Robustness testing of control charts employed by analytical laboratories

 The robustness of Shewhart control charts for subgroup means and subgroup ranges was tested by using the Monte Carlo method using training data sets comprising various numbers of points, with two repetitions in each subgroup (as in routine laboratory practice). The following control chart designs were tested: conventional based on the arithmetic mean and standard deviation, robust based on the median and/or the trimmed mean and Winsorized standard deviation, and a two-step design. The methods were applied to the system in the state of statistical control (outliers excluded) and to the system without statistical control (outliers included). Satisfactory results for both cases were only obtained when using the two-stage control charts. The conventional charts led to underestimation of the effect of outliers in the system without statistical control, whereas the robust control charts led to overestimation of the effect of outliers (false alarm) in the system under statistical control. The tests also gave evidence that the training set should include 20 points as a minimum. Received: 13 January 1997 Accepted: 12 February 1997     

Vapour—liquid equilibrium at elevated pressures from the perturbation theory. II. Binary systems

Vapour—liquid equilibria in binary systems of non-polar non-spherical molecule compounds were studied theoretically by combining the perturbation theory of convex molecule fluids with a new variant of the conformal solution theory. The recently proposed equation of state of hard convex body mixtures and the corresponding expressions for the contact values of distribution functions were employed to determine the reference thermodynamic functions and the perturbation terms. Ten binary systems, i.e. ArCH₄, N₂CH₄, N₂C₂H₄, N₂C₂H₆, CH₄C₂H₄, CH₄C₂H₆, C₂H₄C₂H₆, CO₂C₂H₄, CO₂C₂H₆, and ArCO₂ were studied at constant temperatures. Comparison of theoretical predictions with experimental data is given.     

Electronic spectra of ferrocenyl chalcones

The electronic absorption spectra of two series of ferrocenyl chalcones (Fc-CH=CH-CO-Ar,1 andFc-CO-CH=CH-Ar,2) in methanol andn-hexane were recorded. Excellent correlations of _max of the d-d transition between 450–540 nm withHammett substituent constants were found in1, and reasonable correlations in2. In methanol a bathochromic shift of this band occurs. An explanation of this phenomenon, partially based on ligand field calculations, is presented.

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Elektronenabsorptions-Spektren von Ferrocenylchalkonen. Zur Substituentenabhängigkeit von _max des d-d-Überganges

Zusammenfassung Die Elektronenabsorptions-Spektren von zwei Reihen von Ferrocenylchalkonen (Fc-CH=CH-CO-Ar,1 undFc-CO-CH=CH-Ar,2) wurden in Methanol undn-Hexan gemessen. Für1 wurde eine ausgezeichnete Übereinstimmung der _max-Werte des d-d-Überganges (zwischen 450 und 540 nm) mit denHammett-Substituentenkonstanten gefunden, während sie in der Reihe2 befriedigend ist. In Methanol erleidet die genannte Bande eine bathochrome Verschiebung.Eine Erklärung für diese Ergebnisse wird präsentiert, die zum Teil auf Ligandenfeld-Berechnungen basiert.

     

Thermal properties of oxide glasses

A criterion based on the length of induction period of crystallization was used to study the effect of added CoO and NiO oxides on the thermal stability of Li₂O·2SiO₂ glass system against crystallization. It was found out that the thermal stability of studied glasses against crystallization is Li₂O·2SiO₂ < Li₂O·2SiO₂·0.1CoO < Li₂O·2SiO₂·0.1NiO. The addition of CoO and NiO oxides to Li₂O·2SiO₂ glass system increases its thermal stability. These results coincide with the order determined by stability criteria based on the characteristic temperatures.     

