Numerische Strömungssimulation an einer Niedergeschwindigkeits-Axialturbine unterschiedlichen Deckband-Abschirmungen des Laufrades

The numerical simulation of the flow through a low-speed turbine stage followed by a vane row is presented for two experimentally investigated shrouds of different weight and shape. The aerofoil-pressure distribution of the blades and vanes as well as the flow at the exit of the bladerow is compared in the experimentally and numerically obtained results. In addition to experimental data published earlier, numerical flow results are added, which had been inaccessible in the experiment. The choice of the turbulence model influences substantially the result of the numerical simulation for the flow leaving the rotor blade row. Furthermore the computational result shows the influence of the flow pattern in the labyrinth cavity on the power loss. The prediction of the static pressure decrease along the flow path through the seal across the cavities concludes this investigation.     

Capacity allocation problem in flexible manufacturing systems: branch and bound based approaches

This study considers an operation assignment and capacity allocation problem that arises in flexible manufacturing systems. The machines have limited time and tool magazine capacities and the available tools are limited. Our objective is to maximise total weight of assigned operations. We develop a branch and bound algorithm that finds the optimal solutions and a beam search algorithm that finds high quality solutions in polynomial time.     

Synthesis of hydroxyapatite crystals using carboxymethyl inulin for use as a delivery of ibuprofen

In the present study biodegradable, environmentally friendly polysaccharide-based polycarboxylate, carboxymethyl inulin (CMI), was used to produce hydroxyapatite (HAP) particles by wet chemical synthesis under controlled temperature, pH, and atmospheric conditions. The morphology and microstructure of the HAP nanoparticles were investigated by XRD, SEM, DTA–TGA and FTIR. CMI affects morphology, surface area, dimension and particle size distribution of the crystals. The reduction in size is greater in the direction of the c-axis. The increase in the polymer concentration to 7.5 g/L resulted in the mixture of nanoparticles with particle sizes of less than 100 nm. The SEM micrograph shows the formation of well-crystallized, agglomerated small particles of HAP. X-ray analysis has shown that the resulting particles have high thermal stability.The obtained crystals were used to produce tablets by direct compression of HAP. The influence of sample's CMI concentration on drug release profiles was investigated by using ibuprofen (C₁₃H₁₈O₂) as a model drug. The model was used to determine the effective diffusion coefficient of the drug from the tablets. A good agreement between experimental data and model predictions was obtained as calculated in the present work. The values of the diffusion coefficients range from 1.62 × 10^? 7 to 4.72 × 10^? 7 m² h^? 1.     

Preparation,characterization and pharmacokinetic evaluation of rosuvastatin calcium incorporated cyclodextrin-polyanhydride nanoparticles

Abstract

Objective: The aim of the study was to formulate, cyclodextrin (CD)-polyanhydride (PA) nanoparticles (CPNs) with rosuvastatin calcium (RCa) in order to enhance the poor oral bioavailability.

Methods: CPNs containing RCa/CD complexes were prepared by a modified solvent displacement method and morphological analyses, particle size (PS), polydispersity index (PDI), zeta potential (ZP), encapsulation efficiency (EE), DSC, FT-IR, XRD, ¹H-NMR analyses were performed. In vitro release properties, release kinetics, cytotoxicity, in vitro permeability and pharmacokinetic studies were also studied. The stability of the formulations were evaluated during the storage period of 3?months.

Results: The physicochemical studies showed that the RCa/CD complexes were well incorporated into CPNs resulted in nanosized particles (215.22 and 189.13?nm) with homogenous size distribution (PDI: 0.203 and 0.182) with relatively high incorporation capacity (76.11 and 68.18%) for the CPN1 and CPN2 formulations respectively. Sustained release of RCa from CPNs were achieved. The cytotoxicity values showed that the safety of the formulations. According to permeability studies, pure RCa had lowest permeability data (3.08?×?10^?7?cm?s^?1 P_app value) while CPNs gained higher permeability data (1.36?×?10^?5 and 1.12?×?10^?5?cm?s^?1 P_app values) for the CPN1 and CPN2 formulations respectively. CPN2 formulation was selected for pharmacokinetic studies and analyses results demonstrated that approximately 8-fold relative oral bioavailability enhancement compared to the pure RCa was achieved.

Conclusion: Considering the analyses results of the study, CPNs can be regarded as suitable, safe, functional oral delivery systems for RCa with enhanced oral bioavailability.     

On diffraction of waves by the infinite grating of circular dielectric cylinders at oblique incidence: Floquet representation

Abstract

We investigate the diffraction of plane E-polarized electromagnetic waves by an infinite array of infinitely long circular dielectric cylinders for the most generalized case of oblique incidence. Employing the Sommerfeld integral representation of the Hankel function, and exploiting Poisson's summation formula in separation-of-variables solution, we have acquired a new representation for the diffraction of waves by the infinite grating of the circular dielectric cylinders at oblique incidence. The exact solutions for the external electric and magnetic field intensities have been derived in terms of the diffraction angles of the grating which are obtained by solving the grating equation. In addition, the transmitted and reflected fields of the infinite grating have been presented in terms of propagating and evanescent Floquet modes.     

