Electrocoagulative treatment of mercury containing aqueous solutions

In recent years, electrocoagulation has been successfully used for wastewater treatment and is efficient in heavy metal ions removal. In the present work, electrocoagulation has been used for the removal of Hg(II) from synthetic wastewaters containing up to 20 mg/L of mercury. The electrode materials used are stainless steel (SS) and aluminum (Al). The effects of operating parameters, viz., current density, time of electrocoagulation, distance between electrodes, initial pH of the solution, presence of electrolyte in the solution and temperature have been studied. It was observed that more than 99% Hg(II) removal can be achieved by keeping the distance between SS and Al electrodes from 2 to 6 cm and initial pH range from 3 to 7. The results show that the pseudo second-order kinetics fits the data well. Also, preliminary cost estimation was reported.     

An uncalibrated lightfield acquisition system

Acquisition of image data for lightfield usually requires an expensive, complex and bulky setup. In this paper, we describe a simple method of acquiring the image data set. The method requires a normal handheld video camera, which is taken around the object to be rendered. We employ homography from the viewing/camera plane to the lightfield plane for obtaining the ray intersections with the lightfield planes. The computations involved are simple and make the method suitable for online lightfield acquisition.     

Tailoring structural and electrical properties of A-site non-stoichiometric Na0.5Bi0.5TiO3 ceramic at different sintering temperature

Na/Bi stoichiometry plays crucial role in determining various properties of sodium bismuth titanate-based system. In this work, we have synthesised lead free (Na_0.5Bi_0.5)_1+x TiO₃ (x?=?0, 0.02 and 0.05) ceramics by sol-gel method and systematically presented structural, dielectric and ferroelectric properties at different sintering temperature. Single phase perovskite structure with rhombohedral symmetry (R3c) is obtained for all compositions from low (850°C) to maximum (1150°C) sintering temperature. The shifting of x-ray diffraction peaks and characteristic perovskite metal-oxide vibrational band (～627?cm^?1) in Fourier Transform Infra-red spectra suggests compression or expansion of crystal lattice with Na/Bi non-stoichiometry. Excess of Na/Bi comprises dense crystal growth as compared to pure Na_0.5Bi_0.5TiO₃ composition suggesting compensation of volatile elements loss during heat treatment whose impact has also been observed in dielectric as well as ferroelectric properties. It is observed that Na_0.51Bi_0.51TiO₃ sample with x?=?0.02 exhibits better structural, dielectric and ferroelectric properties in whole range of sintering temperature.     

Quantitative Risk Assessment for Process Design Modification and Maintenance Optimization in Refineries and Petrochemical Plants

Quantitative risk assessment is methodology based on calculating probabilities and frequencies of sequential events using Boolean algebra, and it is normally used to perform safety assessments for complex interacting systems. Although quantitative risk assessment has been commonly used in aerospace and nuclear industries, it can also be used for quantifying economic risk and for estimating possibilities of potential production losses in a petrochemical or a manufacturing plant. In developing quantitative risk assessment models for petrochemical plants, component failures as well as human (operator) errors are taken into consideration in developing the plant's fault‐tree logic, in which is used to predict probabilities of future plant upsets. This paper shows how the quantitative risk assessment can be used to rank the economic importance of the production units in a refinery for prioritizing maintenance activities. In addition, two case studies are compared to demonstrate how a quantitative risk assessment model can be used as an invaluable tool in process design optimization. The quantitative risk assessment methodology developed in this work relates production losses to the performance of the major components and the process design. This application of the quantitative risk assessment provides a basis for the risk‐informed decision‐making and optimizing allocation of plant resources in support of plant operation and maintenance activities.     

Pore-network modeling of liquid water transport in gas diffusion layer of a polymer electrolyte fuel cell

A pore-network model is developed to study the liquid water movement and flooding in a gas diffusion layer (GDL), with the GDL morphology taken into account. The dynamics of liquid water transport at the pore-scale and evolution of saturation profile in a GDL under realistic fuel cell operating conditions is examined for the first time. It is found that capillary forces control liquid water transport in the GDL and that liquid water moves in connected clusters with finger-like liquid waterfronts, rendering concave-shaped saturation profiles characteristic of fractal capillary fingering. The effect of liquid coverage at the GDL–channel interface on the liquid water transport inside GDL is also studied, and it is found that liquid coverage at the GDL–channel interface results in pressure buildup inside the GDL causing the liquid water to break out from preferential locations.     

