Semi-Automated Polarography with a Modified Technicon Sampler

ABSTRACT

A electrode holder, with polarographic electrodes and four deoxygenation probes, was mounted on the mixing assembly bracket of a Technicon Sampler II. The assembly lowers the electrodes into the cuvette in the position normally sampled and the deoxygenation probes into the preceeding cuvettes. Air is excluded through a modification of standard cover plates. A constant potential is applied across the electrodes and the resultant current recorded continuously while the samples change. The system was evaluated through the assay of a pharmaceutical containing nitroglycerin. Operating at rates between 30 and 70 samples per hour, the system has a precision of about 1%.     

Activated basket anodes from nickel powder Part II: Fabrication of anodes by a liquid phase sintering process

A process has been developed for the fabrication of sulphur activated basket anodes from nickel powder for use in the electroplating industry. These anodes have satisfactorily high anode current efficiency, lead to high cathode current efficiency, give good quality electroplate and yield anode residues of 0.5% or less.     

Activated basket anodes from nickel powder Part I: Laboratory facilities for assessing the performance of anodes in nickel electroplating baths

Laboratory-scale facilities have been developed for evaluating the potential performance of nickel basket anodes in an industrial electroplating circuit. Two types of electroplating baths were investigated-one for testing single anodes and the other for testing multiple anodes in small baskets under simulated industrial conditions. By the use of reference nickel anodes whose industrial performance was already known, it was established that both facilities provided an economical means of determining the electrochemical activity and current efficiencies of experimental anodes being developed for industrial use. Importantly, they also provided the means of establishing the amount of residue likely to be generated by such anodes in an industrial situation.     

Quantitative Analysis of High-Alumina Refractories Using X-ray Powder Diffraction Data and the Rietveld Method

Quantitative determination of phase abundance in high-alumina refractories has been performed using the Rietveld refinement method applied to X-ray powder diffraction data. The use of a "whole-pattern" method for analysis has allowed the simultaneous determination of accurate unitcell parameters and the phase abundance of major (mullite and cristobalite) and minor (quartz, corundum, and andalusite) phases. A comparison of the accurate unit-cell parameters, produced during refinement, with published data has allowed the composition of mullite to be estimated at 3:2 Al₂O₃:SiO₂. Cristobalite has been shown to be present in two distinct forms, both of which have been quantified in spite of severe overlap in their diffraction patterns. There is excellent agreement between SiO₂ and Al₂O₃ contents calculated from the measured phase contents and those measured by X-ray fluorescence spectrometry. The addition of fluorite in a known amount as an internal standard has allowed the estimation of the amount of amorphous material present.     

Parallel genetic simulated annealing: a massively parallel SIMDalgorithm

Many significant engineering and scientific problems involve optimization of some criteria over a combinatorial configuration space. The two methods most often used to solve these problems effectively-simulated annealing (SA) and genetic algorithms (GA)-do not easily lend themselves to massive parallel implementations. Simulated annealing is a naturally serial algorithm, while GA involves a selection process that requires global coordination. This paper introduces a new hybrid algorithm that inherits those aspects of GA that lend themselves to parallelization, and avoids serial bottle-necks of GA approaches by incorporating elements of SA to provide a completely parallel, easily scalable hybrid GA/SA method. This new method, called Genetic Simulated Annealing, does not require parallelization of any problem specific portions of a serial implementation-existing serial implementations can be incorporated as is. Results of a study on two difficult combinatorial optimization problems, a 100 city traveling salesperson problem and a 24 word, 12 bit error correcting code design problem, performed on a 16 K PE MasPar MP-1, indicate advantages over previous parallel GA and SA approaches. One of the key results is that the performance of the algorithm scales up linearly with the increase of processing elements, a feature not demonstrated by any previous parallel GA or SA approaches, which enables the new algorithm to utilize massive parallel architecture with maximum effectiveness. Additionally, the algorithm does not require careful choice of control parameters, a significant advantage over SA and GA     

A Study of Explanation-Based Methods for Inductive Learning

This paper formalizes a new learning-from-examples problem: identifying a correct concept definition from positive examples such that the concept is some specialization of a target concept defined by a domain theory. It describes an empirical study that evaluates three methods for solving this problem: explanation-based generalization (EBG), multiple example explanation-based generalization (mEBG), and a new method, induction over explanations (IOE). The study demonstrates that the two existing methods (EBG and mEBG) exhibit two shortcomings: (a) they rarely identify the correct definition, and (b) they are brittle in that their success depends greatly on the choice of encoding of the domain theory rules. The study demonstrates that the new method, IOE, does not exhibit these shortcomings. This method applies the domain theory to construct explanations from multiple training examples as in mEBG, but forms the concept definition by employing a similarity-based generalization policy over the explanations. IOE has the advantage that an explicit domain theory can be exploited to aid the learning process, the dependence on the initial encoding of the domain theory is significantly reduced, and the correct concepts can be learned from few examples. The study evaluates the methods in the context of an implemented system, called Wyl2, which learns a variety of concepts in chess including skewer and knight-fork.     

Activated basket anodes from nickel powder Part III: Electrochemical behaviour of sulphur activated anodes

The characteristics of anodic dissolution of nickel electroplating anodes produced from compacted nickel powder by a liquid phase sintering process have been determined. Sulphur incorporated in the sintered product was found to increase the electrodissolution activity and inhibit passivation. The activity of the anodes increased with increase in sulphur content and approached that of commerical sulphur-depolarized anodes produced by electroforming. Sintering temperature and rate of cooling during preparation of the anodes had little influence on the dissolution activity and resistance to passivation. No direct relationship was found between activity and the generation of anode fines. The rate of anodic dissolution of sulphur-containing anodes has been found to be comparable to that for synthetic heazlewoodite (Ni₃S₂ electrodes). The influence of the presence of sulphur on the kinetics of nickel dissolution is interpreted in terms of the development on the metal surface of Ni₃S₂ from which nickel is extracted to leave a sulphide of lower nickel content; the latter sulphide then reacts with underlying elemental nickel to reform Ni₃S₂.