Gas-liquid two phase flow through a vertical 90deg elbow bend

Pressure drop data are reported for two phase air-water flow through a vertical to horizontal 90° elbow bend set in 0.026 m i.d. pipe. The pressure drop in the vertical inlet tangent showed some significant differences to that found for straight vertical pipe. This was caused by the elbow bend partially choking the inflow resulting in a build-up of pressure and liquid in the vertical inlet riser and differences in the structure of the flow regimes when compared to the straight vertical pipe. The horizontal outlet tangent by contrast gave data in general agreement with literature even to exhibiting a drag reduction region at low liquid rates and gas velocities between 1 and 2 m s -1. The elbow bend pressure drop was best correlated in terms of le/d determined using the actual pressure loss in the inlet vertical riser. The data showed a general increase with fluid rates that tapered off at high fluid rates and exhibited a negative pressure region at low rates. The latter was attributed to the flow being smoothly accommodated by the bend when it passed from slug flow in the riser to smooth stratified flow in the outlet tangent. A general correlation was presented for the elbow bend pressure drop in terms of total Reynolds numbers. A modified Lockhart-Martinelli model gave prediction of the data.

Simple models of complex aggregation: Vesicle formation by soft repulsive spheres with dipolelike interactions

Structural and thermodynamic properties of spherical particles carrying classical spins are investigated by Monte Carlo simulations. The potential energy is the sum of short range, purely repulsive pair contributions, and spin-spin interactions. These last are of the dipole-dipole form, with however, a crucial change of sign. At low density and high temperature the system is a homogeneous fluid of weakly interacting particles and short range spin correlations. With decreasing temperature particles condense into an equilibrium population of free floating vesicles. The comparison with the electrostatic case, giving rise to predominantly one-dimensional aggregates under similar conditions, is discussed. In both cases condensation is a continuous transformation, provided the isotropic part of the interatomic potential is purely repulsive. At low temperature the model allows us to investigate thermal and mechanical properties of membranes. At intermediate temperatures it provides a simple model to investigate equilibrium polymerization in a system giving rise to predominantly two-dimensional aggregates.

Stabilization of zinc electrodes with a conducting polymer

The reversibility of zinc anode in alkaline medium was enhanced by electrostatic deposition of a conducting polymer (polypyrrole). Electropolymerization of pyrrole onto zinc in aqueous medium using an organic acid as dopant is feasible and preferred as zinc is less corrosive in this medium. The structure of the polymer film was analyzed by FT-IR spectroscopy and scanning electron microscopy. The effect of the polypyrrole deposit on the zinc electrode was studied by cyclic voltammetry and charge–discharge cycling.

Studies on polypyrrole film in room temperature melt

A bluish-black shining free standing polypyrrole film (PPy) of electronic conductivity 130 S cm-1 has been prepared by electrochemical oxidative polymerization of pyrrole on Pt/transparent glass conducting electrode resistance 15 O cm-1, using a room temperature melt as an electrolyte, composed of 1:3 stoichiometric ratio of cetyl pyridinium chloride and anhydrous aluminum chloride at 0.58 V versus Al wire as a reference electrode. The film possessed a charge transfer resistance of 132 O, and showed two absorption peaks at 457 and 1264 nm in the UV-vis–NIR diffused reflectance spectra. The morphology of the film was hexagonal. The potential step technique suggested a layered structure. This thin film can easily be peeled off from the electrode surface after three cycles and can be used for various applications like dissipation of electrostatic charge, battery electrode materials, solid electrolytic capacitor, electrochromic windows and displays, microactuators etc. It was also characterized by IR, thermal and SEM studies.

Dissipative scheme to approach the boundary of two-qubit entangled mixed states

We discuss the generation of states close to the boundary family of maximally entangled mixed states as defined by the use of concurrence and linear entropy. The coupling of two qubits to a dissipation-affected bosonic mode is able to produce a bipartite state having, for all practical purposes, the entanglement and mixedness properties of one of such boundary states. We thoroughly study the effects that thermal and squeezed characters of the bosonic mode have in such a process and we discuss tolerance to qubit phase-damping mechanisms. The nondemanding nature of the scheme makes it realizable in a matter-light-based physical setup, which we address in some details.

