Statistical analysis of bend strength data according to different evaluation methods

The strength values obtained in four series of bend tests on two monolithic ceramic materials have been statistically evaluated. Statistical mapping procedures were used to check whether a Weibull distribution fits the strength data. Where this has been found to be the case, the value of the Weibull parameters determined according to different evaluation methods fall within each other's confidence interval. The values of the modulus m and of the characteristic strength σ₀ of the two-parameter distribution can differ significantly from the corresponding values in the three-parameter distribution.     

Synthesis and characterization of poly(siloxane-urethane)s

A series of polyurethane block copolymers based on hydroxy-terminated polydimethylsiloxane and poly(propylene glycol) soft segments of molecular weights 1818 and 2000, respectively, were synthesized. The hard segments consisted of 4,4′-diphenylnethane diisocyanate and 1,4-butanediol as the chain extender. Samples with different molar ratios were prepared. We tried to synthesize polydimethylsiloxane-based polyurethanes (PDMS-PU) containing a hard block as major fraction and a soft block as minor fraction for preparing toughened rigid systems. After a study of the pure polydimethylsiloxane-based polyurethane and poly(propylene glycol)-based polyurethane (PPG-PU), (mixed polyol)-based block copolymers and blends of PDMS-PU and PPG-PU were synthesized, and characterized by means of differential scanning calorimetry, tensile testing and scanning electron microscopy. In (mixed polyol)-based copolymers and lower hard-segment content blends, macro-phase separation occurred, but blends with higher hard-segment contents showed significant reduction in amounts of phase separation.     

Micellar polymerisation of ionic surfactants studied by conductimetry

The micellar polymerisation of ionic surfactants such as allyldodecyl-dimethylammonium bromide and 3-dodecyl-1-vinyl imidazolium iodide has been studied by conductimetry in aqueous solution. The polymerisation was carried out using two different sources of γ rays directed into solutions of surfactant above the critical micellar concentration. Conductimetry is shown to be a very good physicochemical method for analysis of these solutions. The results showed different behaviour for the two surfactants, which has highlighted a change in the structure of their aggregates which led to the assumption of an interaction between the polymers of high mass and different products of the polymerisation (oligomers, products of degradation, monomers etc.). Ultrafiltration experiments coupled with ¹H-NMR and conductivity analysis confirm these assumptions.     

HYDROCARBON POTENTIAL OF NORTHERN IRELAND: Part III. Reservoir potential of the Permo-Triassic

Thick Permo-Triassic sandstones occur in two basins in Northern Ireland. The sandstones are fluvio-deltaic, including an oolitic facies, and are interbedded with mudrocks. They exhibit petrographic features which are typical of red beds and are widely found in the Permo-Triassic elsewhere in the British Isles. The predominant cements are haematite, potassium feldspar. illite and carbonates. Gypsum, anhydrite and dolomite cements occur in the regions of deepest burial. which represent the basin centres. There was widespread leaching of carbonate/sulphate cements, but calcite is preserved in the oolitic facies and below the sub-Cretaceous (chalk) unconformity. The dissolution of cements and framework grains was due to leaching by meteoric fluids. Precipitation of kaolinite in secondary pores, and subsequent illitization, represent fluctuations in the meteoric hydraulic head. Deep boreholes exhibit sandstone porosities which indicate that there may be significant reservoir potential where adequate seals and traps are present.     

COMMENTS ON "GRAVITY OVERTURNS, EXTENSION, AND BASEMENT FAULT ACTIVATION"

Koyi (1991) has described physical modelling experiments on the initiation of salt diapirism. He also compares his results with the results of an investigation of salt tectonics in the northern part of the Norwegian-Danish Basin by Hospers et al. (1988).
Koyi's comments on this investigation are not altogether favourable. Below, I intend to show that Koyi's criticisms are not valid, as they stem from a combination of: (1) built-in features present in his models which limit their applicability; and (2) an incomplete understanding of the structural setting in which salt diapirism was initiated in the northern part of the Norwegian-Danish Basin.     

Lubricant formulations with improved bioresistance

Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 8, pp. 29–30, August, 1992.     

Updating a steel mill power system to improve reliability anddecrease energy costs

The cost of electricity and operating reliability in heavy industry can be key in determining which processes and plants survive in today's competitive market. This paper provides an insight into the planning and implementation of several significant cost saving and reliability improvements at a turn-of-the-century steel mill in Ohio. A clear understanding of what to look for and how to proceed with such projects should provide motivation for others considering similar improvements