Free boundary viscous flows at micro and mesolevel during liquid composites moulding process

Numerical simulation aspects, related to low Reynolds number free boundary viscous flows at micro and mesolevel during the resin impregnation stage of the liquid composite moulding process (LCM), are presented in this article. A free boundary program (FBP), developed by the authors, is used to track the movement of the resin front accurately by accounting for the surface tension effects at the boundary. Issues related to the global and local mass conservation (GMC and LMC) are identified and discussed. Unsuitable conditions for LMC and consequently GMC are uncovered at low capillary numbers, and hence a strategy for the numerical simulation of such flows is suggested. FBP encompasses a set of subroutines that are linked to modules in ANSYS. FBP can capture the void formation dynamics based on the analysis developed. We present resin impregnation dynamics in two dimensions. Extension to three dimensions is a subject for further research. Several examples are shown and efficiency of different stabilization techniques are compared. Copyright © 2004 John Wiley & Sons, Ltd.     

Determination of nickel in alloys and plant leaves with salicylaldehyde 3-oxobutanoylhydrazone by spectrophotometry.

A simple and highly sensitive reagent of salicylaldehyde 3-oxobutanoylhydrazone (salicylaldehyde acetoacetic acid hydrazone, SAAH) was synthesized and studied for the spectrophotometric determination of nickel in detail. In the pH range 6, which greatly increased the selectivity, nickel reacted with SAAH to form a 1:1 yellow complex, having a sensitive absorption peak at 405 nm. Under the optimal conditions, Beer's law was obeyed over the range from 0.0117 to 0.1174 microg cm(-3). The apparent molar absorptivity was 3.025 x 10(5) dm3 mol(-1) cm(-1). The detection limit and the variation coefficient were found to be 1.752 ng cm(-3) and 1.0%, respectively. The method has been applied to the quantitative determination of nickel in different alloys and leaves.     

Analysis and modeling for time-dependent behavior of polymers exhibited in nanoindentation tests

Through the arrangement of the applied load, experimental nanoindentation results of polymethylmethacrylate (PMMA) and polyurethane (PU) employed to establish a mechanical model. The proposed model consists of irreversible delayed plastic (viscoplastic) deformation, irreversible viscous deformation, and reversible delayed elastic (viscoelastic) deformations. The phase lag exhibited between the responding depth and the oscillating load is found to be linear proportional to frequency in the range of 1-50 Hz. The residual cavity profile of the PMMA scanned by an atomic force microscope gives a validity of accommodation assumption applied in the present model. The effects of overshooting, which occurred in the dwelling process, are also discussed.     

Vertical migration of 85Sr, 137Cs and 131I in various arable and undisturbed soils

The vertical migration of ⁸⁵Sr, ¹³⁷Cs and ¹³¹I in some arable and undisturbed single-contaminated soils was studied by gamma-spectrometry measurements under lysimetric laboratory conditions during irrigation of the soil profiles with wet atmospheric precipitation for about one year, except ¹³¹I. A new simple exponential compartment (box) model was derived, which makes it possible to calculate the migration rate constants and migration rates in the individual soil layers (vertical sections) as well as the total vertical migration rate constants and total vertical migration rates of radionuclides in the bulk soil horizon. The relaxation times of radionuclides in respective soil horizons can also be evaluated.     

Kinetic evidence of a common mechanism in the oxidations of diethyl sulfide by dichromates and halochromates of heterocyclic bases

The oxidations of diethyl sulfide by potassium dichromate, pyridinium dichromate, quinolinium dichromate, imidazolium dichromate, nicotinium dichromate, isonicotinium dichromate, pyridinium fluorochromate, quinolinium fluorochromate, imidazolium fluorochromate, pyridinium chlorochromate, quinolinium chlorochromate, and pyridinium bromochromate follow identical kinetic orders—first‐order each with respect to the chromium(VI) reagents, sulfide and hydrogen ion, and moderately inhibited by manganese(II) ion. The energy of activation varies linearly with the logarithm of frequency factor and so does the enthalpy of activation with the entropy of activation. Also, the activation free energies do not differ significantly. The dichromates and halochromates of heterocyclic bases oxidize diethyl sulfide via a common mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 1–8, 2003     

