Computation of cascade flutter by uncoupled and coupled methods

A computational method for flutter prediction of turbomachinery cascades is presented. The flow through multiple blade passages is calculated using a time-domain approach with coupled aerodynamic and structural models. The unsteady Euler/Navier-Stokes equations are solved in quasi-three-dimensions using a second-order implicit scheme with dual time-stepping and a multigrid method. A structural model for the blades with bending and torsion degrees of freedom is integrated in time together with the flow field. Information between structural and aerodynamic models is exchanged until convergence in each real-time step. Computational results for a cascade are presented and compared with those obtained by the conventional energy method and with experimental and numerical data by other authors. Significant differences are found between the coupled and uncoupled methods at low mass ratios. A transonic test case with strong nonlinear phenomena is investigated with the fluid-structure coupled method. Results for inviscid flow are compared with results of Navier-Stokes computations.     

Nonlinear tunneling of optical soliton in 3 coupled NLS equation with symbolic computation

We investigated the soliton solution for N$N$ coupled nonlinear Schrödinger (CNLS) equations. These equations are coupled due to the cross-phase-modulation (CPM). Lax pair of this system is obtained via the Ablowitz–Kaup–Newell–Segur (AKNS) scheme and the corresponding Darboux transformation is constructed to derive the soliton solution. One and two soliton solutions are generated. Using two soliton solutions of 3 CNLS equation, nonlinear tunneling of soliton for both with and without exponential background has been discussed. Finally cascade compression of optical soliton through multi-nonlinear barrier has been discussed. The obtained results may have promising applications in all-optical devices based on optical solitons, study of soliton propagation in birefringence fiber systems and optical soliton with distributed dispersion and nonlinearity management.     

Nucleation kinetics,growth and hardness parameters of l-alanine alaninium picrate (LAAP) single crystals

Amino acids are considered to be the building blocks of proteins and are gaining importance due to their interesting optical behavior. l-alanine is an amino acid which dissolves in water and it can react with other acids to form new compounds. In this work, l-alanine is mixed with picric acid to prepare l-alanine alaninium picrate (LAAP) salt. Solubility and metastable zone width were measured for LAAP salt and induction period was measured at different supersaturation ratios. The critical nucleation parameters were evaluated based on the classical theory of homogeneous nucleation. Using the optimized nucleation parameters, single crystals of LAAP salt were grown by slow evaporation technique. XRD and FTIR studies were carried out to understand structural and molecular formation of the crystal. Microhardness measurements were performed on the grown LAAP crystal and various parameters such as work hardening constant, stiffness constant, yield strength, resistance pressure and corrected hardness were evaluated. Nonlinear optical behavior of the sample was analyzed.     

Stable-isotope dilution GC-MS method for ethanol in vapour ethanol and microdialysis systems based on carbonate-catalyzed extractive pentafluorobenzoylation

Common ethanol detection methods are not applicable to cell culture media and microdialysates due to interference with medium constituents including amino acids and pH indicators. We present a novel GC-MS method for the accurate and precise analysis of ethanol in cell cultures and microdialysates. The method is based on the carbonate-catalyzed extractive pentafluorobenzoylation of ethanol and deuterium-labelled ethanol serving as the internal standard and on their GC-MS analysis in the electron-capture negative-ion chemical ionization mode. The method was used to optimize experimental conditions in a custom-made ethanol vapour system utilized for studies examining ethanol influences on neuronal cell lines and in microdialysis.     

A study on the influence of dysprosium cation substitution on the structural, morphological, and electrochemical properties of lithium manganese oxide

The synthesis of series of dysprosium-doped lithium manganese oxide in the general formula LiDy _x Mn_2?x O4 (x?=?0.0, 0.05, 0.1, 0.15, and 0.2) using double stage coprecipitation method followed by microwave heat treatment is reported. The characterization results of X-ray diffraction and infrared spectroscopy have illustrated the cubic structure for all the compounds. The lattice parameter has been observed to decrease with dysprosium doping. The influence of doping in elastic property of the samples has been studied with infrared spectroscopy. The grain size of the LiDy_0.05Mn_1.95O₄ has been observed to be less than 1???m. The Image J software has been used to further analyze the micrographs. The initial capacity of the samples are observed to decrease with Dy³⁺ doping, but the capacity retention after 50 cycles for Dy 0.05, 0.1, 0.15, and 0.2 samples are reported as 95.4%, 93.2%, 91.3%, and 87.7%, respectively. The electrochemical impedance spectra has been performed to analyze the effectiveness of Dy³⁺ ion doping and the act of Dy doping has been observed to reduce the charge transfer resistance and increase the Li ion diffusion coefficient.     

Tunable energy transfer distributed feedback dye laser using pyronin B and crystal violet dye mixture

Using pyronin B and crystal violet dye mixture, the characteristics of energy transfer distributed feedback dye laser (ETDFDL) pumped by 532 nm Nd:YAG laser were investigated. The characteristics of donor DFDL and acceptor DFDL as well as the dependence of their pulse widths and output powers on pump power and acceptor concentrations were studied. The output energy of DFDL was measured at the emission peaks of donor and acceptor dyes for different pump powers and acceptor concentrations, and tunability was observed from 570 to 645 nm using prism dye cell arrangement.     

Inductive Construction of the Loop Transform for Abelian Gauge Theories

We construct the loop transform in the case of Abelian gauge theories as a unitary operator given by the inductive limit of Fourier transforms on tori. We also show that its range, i.e. the space of kinematical states of the quantum loop representation, is the Hilbert space of square integrable complex valued functions on the group of hoops.     

Synthesis and characterization of starch-graft-polycaprolactone as compatibilizer for starch/polycarprolactone blends

Polycaprolactone (PCL) was grafted onto starch through introduction of urethane linkages. The grafting reaction was carried out in two steps. The first step was the reaction of hydroxyl-terminated PCL with 2,4-tolylene diisocyanate. The isocyanate terminated PCL was then reacted with starch to obtain starch-graft-polycaprolactone (starch-g-PCL). The grafting reaction was confirmed by FT-IR spectroscopy. The compatibility of the starch/PCL blend was enhanced with a compatibilizer, starch-g-PCL, whose amount was 3 wt.-% of the blend. The tensile strength and morphology of the compatibilized blend were determined. It was found that the compatibilized starch/PCL blend has finer phase domains and an improved interfacial adhesion. Mechanical properties of the compatibilized blend were found to be significantly higher than those of the corresponding uncompatibilized starch/PCL blend.     

Functionalization of polyesters with maleic anhydride by reactive extrusion

Maleic anhydride (MAn) was grafted onto aliphatic and aromatic/aliphatic copolyesters by reactive extrusion in the presence of a free radical initiator using a twin‐screw extruder. The grafting reaction was confirmed by spectroscopic analyses. The presence of succinic anhydride groups was shown by FT‐IR spectroscopy, and NMR spectra indicate that the grafts consist of single succinic anhydride units. The 2D ¹H‐NMR spectra (COSY) indicate that grafting reactions take place at aliphatic dicarboxylic acid units of copolyesters. The graft content was determined by a nonaqueous titration method. The effects of concentration of initiator and monomer and reaction temperature on the graft content and intrinsic viscosity were studied. The low percentage grafting in poly(lactic acid) was observed due to the presence of limited free radical sites in the polymer backbone. Temperature and monomer and initiator concentrations affect the graft content, and the desired graft content with minimal degradation can be obtained by controlling these factors. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1693–1702, 1999