First-line chemotherapy for advanced ovarian cancer: paclitaxel, cisplatin and the evidence

As of June 1998, four randomized trials have been completed comparing the combination of paclitaxel and cisplatin with a cisplatin-based control arm. The results of three of these trials are available; one has been published as a full paper, the other two in abstract form only. Two of the reported trials (GOG-111 and the Intergroup trial) provide clear evidence that cisplatin combined with paclitaxel is a more effective regimen than one using the same dose of cisplatin combined with cyclophosphamide. The results of the third reported trial (GOG-132) are rather different, suggesting that a higher dose of single-agent cisplatin may be as effective as the paclitaxel/cisplatin combination tested in the other two trials. A number of explanations for these unexpected results have been proposed: false-positive results in GOG-111 and the Intergroup trial; false-negative results in GOG-132; high crossover in GOG-132 (including crossover before progression); the cyclophosphamide in the control arm of GOG-111 and the Intergroup trial had a negative impact on outcome in the control group in these trials; the higher dose of cisplatin when used as a single agent in GOG-132 had a positive impact on outcome for the control group in this trial. These explanations are discussed in detail, and their implications explored.     

Plastic expansion of a circular hole in sheet metal subjected to biaxial tensile stress

A new yield function proposed by Hill is used to predict the plastic stress and strain distributions in an annulus of sheet metal subjected to a radial tension at its outer periphery. The new yield function has greater generality than the original anisotropic yield function. The theoretical predictions show good correlation with experimental strain distributions measured for sheets of aluminium killed steel, soft aluminium of commercial purity and soft 70/30 brass. There is seen to be a need for the experimental determination of more complete yield loci for sheet metal.     

A new model for the prediction of instability and limit strains in thin sheet metal

It is proposed that the increase in surface roughness which occurs with increasing strain reduces the effective thickness of a plastically stretched sheet metal so that a tensile instability condition occurs at surface strains smaller than those predicted by the classical analysis. It is thought that the empirical relationship for growth of surface roughness is introduced in a realistic manner although it is recognized that there is a need for more precise information of the effect of the surface grains on the load carrying capacity of the sheet metal.Limit strains are predicted on the assumption that an incipient neck at the instability condition develops into a groove. The growth of surface roughness is taken into account throughout the deformation and note is taken of the fact that the surface roughness effect is superimposed on the developing groove.     

Growth of voids in biaxial stress fields

The relative density changes occurring in some commercial sheet metals as a result of plastic deformation have been determined using a differential method based on Archimedes' principle. Two batches of aluminium killed steel, soft brass and soft commercial purity aluminium were stretched in balanced biaxial tension using Marciniak's technique and the density changes measured at increasing plastic strains. One of the steels was also tested in plane strain tension and at a ratio . The largest relative density change, 0·005, occurred in one of the steels at a natural surface strain of approximately 0·4. It was found that the density changes are dependent on the amount of plastic work but independent of the applied strain ratio.Three stages are identified for relative density changes in steel. During the first stage existing voids expand and new voids are initiated. The second stage is the expansion of a constant number of voids while the third stage, leading to fracture, is characterised by local rather than uniform bulk deformation. Experimental results for the expansion of model voids are consistent with the observations of the second stage.     

Two-phase modeling of gas purge in a polymer electrolyte fuel cell

Gas purge intended to minimize residual water in a polymer electrolyte fuel cell (PEFC) is critical for successful shutdown and sub-zero startup. In the present work, we present a two-phase transient model describing water removal from PEFC under gas purge conditions. The role of back diffusion from the cathode to anode along with liquid water transport in the gas diffusion layers behind the drying front and vapor diffusion ahead of the drying front is highlighted. The underlying ineffectiveness of cathode-only purge is outlined. The model predictions are compared with experimental results under various purge conditions. A good match with experiments is obtained at higher purge temperatures whereas some differences in the HFR profile is observed at lower temperatures. The role of drying front morphology in addressing the observed differences between numerical and experimental results is hypothesized.