Structure changes of electrorheological fluids based on polyaniline particles with various hydrophilicities and time dependence of shear stress and conductivity during flow

Particles of polyaniline protonated with perfluorooctanesulfonic acid provided a material with hydrophobic surface. This property enabled its perfect dispersion in silicone oil due to its good compatibility with the hydrophobic medium. In contrast, in a suspension of hydrophilic polyaniline particles doped with sulfamic acid, strong interactions of particles prevailed, which led to the formation of entangled chains of aggregated particles in suspension. The difference in structural properties of suspensions exists already in the absence of electric field and significantly influences their electrorheological behavior after application of electric field. The formation of electrorheological structure has been monitored by recording time dependences of the shear stress and the electric current passing through the flowing suspensions.     

Electrorheological properties of suspensions of hollow globular titanium oxide/polypyrrole particles

Hollow globular clusters of titanium oxide (TiO₂) nanoparticles were synthesized by a simple hydrothermal method. The prepared particles were consequently coated by in situ polymerization of conductive polymer polypyrrole (PPy) to obtain novel core–shell structured particles as a dispersed phase in electrorheological (ER) suspensions. The X-ray diffraction analysis and scanning electron microscopy provided information on particle composition and morphology. It appeared that PPy coating improved the compatibility of dispersed particles with silicone oil which results in higher sedimentation stability compared to that of mere TiO₂ particles-based ER suspension. The ER properties were investigated under both steady and oscillatory shears. It was found that TiO₂/PPy particles-based suspension showed higher ER activity than that of mere TiO₂ hollow globular clusters. These observations were elucidated well in view of their dielectric spectra analysis; a larger dielectric loss enhancement and faster interfacial polarization were responsible for a higher ER activity of core–shell structured TiO₂/PPy-based suspensions. Investigation of changes in ER properties of prepared suspensions as a function of particles concentration, viscosity of silicone oil used as a suspension medium, and electric field strength applied was also performed.     

Electrorheological properties of hydrolyzed poly(glycidyl methacrylate) suspensions

 Electrorheological behavior of silicone oil suspensions of macroporous poly[(glycidyl methacrylate)-co-(ethylene dimethacrylate)]) (0.60 : 0.40 w) hydrolyzed to various degrees was investigated. Polarizability of particles expressed by the particle dipole coefficient and, consequently, pseudoplasticity of the system at low shear rates after application of an external electric field steeply increased with the hydrolysis degree of the copolymer. As the size and shape of particles remain unchanged during hydrolysis, a series of model suspensions with the same hydrodynamic properties (Newtonian or slightly pseudoplastic when no electric field was applied) but with different intensity of the electrorheological effect could be prepared. Under these conditions, the use of Mason number failed to correlate the apparent viscosity of suspensions of particles with different polarizability in the electric field. On the other hand, when polarizability of particles of a suspension system changes due to a higher temperature, a single curve in the plot of apparent viscosity vs. the Mason number could be obtained. Received: 17 February 1998 Accepted: 8 May 1998     

Photosensitive layers of TiO2/polythiophene composites prepared by electrodeposition

We adopted an electrophoretic deposition method for the preparation of thin layers of insoluble composite nanoparticles composed of TiO₂ core and about 2 nm thick shell of polythiophene, prepared by oxidative polymerization of thiophene. The reduced form of TiO₂-polythiophene composite material was deposited on the conductive surface from an ultrasonically generated microdispersion. Varying the dispersion media, applied voltage and the electrode arrangement made it possible to control the quality and morphology of the films. Compact semitransparent films deposited on ITO electrodes, suitable for photoelectrical measurements, were obtained within short deposition times.     

End-functionalized π-conjugated oligomeric materials for photoelectrical applications

Soluble poly(diphenylacetylene)s (PDA) capped with PhCO- groups (PDA-C) and Ph₂C= groups (PDA-P) were prepared via McMurry reductive coupling of benzil and carbonyl-olefin exchange reaction of tetraphenylethene and benzil, respectively. Fluoren-9-ylidene groups have been introduced into PDA by the McMurry coupling of PDA-C with fluoren-9-one and via copolymerization of benzil and fluoren-9-one. The oligomers prepared are stable in air, soluble in a variety of solvents. They can be processed by casting to form good-quality thin films suitable for measurements of electrical and optoelectrical properties.