Effect of coefficient of restitution in Euler-Euler CFD simulation of fluidized-bed hydrodynamics

Collision between particles plays an important role in determining the hydrodynamic characteristics of gas-solid flow in a fluidized bed.In the present work,earlier work(Loha,Chattopadhyay. Chatterjee,2013) was extended to study the effect of the elasticity of particle collision on the hydrodynamic behavior of a bubbling fluidized bed filled with 530-μm particles.The Eulerian-Eulerian two-fluid model was used to simulate the hydrodynamics of the bubbling fluidized bed.where the solid-phase properties were calculated by applying the kinetic theory of granular flow.To investigate the effect of the elasticity of particle collision,different values of the coefficient of restitution were applied in the simulation and their effects were studied in detail.Simulations were performed for two different solid-phase wall boundary conditions.No bubble formation was observed for perfectly elastic collision.The bubble formation started as soon as the coefficient of restitution was set below 1.0,and the space occupied by bubbles in the bed increased with a decrease in the coefficient of restitution.Simulation results were also compared with experimental data available in the literature,and good agreement was found for coefficients of restitution of 0.95 and 0.99.     

Finite element analysis of the demagnetization effect and stress inhomogeneities in magnetic shape memory alloy samples

This paper is concerned with the finite element analysis of boundary value problems involving nonlinear magnetic shape memory behavior, as might be encountered in experimental testing or engineering applications of magnetic shape memory alloys (MSMAs). These investigations mainly focus on two aspects: first, nonlinear magnetostatic analysis, in which the nonlinear magnetic properties of the MSMA are predicted by the phenomenological internal variable model previously developed by Kiefer and Lagoudas, is utilized to investigate the influence of the demagnetization effect on the interpretation of experimental measurements. An iterative procedure is proposed to deduce the true constitutive behavior of MSMAs from experimental data that typically reflect the shape-dependent system response of a sample. Secondly, the common assumption of a homogeneous Cauchy stress distribution in the MSMA sample is tested. This is motivated by the expectation that the influence of magnetic body forces and body couples caused by field matter interactions may not be negligible in MSMAs that exhibit blocking stresses of well below 10?MPa. To this end, inhomogeneous Maxwell stress distributions are first computed in a post-processing step, based on the magnetic field and magnetization distributions obtained in the magnetostatic analysis. Since the computed Maxwell stress fields, though allowing a first estimation of the influence of the magnetic force and couple, do not satisfy equilibrium conditions, a finite element analysis of the coupled field equations is performed in a second step to complete the study. It is found that highly non-uniform Cauchy stress distributions result under the influence of magnetic body forces and couples, with magnitudes of the stress components comparable to externally applied bias stress levels.     

A terpyridyl-imidazole (tpy-HImzPh3) based bifunctional receptor for multichannel detection of Fe2+ and F- ions

The X-ray crystal structures of the tridentate ligand, 4'-[4-(4,5-diphenyl-1H-imidazol-2-yl)-phenyl]-[2,2':6',2']terpyridine (tpy-HImzPh(3)) and its bis-homoleptic iron(ii) complex of composition [Fe(tpy-HImzPh(3))(2)](2+) have been determined, showing that the ligand crystallized in a monoclinic form with the space group P2(1)/c while its Fe(II) complex crystallizes in an orthorhombic form with space group Fddd. Both the anion and cation binding properties of the receptor were thoroughly investigated in dimethylformamide-acetonitrile (1?:?9) solution using absorption, emission, and (1)H NMR spectral studies which revealed that the receptor acts as a sensor for both F(-) and Fe(2+). In the presence of excess F(-) ion, deprotonation of the imidazole N-H fragment of the receptor occurs, an event which is signaled by the development of a yellow color visible with the naked eye. The estimated value of the equilibrium constant of the receptor with F(-) is 1.9 × 10(4) M(-1). Deprotonation is also observed in the presence of hydroxide. The receptor also shows colorimetric and fluorimetric sensing ability towards Fe(2+) ions. The binding site for the metal ion in the system has been unambiguously established by single-crystal X-ray diffraction studies of the Fe(II) complex of the receptor. The influence of solvents on the absorption and fluorescence spectra of the receptor has been investigated in detail. Cyclic voltammetric (CV) and square wave voltammetric (SWV) measurements carried out in dimethylformamide-acetonitrile (2?:?3) provided evidence in favor of cation (Fe(2+)) and anion (F(-)) concentration dependent electrochemical responses, enabling the ligand to act as a suitable electrochemical sensor for F(-) and Fe(2+) ions.     