Kinetics of mercury ions removal from synthetic aqueous solutions using by novel magnetic p(GMA-MMA-EGDMA) beads

Poly(glycidylmethacrylate-methylmethacrylate), p(GMA-MMA-EGDMA), magnetic beads were prepared via suspension polymerization in the presence of ferric ions. The epoxy groups of the beads were converted into amino groups via ring opening reaction of the ammonia and, the aminated magnetic beads were used for the removal of Hg(II) ions from aqueous solution in a batch experiment and in a magnetically stabilized fluidized bed reactor (MFB). The magnetic p(GMA-MMA-EGDMA) beads were characterized with scanning electron microscope (SEM), FT-IR and ESR spectrophotometers. The optimum removal of Hg(II) ions was observed at pH 5.5. The maximum adsorption capacity of Hg(II) ions by using the magnetic beads was 124.8+/-2.1 mgg(-1) beads. In the continuous MFB reactor, Hg(II) ions adsorption capacity of the magnetic beads decreased with an increase in the flow-rate. The maximum adsorption capacity of the magnetic beads in the MFB reactor was 139.4+/-1.4 mgg(-1). The results indicate that the magnetic beads are promising for use in MFB for removal of Hg(II) ions from aqueous solution and/or waste water treatment.     

Bi(III)4-methylpiperidinedithiocarbamate coprecipitation procedure for separation--pre-concentration of trace metal ions in water samples by flame atomic absorption spectrometric determination

A pre-concentration method was developed for determination of trace amounts of cadmium, copper and lead in water samples by FAAS after coprecipitation by using potassium 4-methylpiperidinedithiocarbamate (K4-MPDC) as a chelating agent and Bi(III) as a carrier element. This procedure is based on filtration of the solution containing precipitate on a cellulose nitrate membrane filter following Cd(II), Cu(II) and Pb(II) coprecipitation with Bi(III)4-MPDC and then the precipitates together with membrane filter were dissolved in concentrated nitric acid. The metal contents of the final solution were determined by FAAS. Several parameters including pH of sample solution, amount of carrier element and reagent, standing time, sample volume for precipitation and the effects of diverse ions were examined. The accuracy of the method was tested with standard reference material (MBH, C31XB20 and CRM BCR-32) and Cd, Cu and Pb added samples. Determination of Cd, Cu and Pb was carried out in sea water, river water and tap water samples. The recoveries were >95%. The relative standard deviations of determination were less than 10%.     

Constitutive modeling of two phase materials using the mean field method for homogenization

A Mean-Field homogenization framework for constitutive modeling of materials involving two distinct elastic-plastic phases is presented. With this approach it is possible to compute the macroscopic mechanical behavior of this type of materials based on the constitutive models of the constituent phases. Different homogenization schemes that exist in the literature are implemented in efficient algorithms to be used in full-scale FE simulations. These schemes are compared with each other in terms of efficiency. Additionally two new schemes are proposed which are both computationally efficient and compare in accuracy with the more physically based approaches. Finally the algorithms are demonstrated on FE simulations of sheet metal forming operations and compared with experimental results.     

Hydroxyapatite containing superporous hydrogel composites: synthesis and in-vitro characterization

The synthesis of an acrylamide-based superporous hydrogel composite (SPHC) with hydroxyapatite (HA) was realized by solution polymerization technique. The characterization studies were performed by FTIR studies, determination of swelling kinetics, measurement of mechanical properties, SEM/EDAX studies and cytocompatibility tests. The FTIR and EDAX studies revealed the incorporation of HA in superporous hydrogel (SPH) structure. The results obtained from swelling experiments showed that, although the extent of swelling was decreased after incorporation of HA in SPH structure, the time to reach the equilibrium swelling was not affected for SPHC. This result indicated that, the presence of HA did not block the capillary channels and the interconnected pore structure was maintained which were consistent with the images obtained from SEM photographs. The results obtained from mechanical tests showed that, in the presence of HA, the compression strength of the hydrogel composite was improved significantly when compared to SPH structure. The compressive modulus for the SPHC increased to 6.59 ± 0.35 N/mm² whereas it was 0.63 ± 0.04 N/mm² for the SPH. The cytocompatibility test which was performed by using L929 fibroblasts showed that both the SPH and SPHC materials were cytocompatible towards fibroblasts. The synthesized superporous hydrogel composite possesses suitable properties especially for bone tissue engineering applications and shall be considered as a novel scaffold.     

On the linear complexity profile of nonlinear congruential pseudorandom number generators of higher orders

Nonlinear congruential methods are attractive alternatives to the classical linear congruential method for pseudorandom number generation. Generators of higher orders are of interest since they admit longer periods. We obtain lower bounds on the linear complexity profile of nonlinear pseudorandom number generators of higher orders. The results have applications in cryptography and in quasi-Monte Carlo methods.