Graft copolymerization of different mixtures of acrylic monomers on amylopectin. Swelling behavior

Hydroxylic and nonhydroxylic acrylates—methyl acrylate (MA), ethyl acrylate (EA), butylacrylate (BA), hydroxypropyl methacrylate (HPMA), ethylenglycol dimethacrylate (EGDMA), and mixtures of HPMA–MA, HPMA–EA, HPMA–BA in a 50/50 feed composition—were grafted onto amylopectin with different amounts of crosslinking agent, EGDMA. Percent of total conversion, percent crude grafting, and influence of pH in water content were studied. In this sense it was only at pH 10 when a real variation in the water content could be seen. It was also proved that the highest values were obtained when one of the comonomers was EGDMA with a 34 mol% of the initial feed composition. © 1994 John Wiley & Sons, Inc.     

Sphere Lower Bound for Rotated Lattice Constellations in Fading Channels

We study the error probability performance of rotated lattice constellations in frequency-flat Nakagami-m block-fading channels. In particular, we use the sphere lower bound on the underlying infinite lattice as a performance benchmark. We show that the sphere lower bound has full diversity. We observe that optimally rotated lattices with largest known minimum product distance perform very close to the lower bound, while the ensemble of random rotations is shown to lack diversity and perform far from it.     

Influence of deposition parameters on hole mobility in polymorphous silicon

Time-of-flight transient photoconductivity measurements reveal a monotonic increase with the deposition pressure in the hole mobility in polymorphous silicon for samples deposited under hydrogen dilution. With helium dilution, a maximum mobility that matches the highest value from H-dilution samples is measured at the intermediate pressure of 1.4 Torr. The deposition rate of those samples is twice the rate for the H-dilution ones. For the samples with the best hole mobilities, the valence-band tail is comparable to the one of standard hydrogenated amorphous silicon.     

Phase method for monitoring the permittivity of different media

A nondestructive method was developed for rapidly monitoring the permittivities of solid, liquid, and gaseous materials, based on measuring the phase difference of signals passing along two transmission lines and comparing the parameters of the “standard” and “investigated” media. The design of a volume-integral microwave transducer is considered together with its operating principle and its range of application. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 53–55, April, 1996.     

Subsecond thermophysics research at the Boris Kidrich Institute Vincha

In the early eighties, at the Boris Kidrich Institute Vincha, a method for measuring specific heat and electrical resistivity of electrical conductors in the millisecond resolution range was developed for measurements from room temperature to 1900 K. Over a period of nearly 10 years, the method was applied to different materials, including pure metals, ferrous, and nickel/ chromium alloys, and to the characterization of candidate materials for thermophysical property reference standards. This paper describes the method and reviews the results obtained in specific heat and electrical resistivity studies of ferromagnetic and other materials. The paper also demonstrates capabilities of the method for describing phase transitions or anomalies in pure metals (Fe, Co, Ni) or alloys (Nichrome, austenitic stainless steel).Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy.     

Application of substituted N-arylpyrroles in the corrosion protection of aluminium in hydrochloric acid

The inhibiting action of N-arylpyrroles on aluminium in 0.17 mol dm^–3 hydrochloric acid solution, in the temperature range 20–60 °C, was studied using potentiodynamic and electrochemical impedence spectroscopy techniques. The inhibiting efficiency of both investigated compounds 1-(2-fluorophenyl)-2,5-dimethylpyrrole (compound A) and 1-(2-fluorophenyl)-2,5-dimethylpyrrole-3-carbaldehyde (compound B) slightly increases with increasing temperature of the corrosive solution. Inhibitor adsorption on the elecrode surface decreases the apparent activation energy of the hydrogen evolution reaction. Compound A follows the Temkin adsorption isotherm, while its carbaldehyde derivative follows the Langmuir isotherm. The results of the apparent energy of activation and the standard free energy of adsorption point to stronger chemisorption of the compound A. However, due to additional condensation of molecules with carbaldehyde groups on the electrode surface, the carbaldehyde derivative exhibits even better inhibiting efficiency than compound A. The kinetic corrosion parameters, analysed in terms of the impedance data, show a satisfactory agreement with those obtained by the potentiodynamic method.     

On some interval methods for algebraic,exponential and trigonometric polynomials

New inclusion methods for the simultaneous determination of the zeros of algebraic, exponential and trigonometric polynomials are presented. These methods are realized in real interval arithmetic and do not use any derivatives. Using Weierstrass' correction some modified methods with the increased convergence rate are constructed. Convergence analysis and numerical example are included.     

Effect of Microstructure on the Accelerated Creep of 20CrMoV12‐1 and P 91 Steels

In the initial part the change of microstructure for steel X20 CrMoV 121 is discussed in terms of the distribution of carbide precipitates and its effects on accelerated creep resistance and hardness are presented. In the following, experimental results of microstructure and accelerated creep resistance are presented for the steels X20CrMoV 121 and P91 annealed for up to 8760 hours at 650°C and 750°C before the testing. A similar evolution of the distribution of carbide particles of a size above 102 nm is found for both steels, while the accelerated creep resistance is diminished much stronger for the steel X20CrMoV 121. This difference is due to a greater stability of NbC than that of VC precipitates, both related to the evolution of the chemical composition of complex chromium, molybdenum and iron carbide particles.