Immobilization of poly(fluorene) within clay nanocomposite: an easy way to control keto defect

Blue light emitting cationic polyfluorene polymer(PF)/montmorillonite (MMT) nanocomposites were prepared by solution intercalation and exfoliation method to evaluate the effect of MMT on the nanocomposite structures, properties and morphologies. The properties of PF-MMT composites, containing 1-50 mass% MMT, were characterized unambiguously with the help of multiple analytical techniques, with focus on the keto defect and photostability of PF in the nanocomposites. XRD and HRTEM studies reveal both exfoliation of MMT galleries at lower content of MMT in composites and intercalation of PF chains into the MMT galleries at higher MMT content. The nanocomposites show higher thermal stability than pristine PF as anchorage of nanoclay in PF matrix occur through the electrostatic interaction between nanoclay and polymer. The decrease in Si-O-Si stretching frequency during exfoliation is much higher than in intercalation, as Si-O-Si experience lesser hindrance to vibrate in exfoliated MMT galleries. The gradual redshift of π-π(*) transition peak of PF with increasing MMT content in composites confirms the uncoiling of PF in clay galleries. The photoluminescence characteristics reveal interruption of interchain interaction in this intercalated and exfoliated organic/inorganic hybrid system, which reduces the low-energy emission that results from keto defect. Due to very high aspect ratio of MMT, it can act as an efficient exciton blocking layer and a barrier to oxygen diffusion, which may lead to a device with high color purity and enhanced photostability. Again current-voltage characteristics of nanocomposite films confirm the retention of LED properties after nanocomposite formation.     

Antitumour activity of Terminalia arjuna leaf against Ehrlich ascites carcinoma in mice

Terminalia arjuna Roxb. (Combretaceae), commonly known as 'Arjuna', is a large tree occurring throughout the Indian peninsula. This study was undertaken to evaluate the methanol extract of T. arjuna leaf (META) for antitumour activity against Ehrlich ascites carcinoma (EAC) in Swiss albino mice. Twenty-four hours after intraperitonial inoculation of tumour (EAC) cells in mice, META was administered at 100 and 200?mg?kg(-1) body weights for 9 consecutive days. On day 10, half of the mice were sacrificed and the rest kept alive for an assessment of the increase in life span. The antitumour effect of META was assessed by evaluating tumour volume, tumour weight, viable and non-viable tumour cell counts, median survival time and increase in life span of EAC-bearing hosts. Haematological profiles were estimated. META showed a significant (p<0.001) decrease in tumour volume, tumour weight and viable cell count, and also increased the life span of EAC-bearing mice. Haematological profiles were significantly (p<0.001) restored to normal levels in META-treated mice compared to the EAC control. Therefore, from this study, it can be concluded that T. arjuna leaf exhibited remarkable antitumour activity against EAC in Swiss mice.     

Heat Transfer from a Hot Moving Steel Plate by Air-Atomized Spray Impingement

Air-atomized spray cooling of a hot moving AISI 304 steel plate of 6 mm thickness has been investigated experimentally by varying water flow rate and plate velocity at a fixed nozzle-to-plate distance. It is found that the heat transfer coefficient is a non-linear function of surface temperature. The result shows that the cooling rate increases with an increase in the water flow rate. The highest cooling rate has been found for the static plate, whereas for a moving plate, an increasing cooling rate trend has been observed with increasing plate velocity.     

