CFD modeling of erosion wear in pipe bend for the flow of bottom ash suspension

In the present study, erosion wear behavior of slurry pipeline due to solid–liquid suspension in the pipeline has been investigated using commercial computational fluid dynamics (CFD) code FLUENT. A multiphase Euler–Lagrange model was adopted to predict the solid particle erosion wear in a 90° pipe bend for the flow of bottom ash–water suspension. A standard k–ε turbulence modeling scheme was used to simulate the flow through the pipeline. Water and bottom ash were taken as liquid and as a dispersed phase of solid–liquid mixture, respectively. A simulation study for erosion wear in a pipe bend was carried out to investigate the influence of various parameters including velocity, solid concentration, and particle size. The velocity of the bottom ash–water suspension varied from 0.5 to 2.5?m/s for solid concentrations with a range of 2.5 to 10.0% (by volume). The particle diameters of the bottom ash were 162 and 300?µm. The simulation results agree with the results of previous studies.     

CUD@SAT: SAT solving on GPUs

The parallel computing power offered by graphic processing units (GPUs) has been recently exploited to support general purpose applications – by exploiting the availability of general API and the single-instruction multiple-thread-style parallelism present in several classes of problems (e.g. numerical simulations and matrix manipulations) – where relatively simple computations need to be applied to all items in large sets of data. This paper investigates the use of GPUs in parallelising a class of search problems, where the combinatorial nature leads to large parallel tasks and relatively less natural symmetries. Specifically, the investigation focuses on the well-known satisfiability testing (SAT) problem and on the use of the NVIDIA compute unified device architecture, one of the most popular platforms for GPU computing. The paper explores ways to identify strong sources of GPU-style parallelism from SAT solving. The paper describes experiments with different design choices and evaluates the results. The outcomes demonstrate the potential for this approach, leading to one order of magnitude of speedup using a simple NVIDIA platform.     

Fast reactions in slurry reactors: Catalyst particle size smaller than film thickness: Oxidation of aqueous sodium sulphide solutions with activated carbon particles as catalyst at elevated temperatures

Catalyst particles, smaller than the diffusion film thickness, in slurry reactors, can enhance the specific rate of absorption substantially over that in the presence of coarser particles, even when the reaction is sufficiently fast to occur in the film in the absence of catalyst particles. This is illustrated with a study of the kinetics of absorption of oxygen in aqueous solutions of sodium sulphide. This study was carried out in stirred contactors with plane interface of 14.5 and 7.5 cm i.d. at temperatures of 80° to 150°C and a total pressure of 1.5 to 9.5 atm, with or without fine activated carbon particles (average particle size 1.7 and 4.33 microns; 0.01 to 2.0% w/w loading) as a catalyst. Some experiments were also conducted with coarse carbon particles (average particle size 85 microns and particle size > 20 μm). Under certain conditions, in the absence of activated carbon, the absorption is accompanied by fast pseudo first order reaction in the film. In a number of cases with fine carbon particles, the specific rate of absorption increased by a factor of 2 to 11 and in some cases this factor was as high as 14. A simple theory has been developed which indicates that, under certain conditions, at higher catalyst loading, the specific rate of absorption will be inversely proportional to the particle size.     

The effect of dopants on the activity of MoO3/ZSM-5 catalysts for the dehydroaromatisation of methane

The effect of a number of dopants – Co²⁺, Fe³⁺, Al³⁺, Ga³⁺ and P^(V) – on the catalytic activity of MoO₃/ZSM-5 dehydroaromatisation catalysts has been investigated. Promotional effects were observed with Fe³⁺, Al³⁺ and Ga³⁺, whereas P^(V) added in the form of phosphomolybdic acid decreased the benzene formation rate. Doping with Co²⁺ was not observed to produce any promotional effects, aside from an initial high conversion and burst of hydrogen which was short-lived. In the case of iron, although the benzene formation rate was close to that for the non-doped parent catalyst in the early stages, benzene formation was enhanced at longer times on stream and the addition of iron was observed to enhance methane conversion, principally through enhanced coke formation. The addition of gallium was found to produce an enhancement of benzene production in the early stages of reaction, but its principal effect was the reduction of hydrogen producing side reactions associated with the formation of coke. In comparing the effects of metal ion addition, it is notable that the impregnation solutions of Fe³⁺, Al³⁺ and Ga³⁺ are acidic. Possible effects of these dopants such as zeolite dealumination, modification of catalyst acidity and the formation of mixed molybdenum containing phases or re-dispersion of the MoO₃ phase can be advanced as potential explanations for the observed effects.     

Studies on poly(vinylchloride)-based polymer blends intended for medical applications. Part II: Mechanical properties

Binary polyblends of plasticized poly(vinylchloride) (PPVC1) with acrylonitrile-butadiene rubber (NBR1), compounded graft polymer of vinyl chloride and ethylene-vinyl acetate copolymer (EVAPVC) and ternary blends of PPVC1, NBR1, and EVAPVC were formulated to study mechanical properties. For the “pure” components, elongation at break was found to be in the order PPVC1 < EVAPVC < NBR1. Addition of both EVAPVC and NBR1 resulted in improvement of ultimate elongation and tensile energy to break. PPVC1-NBR1 binary blends exhibited synergistic behavior for both ultimate tensile stress and elongation at break, indicating the presence of appreciable specific interactions between the polymers. About 30% replacement of PPVC1 by NBR1 or EVAPVC resulted in marginal fall in modulus and significant improvement in elongation at break. EVAPVC or blends containing EVAPVC had a tendency to creep. A simple generalized equation suggested for various mechanical properties works satisfactorily. The results obtained have practical implications and indicate that PVC-based polyblends can be investigated further for potential applications in medicine.     

