Synthesis and electrochemical characterizations of nano-scaled Zn doped LiMn2O4 cathode materials for rechargeable lithium batteries

The LiZn_xMn_2−xO₄ (x = 0.00-0.15) cathode materials for rechargeable lithium-ion batteries were synthesized by simple sol-gel technique using aqueous solutions of metal nitrates and succinic acid as the chelating agent. The gel precursors of metal succinates were dried in vacuum oven for 10 h at 120 °C. After drying, the gel precursors were ground and heated at 900 °C. The structural characterization was carried out by X-ray powder diffraction and X-ray photoelectron spectroscopy to identify the valance state of Mn in the synthesized materials. The sample exhibited a well-defined spinel structure and the lattice parameter was linearly increased with increasing the Zn contents in LiZn_xMn_2−xO₄. Surface morphology and particle size of the synthesized materials were determined by scanning electron microscopy and transmission electron microscopy, respectively. Electrochemical properties were characterized for the assembled Li/LiZn_xMn_2−xO₄ coin type cells using galvanostatic charge/discharge studies at 0.5 C rate and cyclic voltammetry technique in the potential range between 2.75 and 4.5 V at a scan rate of 0.1 mV s⁻¹. Among them Zn doped spinel LiZn_0.10Mn_1.90O₄ has improved the structural stability, high reversible capacity and excellent electrochemical performance of rechargeable lithium batteries.     

Novel Foams Based on Freeze‐Dried Renewable Vital Wheat Gluten

A new way of producing rigid or semi‐rigid foams from vital wheat gluten using a freeze‐drying process is reported. Water/gluten‐based mixtures were frozen and freeze‐dried. Different foam structures were obtained by varying the mixing process and wheat gluten concentration, or by adding glycerol or bacterial cellulose nanofibers. MIP revealed that the foams had mainly an open porosity peaking at 93%. The average pore diameter ranged between 20 and 73 µm; the sample with the highest wheat gluten concentration and no plasticizer had the smallest pores. Immersion tests with limonene revealed that the foams rapidly soaked up the liquid. An especially interesting feature of the low‐wheat‐concentration foams was the “in situ” created soft‐top‐rigid‐bottom foams.

     

In situ synthesis of ammonia by catalytic hydrolysis of urea in the presence of aluminium oxide for safe use of ammonia in power plants for flue gas conditioning

BACKGROUND: Ammonia is applied to increase the efficiency of an electrostatic precipitator for fly ash removal from a flue gas stream from a boiler using fossil fuel. In the present work, the hydrolysis of urea to generate ammonia for flue gas conditioning, with the help of aluminium oxide catalyst, has been studied. RESULTS: The effect of temperature, catalyst and initial concentration on the conversion was studied. Conversion was found to increase exponentially with temperature. Addition of catalyst resulted in an increase in conversion. Experiments were conducted with different doses of catalyst, and the optimum dosage of catalyst for a particular feed concentration was determined. A decrease in conversion was observed when the initial concentration of ammonia was increased. CONCLUSION: A study of reaction kinetics showed the effect of reaction time on conversion of urea to ammonia. The catalytic hydrolysis of urea, using aluminium oxide behaved as a first‐order reaction; the rate constant at different temperatures was found, and the activation energy determined. Copyright © 2011 Society of Chemical Industry     

Conservative interpolation on unstructured polyhedral meshes: An extension of the supermesh approach to cell-centered finite-volume variables

A method is presented for conservatively transferring, or remapping, cell-centered variable fields from one mesh to another with second-order accuracy. The method is generally applicable to any polyhedral source or target mesh. Like the work of Farrell et al. [1], which was designed for finite-element computations, the proposed methodology uses a logical supermesh consisting of the intersections of polyhedra from both meshes. The resulting transfer process is well-suited for finite-volume methods that rely on cell-centered variables. The accuracy and efficacy of the new remapping process is demonstrated with numerical experiments and a computational fluid dynamics test.     

A systems engineering approach to validation of a pulmonary physiology simulator for clinical applications

Physiological simulators which are intended for use in clinical environments face harsh expectations from medical practitioners; they must cope with significant levels of uncertainty arising from non-measurable parameters, population heterogeneity and disease heterogeneity, and their validation must provide watertight proof of their applicability and reliability in the clinical arena. This paper describes a systems engineering framework for the validation of an in silico simulation model of pulmonary physiology. We combine explicit modelling of uncertainty/variability with advanced global optimization methods to demonstrate that the model predictions never deviate from physiologically plausible values for realistic levels of parametric uncertainty. The simulation model considered here has been designed to represent a dynamic in vivo cardiopulmonary state iterating through a mass-conserving set of equations based on established physiological principles and has been developed for a direct clinical application in an intensive-care environment. The approach to uncertainty modelling is adapted from the current best practice in the field of systems and control engineering, and a range of advanced optimization methods are employed to check the robustness of the model, including sequential quadratic programming, mesh-adaptive direct search and genetic algorithms. An overview of these methods and a comparison of their reliability and computational efficiency in comparison to statistical approaches such as Monte Carlo simulation are provided. The results of our study indicate that the simulator provides robust predictions of arterial gas pressures for all realistic ranges of model parameters, and also demonstrate the general applicability of the proposed approach to model validation for physiological simulation.     

Strontium-Doped Lanthanum Manganite Films Prepared by Magnetic Deposition

Deposition of La_0.85Sr_0.15MnO₃ (LSM) films from suspensions using a magnetic field was found to be a cheap and quick technique. Ninety weight percent of the particles present in the suspensions were deposited within the first minute of the deposition, and the thickness of the film varied linearly with the concentration of the suspension. Deposition phenomena were explained by modeling the magnetic flux in the deposition cell. Particles aligned with the flux lines, forming chains of LSM particles that, upon sintering, resulted in the formation of porous films with long chains of LSM grains.     

Developing a finite difference time domain parallel code for nuclear electromagnetic field Simulation

A two dimensional finite-difference time-domain code has been developed for complete simulation of nuclear electromagnetic pulse (NEMP) originating from an atmospheric nuclear detonation. The modules of NEMP simulation code describing various physics aspects are discussed. Typical results of the serial code for Compton current estimated from detailed neutron-gamma transport, induced air conductivity and electromagnetic fields are presented. The need for parallelizing such code has been explained. The parallel implementation using domain decomposition technique of message passing interface paradigm is described. The efficiency of the parallel code has been studied with increasing number of processors. The limitations of speed-up due to communication times are discussed.     

Broadband cylindrical dielectric resonator antenna excited by modified microstrip line

The impedance bandwidth of a high permittivity cylindrical dielectric resonator antenna excited by a microstrip line was significantly improved by modifying the feed geometry. The 10 dB return loss bandwidth is enhanced from 12 to 26% without much affecting the gain and other radiation properties of the antenna. Good agreement has been observed between the predicted and measured results.