Chemical Processes in Protoplanetary Disks

We have developed a high-resolution combined physical and chemical model of a protoplanetary disk surrounding a typical T Tauri star. Our aims were to use our model to calculate the chemical structure of disks on small scales (submilliarcsecond in the inner disk for objects at the distance of Taurus, ~140 pc) to investigate the various chemical processes thought to be important in disks and to determine potential molecular tracers of each process. Our gas-phase network was extracted from the UMIST Database for Astrochemistry to which we added gas–grain interactions including freezeout and thermal and non-thermal desorption (cosmic-ray-induced desorption, photodesorption, and X-ray desorption), and a grain-surface network. We find that cosmic-ray-induced desorption has the least effect on our disk chemical structure while photodesorption has a significant effect, enhancing the abundances of most gas-phase molecules throughout the disk and affecting the abundances and distribution of HCN, CN, and CS, in particular. In the outer disk, we also see enhancements in the abundances of H2O and CO2. X-ray desorption is a potentially powerful mechanism in disks, acting to homogenize the fractional abundances of gas-phase species across the depth and increasing the column densities of most molecules, although there remain significant uncertainties in the rates adopted for this process. The addition of grain-surface chemistry enhances the fractional abundances of several small complex organic molecules including CH3OH, HCOOCH3, and CH3OCH3 to potentially observable values (i.e., a fractional abundance of greater than 10-11).

Hydrophobic substances induce water stress in microbial cells

Ubiquitous noxious hydrophobic substances, such as hydrocarbons, pesticides and diverse industrial chemicals, stress biological systems and thereby affect their ability to mediate biosphere functions like element and energy cycling vital to biosphere health. Such chemically diverse compounds may have distinct toxic activities for cellular systems; they may also share a common mechanism of stress induction mediated by their hydrophobicity. We hypothesized that the stressful effects of, and cellular adaptations to, hydrophobic stressors operate at the level of water : macromolecule interactions. Here, we present evidence that: (i) hydrocarbons reduce structural interactions within and between cellular macromolecules, (ii) organic compatible solutes-metabolites that protect against osmotic and chaotrope-induced stresses-ameliorate this effect, (iii) toxic hydrophobic substances induce a potent form of water stress in macromolecular and cellular systems, and (iv) the stress mechanism of, and cellular responses to, hydrophobic substances are remarkably similar to those associated with chaotrope-induced water stress. These findings suggest that it may be possible to devise new interventions for microbial processes in both natural environments and industrial reactors to expand microbial tolerance of hydrophobic substances, and hence the biotic windows for such processes.

Enhancement of the stability of microporous silica films in non-aqueous solvents at elevated temperature

The effect of Al incorporation and pH adjustment during hydrolysis of the silica precursor on the thermal and structural stability of ordered microporous silica films with a 2D structure is presented. The structural stability of the films was determined from a combination of LA XRD/TEM data with porosity data obtained from ethanol adsorption isotherms. Thermogravimetric analysis and MR data were used to determine the template removal and the thermal stability. Stability of aluminium incorporated silica films has further been examined in several organic solvents with different polarity. A solvent with a higher polarity interacts more strongly with the films; the long-order structure disappeared after exposure to polar solvents. After exposure to non-polar solvents, the pore size uniformity was retained after 48 h. The samples with an Al/Si ratio of 0.007 showed the smallest d-spacing shift after exposure to hexane. The stability was further tested in the hydrogenation of phenylacetylene performed in a batch reactor over 1 wt.% Pd/Si(Al)O-2/Si (Al/Si = 0.007) films at 30 degrees C and 10 bar H-2 with hexane as solvent. No deactivation was observed in two subsequent hydrogenation runs. (C) 2009 Elsevier Inc. All rights reserved.

Numerical simulation of a patent technology for sealing of deep-sea oil wells using nonlinear finite element method

For over 50 years bridge plugs and cement have been used for well abandonment and work over and are still the material of choice. However the failures of cement abandonments using bridge plugs has been reported on many occasions, some of which have resulted in fatal consequences. A new patented product is designed to address the shortcomings associated with using bridge plugs and cement. The new developed tools use an alloy based on bismuth that is melted in situ using Thermite reaction. The tool uses the expansion properties of bismuth to seal the well. Testing the new technology in real field under more than 2 km deep sea water can be expensive. Virtual simulation of the new device under simulated thermal and mechanical environment can be achieved using nonlinear finite element method to validate the product and reduce cost. Experimental testing in the lab is performed to measure heat generated due to thermite reaction. Then, a sequential thermal mechanical explicit/implicit finite element solver is used to simulate the device under both testing lab and deep water conditions.

