal of Cr(VI) from aqueous solution.     

Classifying Problems on Linear Congruences and Abelian Permutation Groups Using Logspace Counting Classes

In this paper we classify the complexity of several problems based on Abelian permutation groups and linear congruences using logspace counting classes. The problems we consider were defined by McKenzie & Cook (1987).     

Influence of tool material on dynamics of drilling of GFRP composites

Drilling trials have been carried out on glass Fibre reinforced plastics (GFRP) with plain high speed steel (HSS), TiN coated HSS and tipped tungsten carbide drills. Most of the defects in drilling of composites are due to thrust force experienced by the workpiece. The parametric influence on cutting force was experimentally evaluated. The experimental results show that the defects toleranced drilling can be attained by proper selection of cutting parameters and tool material. This is substantiated by monitoring flank wear, hole shrinkage and acoustic emission during drilling.     

3D and simplified pseudo-2D modeling of single cell of a high temperature solid oxide fuel cell to be used for online control strategies

In the current study, a single cell of a planar SOFC is firstly modeled in 3D using commercial SOFC module of ANSYS Fluent and the results are validated against the experimental investigations in the literature. Many researchers have used ANSYS Fluent for simulating solid oxide fuel cells. However, there is a huge gap in the literature on explaining the detailed procedure that should be followed in order to use this software effectively. A thorough step-by-step approach is presented to provide a deep insight into the software. Thereafter, a simplified quasi-2D method with infinitely shorter computational time is developed and the results are compared with the 3D model. It is found that the reduced model is capable of being utilized as an alternate method for both online diagnosis and designing active control strategies.     

Investigation and optimization of lubrication parameters in high speed turning of superalloy Inconel 718

Dry machining is sometimes less effective when higher machining efficiency, better surface finish quality, and severe cutting conditions are required. For these situations, semi-dry operations utilizing very small amount of cutting fluids called minimum quantity lubrication is expected to become a powerful tool and played a significant role in a number of practical applications. It has been observed from the literature survey that a systematic research work has to be carried out to determine the optimum quantity of lubricant with appropriate cutting conditions for achieving better machinability characteristics of a material. Hence, an attempt has been made in this paper to enhance the machinability characteristics in high speed turning of superalloy Inconel 718 using quantity of lubricant, delivery pressure at the nozzle, frequency of pulses, direction of application of cutting fluid, cutting speed, and feed rate as the process parameters. Results indicated that the use of optimized minimum quantity lubrication parameters under pulsed jet mode leads to lower cutting force, cutting temperature, and flank wear.     

Studies on spinel cobaltites,MCo2O4 (M = Mn,Zn, Fe,Ni and Co) and their functional properties

Optimization of electrodes for charge storage with appropriate processing conditions places significant challenges in the developments for high performance charge storage devices. In this article, metal cobaltite spinels of formula MCo₂O₄ (where M = Mn, Zn, Fe, Ni and Co) are synthesized by oxalate decomposition method followed by calcination at three typical temperatures, viz. 350, 550, and 750 °C and examined their performance variation when used as anodes in lithium ion batteries. Phase and structure of the materials are studied by powder x-ray diffraction (XRD) technique. Single phase MnCo2O4,ZnCo2O4 and Co3O4 are obtained for all different temperatures 350 °C, 550 °C and 750 °C; whereas FeCo₂O₄ and NiCo₂O₄ contained their constituent binary phases even after repeated calcination. Morphologies of the materials are studied via scanning electron microscopy (SEM): needle-shaped particles of MnCo₂O₄ and ZnCo₂O₄, submicron sized particles of FeCo₂O₄ and agglomerated submicron particle of NiCo₂O₄ are observed. Galvanostatic cycling has been conducted in the voltage range 0.005–3.0 V vs. Li at a current density of 60 mA g^?1 up to 50 cycles to study their Li storage capabilities. Highest observed charge capacities are: MnCo₂O₄ – 365 mA h g^?1 (750 °C); ZnCo₂O₄ – 516 mA h g^?1 (550 °C); FeCo₂O₄ – 480 mA h g^?1 (550 °C); NiCo₂O₄ – 384 mA h g^?1 (750 °C); and Co₃O₄ – 675 mA h g^?1 (350 °C). The Co₃O₄ showed the highest reversible capacity of 675 mA h g^?1; the NiO present in NiCo₂O₄ acts as a buffer layer that results in improved cycling stability; the ZnCo₂O₄ with long needle-like shows good cycling stability.     

Time trends in the intrafamily distribution of dietary energy in rural India

The intrafamily distribution of dietary energy in 5,458 households from seven states in India was assessed from 24-hour dietary recall data collected by the National Nutrition Monitoring Bureau during 1996-97. The energy consumption, expressed as percentage of recommended dietary intake (%RDI), of preschool children, schoolchildren, and adolescents was compared with that of adult men and women in the same households. Time trends in the intrafamily distribution of dietary energy were assessed by comparing the data with those collected in 1975-80 using the same procedures in the same villages. About one-third of the preschool children had an inadequate intake of energy, even when their adult counterparts had an adequate intake, whereas only about 7% of the preschoolers and their parents were consuming inadequate amounts of energy. The extent of energy inadequacy was much less in adolescents and school-age children than in preschool children. This was true even when the adults in the same households had an adequate energy intake. In 1996-97, there was a significant increase in the proportion of households with preschool children consuming inadequate energy, although both adult men and women were consuming energy-adequate diets as compared with the dietary data collected in the same villages in 1975-80. The results indicate the need to provide effective nutrition education for parents regarding the nutritional needs of their children.     

Removal of nickel(II) ions from aqueous solution using crab shell particles in a packed bed up-flow column

This paper investigates the ability of crab shell to remove nickel(II) ions from aqueous solution in a packed bed up-flow column with an internal diameter of 2 cm. The experiments were performed with different bed heights (15-25 cm) and using different flow rates (5-20 ml/min) in order to obtain experimental breakthrough curves. The bed depth service time (BDST) model was used to analyze the experimental data and the model parameters were evaluated. The column regeneration studies were carried out for seven sorption-desorption cycles. The elutant used for the regeneration of the sorbent was 0.01 M EDTA (disodium) solution at pH 9.8 adjusted using NH4OH. Due to continuous usage of crab shell, a performance loss was observed as the breakthrough curves become more flattened also indicated by the broadened mass transfer zone. The breakthrough time decreased uniformly from 28.1 to 9.5 h as the cycles progressed from one to seven, whereas nickel uptake remained approximately constant throughout the seven cycles. The life-factors for crab shell in terms of critical bed length and breakthrough time were found to be 1.1 cm/cycle and 0.17 per cycle, respectively. The elution efficiency was greater than 99.1% in all the seven cycles. The pH profiles during both sorption and desorption process were also reported. In sorption cycles, there was a sudden raise in pH in the early part of the process and then the pH decreased as the time progressed. In desorption cycles, pH decreased in initial stages and followed by gradual increase in pH, which eventually reached the pH of the inlet elutant.