Block copolymer mediated synthesis of amphiphilic gold nanoparticles in water and an aqueous tetrahydrofuran medium: An approach for the preparation of polymer–gold nanocomposites

The synthesis of polymer‐matrix‐compatible amphiphilic gold (Au) nanoparticles with well‐defined triblock polymer poly[2‐(N,N‐dimethylamino)ethyl methacrylate]‐b‐poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] and diblock polymers poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate], polystyrene‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate], and poly(t‐butyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] in water and in aqueous tetrahydrofuran (tetrahydrofuran/H₂O = 20:1 v/v) at room temperature is reported. All these amphiphilic block copolymers were synthesized with atom transfer radical polymerization. The variations of the position of the plasmon resonance band and the core diameter of such block copolymer functionalized Au particles with the variation of the surface functionality, solvent, and molecular weight of the hydrophobic and hydrophilic parts of the block copolymers were systematically studied. Different types of polymer–Au nanocomposite films [poly(methyl methacrylate)–Au, poly(t‐butyl methacrylate)–Au, polystyrene–Au, poly(vinyl alcohol)–Au, and poly(vinyl pyrrolidone)–Au] were prepared through the blending of appropriate functionalized Au nanoparticles with the respective polymer matrices {e.g., blending poly[2‐(N,N‐dimethylamino)ethyl methacrylate]‐b‐poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate‐stabilized Au with the poly(methyl methacrylate)matrix only}. The compatibility of specific block copolymer modified Au nanoparticles with a specific homopolymer matrix was determined by a combination of ultraviolet–visible spectroscopy, transmission electron microscopy, and differential scanning calorimetry analyses. The facile formation of polymer–Au nanocomposites with a specific block copolymer stabilized Au particle was attributed to the good compatibility of block copolymer coated Au particles with a specific polymer matrix. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1841–1854, 2006     

Gravimetric separation of titanium and zirconium from Niobium with Phenylacetylhydroxamic acid

Phenylacetylhydroxamic acid is used to separate titanium and zirconium from niobium in an oxalate medium at pH 6.5–7.5 in presence of ammonium chloride at room temperature. The method is accurate when the ratio of (TiO₂ + ZrO₂) : Nb₂O₅ is 10 : 1 to 1 : 1 ; when the niobium concentration is higher, reprecipitation is necessary. Tantalum, citrate, tartrate, lactic acid, EDTA, and a large excess of oxalate interfere.     

On the photometric determination of trivalent rhodium with eriochromecyanine RC

Summary Eriochromecyanine RC has been used as chromogenic reagent for the photometric determination of rhodium(III) on a micro scale. A coloured Rh(III)-ECRC chelate with _max 530 nm at pH 4.0 (25°C) is formed. A detailed study has been made concerning to characteristics, composition and stability of the chelate. Standard deviation was ±1.17%.

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Über die photometrische Bestimmung von dreiwertigem Rhodium mit Eriochromcyanin RC

Zusammenfassung Ergebnisse einer Untersuchung über die Zusammensetzung und Stabilität des Komplexes werden mitgeteilt. Das Absorptionsmaximum liegt bei 530 nm (pH 4,0; 25°C). Bestimmungen konnten mit einer Standardabweichung von ±1,17% durchgeführt werden.

     

Semiclassical statistical mechanics of two-dimensional hard-body fluids

The problem of calculating the thermodynamic properties of two-dimensional semiclassical hard-body fluids is studied. Explicit expressions are given for the first-order quantum corrections to the free energy, equation of state, and virial coefficients. The numerical results are calculated for the planar hard dumbbell fluid. Significant features are the increase in quantum corrections with increasing eta and increasing L*=L/sigma(0).