Modulation of Ultrafast Conformational Dynamics in Allosteric Interaction of Gal Repressor Protein with Different Operator DNA Sequences

Although all forms of dynamical behaviour of a protein under allosteric interaction with effectors are predicted, little evidence of ultrafast dynamics in the interaction has been reported. Here, we demonstrate the efficacy of a combined approach involving picosecond‐resolved FRET and polarisation‐gated fluorescence for the exploration of ultrafast dynamics in the allosteric interaction of the Gal repressor (GalR) protein dimer with DNA operator sequences O_E and O_I. FRET from the single tryptophan residue to a covalently attached probe IAEDANS at a cysteine residue in the C‐terminal domain of GalR shows structural perturbation and conformational dynamics during allosteric interaction. Polarisation‐gated fluorescence spectroscopy of IAEDANS and another probe (FITC) covalently attached to the operator directly revealed the essential dynamics for cooperativity in the protein–protein interaction. The ultrafast resonance energy transfer from IAEDANS in the protein to FITC also revealed different dynamic flexibility in the allosteric interaction. An attempt was made to correlate the dynamic changes in the protein dimers with O_E and O_I with the consequent protein–protein interaction (tetramerisation) to form a DNA loop encompassing the promoter segment.     

Effect of conventional and microwave heating on the structural and physicochemical properties of silver-doped hydroxyapatite nanopowders

ABSTRACT

This paper discussed the influence of duration and modes of heating on structural and physicochemical properties of silver-doped hydroxyapatite (Ag-HAP) nanopowders (NPs). Conventional electric furnace and microwave (MW) heating modes were employed during the synthesis. MW mode of synthesis was relatively an efficient method as it prepared monolithic HAP NP in just one minute of heating. With the increase in duration of heating in both modes of heating; lattice parameters, crystal size, lattice strain, Ca/P ratio, and degree of crystallinity of HAP phase increased. The morphology of particles was rod-shaped having aspect ratio between 2 and 3. EDX confirmed the presence of Ag and corroborated the formation of apatite. The hydrodynamic diameter of Ag-HAP NPs was significantly bigger than the particle sizes calculated using XRD, FESEM, and TEM. Thus, an overall examination concluded MW as an efficient mode of synthesis, able to produce Ag-HAP NPs in a possible minimum time.     

Polarization study on doped lanthanum gallate electrolyte using impedance spectroscopy

Alternating current complex impedance spectroscopy studies were conducted on symmetrical cells of the type [gas, electrode/La_1−x Sr _x Ga_1−y Mg _y O₃ (LSGM) electrolyte/electrode, gas]. The electrode materials were slurry-coated on both sides of the LSGM electrolyte support. The electrodes selected for this investigation are candidate materials for solid oxide fuel cell (SOFC) electrodes. Cathode materials include La_1−x Sr _x MnO₃ (LSM), La_1−x Sr _x Co _y Fe_1−y O₃ (LSCF), a two-phase particulate composite consisting of LSM and doped-lanthanum gallate (LSGM), and LSCF + LSGM. Pt metal electrodes were also used for the purpose of comparison. Anode material investigated was the Ni + Ce_0.85Gd_0.15O₂ composite. The study revealed important details pertaining to the charge-transfer reactions that occur in such electrodes. The information obtained can be used to design electrodes for intermediate temperature SOFCs based on LSGM electrolytes. This paper was presented at the Fuel Cells: Materials, Processing, and Manufacturing Technologies Symposium sponsored by the Energy/Utilities Industrial Sector & Ground Transportation Industrial Sector and the Specialty Materials Critical Technologies Sector at the ASM International Materials Solutions Conference, October 13–15, 2003, in Pittsburgh, PA. The symposium was organized by P. Singh, Pacific Northwest National Laboratory, S.C. Deevi, Philip Morris USA, T. Armstrong, Oak Ridge National Laboratory, and T. Dubois, U.S. Army CECOM.     

A computer-aided system for sustainability assessment for the die-casting process planning

The sustainability assessment of a product's manufacturing using a life cycle assessment tool utilizes the average sustainability performance of the manufacturing process. Because of using an average of sustainability performance, the crucial information related to manufacturing is lost. Therefore, such an assessment cannot be used to assess and compare the sustainability of a part made using different process plans. In this paper, we propose a new systematic approach for sustainability assessment of the die-casting process planning. A computer-aided system named Sustainability Assessor for Die-casting is presented. Here, we discuss the details of the architecture and working of the proposed system. We assess sustainability using three sustainability indicators, namely, energy use, solid waste, and carbon emissions. The proposed system is verified by comparing results with the actual data measured from the shop floor. The developed system is beneficial for sustainability assessment comparing different plans alongside material properties, ultimately helping the die-casting industry to reduce the carbon emissions and material waste, besides improving energy efficiency.