A newly developed highly selective ratiometric fluoride ion sensor: spectroscopic, NMR and density functional studies

A new easy-to-synthesize chemosensor, 3,3'-bis(indolyl)-4-chlorophenylmethane (hereafter S), was designed, synthesized and employed as a selective optical chemosensor for fluoride ions.(1)H NMR and density functional studies on the system have been carried out to determine the nature of the interaction between S and X(-) (X = inorganic anions) responsible for the significant fluoride-induced changes in the absorption properties of S. The experimental results reveal that abstraction of an acidic proton of S by the fluoride ion, leading to the formation of anionic species, is responsible for the spectral changes. These changes allow signaling for the fluoride ion to detect and estimate the concentration of fluoride ion present even at the submicromolar level, accurate up to 2 μM. Calculations of the transition energies of S, S(-), and S···F(-) (hydrogen bonded complex) show that only S(-) is responsible for the long-wavelength absorption band in the presence of F(-).     

Effect of ex-situ hydrogen passivation on the structural properties of e-beam evaporated amorphous silicon thin film for solar cell applications

Thin-film photovoltaics greatly reduce the semiconductor material content in the finished product, using 150–200 times less material as compared with conventional Si wafer based cells. Electron beam evaporation (e-beam), a non-ultra-high vacuum technique has the potential for being inexpensive, and simpler process for a-Si deposition. It offers specific advantages such as high Si deposition rate (up to 1 μm/min), excellent Si source material usage, avoidance of toxic gases, and simple sample preparation conditions. In this work, we report the growth of a-Si films using e-beam at a growth rate exceeding 30 Å/s (1–5 Å/s for conventional PECVD process). We report the effect of hydrogen passivation on amorphous silicon network and on silicon-bonded hydrogen configuration under ex-situ hydrogenation in hydrogen plasma. The hydrogen concentration and silicon-hydrogen bonding configuration was evaluated using nuclear reaction analysis (NRA) and Fourier transform infrared spectroscopy (FTIR). Hydrogen plasma treatment shows an increase in the monohydride bond concentration with substrate temperature, and is corroborated by our FTIR investigation, in addition to reducing clustered monohydride bonds or polyhydride bonds in a-Si:H film. Raman analysis indicates reduction in silicon bond angle as well as the bond distance, both leading to significant structural improvement in short-range and medium range order in the amorphous phase. Thus, ex-situ hydrogenation clearly demonstrates the possibility of comparable hydrogen passivation in e‐beam evaporated a-Si films with high growth rate. One can easily extrapolate this result to microcrystalline film growth, assuming the structural improvement of the silicon network preceding the microcrystalline nucleation, where ex-situ passivation is most effective. Thus ex-situ hydrogenation opens up new possibilities in minutely tailoring the a:Si film properties especially for solar cell applications.     

Exciplex formation and energy transfer in a self-assembled metal-organic hybrid system

Exciting assemblies: A metal-organic self-assembly of pyrenebutyric acid (PBA), 1,10-phenanthroline (o-phen), and Mg(II) shows solid-state fluorescence originating from a 1:1 PBA-o-phen exciplex. This exciplex fluorescence is sensitized by another residual PBA chromophore through an excited-state energy-transfer process. The solvent polarity modulates the self-assembly and the corresponding exciplex as well as the energy transfer, resulting in tunable emission of the hybrid (see figure).     

Supersymmetric Isospectral Formalism for the Calculation of Near-Zero Energy States: Application to the Very Weakly Bound 4He Trimer Excited State

We propose a novel mathematical approach for the calculation of near-zero energy states by solving potentials which are isospectral with the original one. For any potential, families of strictly isospectral potentials (with very different shape) having desirable and adjustable features are generated by supersymmetric isospectral formalism. The near-zero energy Efimov state in the original potential is effectively trapped in the deep well of the isospectral family and facilitates more accurate calculation of the Efimov state. Application to the first excited state in ⁴He trimer is presented.