The Effects of Aging Precipitation on the Recrystallization of CuNiSiCr Alloy

The interaction between precipitation and recrystallization and its effect on the properties of the Cu-Ni-Si-Cr alloy during aging were discussed. The results show that the deformation results in much more dispersed precipitation of the phases. The precipitations have accelerating or retarding effects on the recrys allization. On the formation and growth of recrystallization, the precipitated phases are coarsed or dissolved in front of grain boundaries following a re-precipitation in the recrystallization area.     

Comparison between cellular automata and linear feedback shift registers based pseudo-random number generators

A detailed comparison between pseudo-random number generators (PRNGs) based on cellular automata (CA) and linear feedback shift registers (LFSRs) is presented in this paper. Various statistical tests have been applied in order to reveal the advantages and disadvantages of both approaches. Both LFSRs and hybrid additive cellular automata (HACA) produce satisfactory PRNGs. HACA operate at higher speeds than LFSRs with the same characteristic polynomials. Regarding the silicon area, direct comparisons between the two approaches cannot be made since it depends on the PRNG length. However, the inherent modularity of HACA reduces the silicon area occupied by them and, when long feedback paths are used, the silicon area occupied by LFSRs increases.     

Signed Systems for Paraconsistent Reasoning

We present a novel approach to paraconsistent reasoning, that is, to reasoning from inconsistent information. The basic idea is the following. We transform an inconsistent theory into a consistent one by renaming all literals occurring in the theory. Then, we restore some of the original contents of the theory by introducing progressively formal equivalences linking the original literals to their renamings. This is done as long as consistency is preserved. The restoration of the original contents of the theory is done by appeal to default logic. The overall approach provides us with a family of paraconsistent consequence relations.Our approach is semantical because it works at the level of the propositions; it deals with the semantical link between a proposition and its negation. The approach is therefore independent of the combination of the connectives that are actually applied to the propositions in order to form entire formulas.     

Quantitative x-ray microanalysis of spherical inclusions embedded in a matrix using a SEM and Monte Carlo simulations

The current schemes of quantification of x-ray microanalysis in the SEM [ZAF and σ(ρZ) methods] are valid for specimens of homogeneous composition. The determination of the chemical composition of small inclusions using these techniques is impossible because the volume of x-ray emission is not of homogeneous composition. A scheme of quantification to determine the composition of small inclusions embedded in a matrix has been developed using Monte Carlo simulations. This scheme is similar to that developed by Kyser and Murata (1974) for the quantification of thin foils deposited on a substrate using x-ray microanalysis in the SEM.     

A simple but realistic model for laser cladding

A model which takes into account the main phenomena occurring during the laser-cladding process is proposed. For a given laser power, beam radius, powder jet geometry, and clad height, this model evaluates two other processing parameters, namely, the laser-beam velocity and the powder feed rate. It considers the interactions between the powder particles, the laser beam, and the molten pool. The laser power reaching the surface of the workpiece is estimated and, assuming this power is used to remelt the substrate with the clad having been predeposited, the melt-pool shape is computed using a three-dimensional (3-D) analytical model, which produces mmediate results, even on personal computers. The predictions obtained with this numerical model are in good agreement with experimental results. Processing engineers may therefore use this model to choose the correct processing parameters and to establish cladding maps. Formerly Postdoctoral Fellow, Physical Metallurgy Laboratory.     

Structure of oxide gels and glasses by infrared and Raman scattering

Optically clear monolithic gels and fine gel powders have been synthesized using various alkoxide hydrolysis reactions. The gels have been characterized using various methods to determine their structures. (X-ray diffraction, DTA, TGA, DSC, IR and Raman spectroscopies). The spectra and the nature of gels depend on the solvent and the hydrolysis conditions (rate, pH, etc.). The use of acetone as solvent allows reduction of the hydrolysis time, from weeks to hours. If the hydrolysis of aluminium sec-butoxide is too rapid, at high pH, crystalline bayerite Al(OH)₃ is formed. Regular hydrolysis leads to amorphous optically clear gel with sometimes boehmite (or diaspore) traces. Formation of the (porous) glass (300 to 600°C) and also of the γ-alumina does not modify the Raman spectra strongly whereas large modifications are observed on IR spectra with the evolution of protonic species. The structure of alumina gel and glass is of the spinel type. The α-alumina phase grows above 1200 to 1250°C (above 1050°C if boehmite traces are present).     

NOTE ON A METHOD FOR THE CALCULATION OF TRUE EXTRACT WITH ALLOWANCE FOR GRAINS VOLUME

The extract of a malt determined by the Standard Method is seriously in error because of the incorrect allowance of 15 ml. as the volume of the grains. However, the results can be accurately corrected by a simple calculation, or by reference to a table.     

VITAMIN B1 AND RIBOFLAVIN IN BREWING

Vitamin B₁ has been determined in a large number of beers by the fermentation method of Schultz, Atkin and Frey which has not previously been applied to worts and beers. In general, the highest amounts were found in beers of high original gravity and in those made almost entirely from malt. Well-attenuated and unprimed beers give the highest ratio, units of B1: calories. During the brew the malt, almost the sole source of vitamin B₁, yields up the vitamin to the wort, which in its turn loses most of it to the yeast. Most of the vitamin B₁ results have been confirmed by the thiochrome method involving an entirely different principle, whilst the general validity of both methods was further confirmed by animal feedings tests. Determination of Riboflavin (vitamin B₂) by the microbiological method of Snell and Strong has led to the following conclusions:—Riboflavin is formed during germination of barley and in growing yeast. Most of the riboflavin of the malt passes into the wort during mashing and sparging and remains in the beer, the yeast not taking out any appreciable quantity. The number of microgrms. of riboflavin per 100 ml. of beer, in general, exceeds somewhat the number of degrees of original gravity.