Structure-reactivity Correlations in the catalytic coupling of ethyne over novel bimetallic Pd/Sn catalysts

The structure, thermal stability, and catalytic behavior of a novel highly dispersed silica-supported Pd/Sn catalyst prepared by an organometallic route have been examined by X-ray photoelectron, X-ray diffraction, and X-ray absorption, fine structure spectroscopies, the latter two measurements being carried outwith an in situ reaction cell. Additional reactor measurements were performed on a more Sn-rich catalyst and on a pure Pd catalyst. Varying the temperature of reduction induced large variations in catalytic performance toward ethyne-coupling reactions. These changes are understandable in terms of the destruction of SnO2-like structures surrounding the Pd core, yielding a skin of metallic Sn which subsequently undergoes intermixing with Pd. The overall thermal and catalytic behavior of these highly dispersed materials accords well with the analogous single-crystal model system.

Natural convection experiments on a heated horizontal cylinder in a differentially heated square cavity

Natural convection heat transfer from a heat generating horizontal cylinder enclosed in a square cavity, where a temperature difference exists across its vertical walls has been experimentally investigated for the range 2×104

Fibre embedding in aluminium alloy 3003 using ultrasonic consolidation process-thermo-mechanical analyses

This work presents a computational framework based on finite element methods to simulate the fibre-embedding process using ultrasonic consolidation process. The computational approach comprises of a material model which takes into account thermal and acoustic softening effects and a friction model which indicates the realistic friction behaviour at the interfaces. The derived material model and developed friction model have been incorporated in finite element model. Using the implemented material and friction model, thermo-mechanical analyses of embedding of fibre in aluminium alloy 3003 has been performed. Effect of different process parameters, such as velocity of sonotrode, displacement amplitude of ultrasonic vibration and applied loads, is studied and compared with the experimental results. The presented work has specially focused on the quality of the developed weld which could be evaluated by the friction work and the coverage of the fibre which is estimated by the plastic flow around the fibre. The computed friction work obtained from the thermomechanial analyses performed in this study show a similar trend as that of the experimentally found fracture energies. © Springer-Verlag London Limited 2010.

Local materials for building houses: laterite valorization in Africa

This paper presents the preliminary results of geological and geomechanical studies on the laterite stone exploited at Dano quarry in Burkina Faso. The field work described the geological structure of quarry sites and their environment to determine the rocks alteration and the links between the bedrock and lateritic material. Physic-mechanical properties have been studied for assessing the potentiality of this material for lightweight housing, to be completed with thermal and environmental considerations. Some social and economic evaluations are in progress in order to foster its utilization under local conditions.

Local materials for building houses: Laterite valorization in Africa

This paper presents the preliminary results of geological and geomechanical studies on the laterite stone exploited at Dano quarry in Burkina Faso. The field work described the geological structure of quarry sites and their environment to determine the rocks alteration and the links between the bedrock and lateritic material. Physic-mechanical properties have been studied for assessing the potentiality of this material for lightweight housing, to be completed with thermal and environmental considerations. Some social and economic evaluations are in progress in order to foster its utilization under local conditions. © (2014) Trans Tech Publications, Switzerland.

Carboxyl functionalised MWCNT/Polymethyl methacrylate bone cement for orthopaedic applications

The incorporation of carboxyl functionalised multi-walled carbon nanotube (MWCNT-COOH) into a leading proprietary grade orthopaedic bone cement (Simplex PTM) at 0.1 wt% has been investigated. Resultant static and fatigue mechanical properties, in addition to thermal and polymerisation properties, have been determined. Significant improvements (p 0.001) in bending strength (42%), bending modulus (55%) and fracture toughness (22%) were demonstrated. Fatigue properties were improved (p 0.001), with mean number of cycles to failure and fatigue performance index being increased by 64% and 52%, respectively. Thermal necrosis index values at 44C and 55C were significantly reduced (p 0.001) (28% and 27%) versus the control. Furthermore, the onset of polymerisation increased by 58% (p < 0.001), as did the duration of the polymerisation reaction (52%). Peak energy during polymerisation increased by 672% (p < 0.001). Peak area of polymerisation increased by 116% (p < 0.001) indicating that the incorporation of MWCNT-COOH reduced the rate of polymerisation significantly. A non-significant reduction (8%) in percentage monomer conversion was also recorded. Raman spectroscopy clearly showed that the addition of MWCNT-COOH increased the ratio between normalised intensities of the G-Band and D-Band (IG/ID), and also increased the theoretical compressive strain (1.72%) exerted on the MWCNT-COOH by the Simplex PTM cement matrix. Therefore, demonstrating a level of chemical interactivity between the MWCNT-COOH and the Simplex PTM bone cement exists and consequently a more effective mechanism for successful transfer of mechanical load. The extent of homogenous dispersion of the MWCNT-COOH throughout the bone cement was determined using Raman mapping. Ke