The hydrogen content at O"C, 1 atm, is n = 0.73 [Ill; the ratio of the diffusion coefficients can be obtained from the measurements in Fig. 3 as: DDO,/D, = 0.85. Equation (4a) then yields: pD = 0.15.The order of magnitude: about 10% of the diffusion jumps in P-phase PdD, are displacement jumps, seems not unreasonable.In the second case, tracer diffusion of tritium in PdH,, we get instead of Equation (4):The ratios of the probabilities p can be related to the difference of the activation energies EH -E, = d E and to the ratio of the frequency factors w i and w: in the same way as before.But now, contrary to the case before, A E < 0 and wi/w: < 1.Since values from the pure P-phase PdT, are not available we will, for purpose of estimation, make use of the a-phase values ConclusionThe numerical values obtained here can not be taken for more than first approximations. For a better base of numerical data the experimental techniques and the precision of their results have to be improved markedly. The foregoing considerations may have shown that it would be worth while to develop such improvements. They would open a new approach to investigating correlation problems which could hardly be studied in so clear and distinct way with other diffusion systems of more complicated nature. AcknowledgementWe gratefully acknowledge the financial support of the experimental investigations by the Deutsche Forschungsgemeinschaft providing for stipends and for equipment. The diffusion of dissolved hydrogen in two metals welded together and with different affinities to hydrogen is investigated experimentally and theoretically. The hydrogen distribution is measured nondestructively by a collimated Cadmium-filtered neutron beam of the FRG-1. For theoretical analysis the methods of expanding the solution into eigenfunctions of the problem must be generalized towards piecewise continuous eigenfunctions because of the concentration jump at the boundary between the two metals. The diffusion constants and the Nernst distribution coefficient are determined by a special method from the experimental curves. ReferencesDie Diffusion von gelostem Wasserstoff in zwei aneinandergeschweiBten Metallen mit unterschiedlicher Affinitat gegenuber Wasserstoff wird experimentell und theoretisch untersucht. Mit Hilfe eines mit Cadmium gefilterten Neutronenstrahls des FRG-1 werden die Konzentrationskurven des Wasserstoffs zerstorungsfrei gemessen. Eine Verallgemeinerung der Eigenfunktionsmethode auf stuckweise stetige Eigenfunktion erkdubt die geschlossene Losung bei Berucksichtigung des Konzentrationssprungs an der Grenze zwischen beiden Metallen, der nach dem Nernstschen Verteilungssatz auftritt. Nach einem speziellen Verfahren werden die Diffusionskonstanten und der Nernstsche Verteilungskoeffizient aus den gemessenen K u m n bestimmt.operation, because the consequent precipitation of zirconium hydride in the metal is detrimental to the mechanical behaviour of the fuel cans. On account of its technical importance much work has been devoted to the solubility...

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Die Diffusion von gelöstem Wasserstoff in zwei aneinandergeschweißten Metallen mit unterschiedlicher Affinität gegenüber Wasserstoff wird experimentell und theoretisch untersucht.

The paper provides an empirical analysis of the macroeconomic factors that enhance revenue gap in South Africa using the multivariate cointegration techniques for the period 1965 to 2012. The results from the cointegration analysis indicate that the revenue gap in South Africa is negatively associated with the level of imports while positively related to external debt and underground economy. The former finding is consistent with the notion that imports are subjected to more taxation than domestic activities because of certain features of international trade that tend to make tax evasion difficult. On the other hand, the positive relationship between external debt and tax gap shows that the South African government relies upon external debt to finance its budget deficit resulting from missing revenues. Furthermore, the observed negative effect of the post-apartheid dummy confirms that the tax policy reforms that South Africa introduced following the liberation in 1994 have led to a reduction in missing revenues. The results from the Granger causality test also show that there is a unidirectional causality running from imports and underground economy to revenue gap, while revenue gap on the other hand is found to Granger-cause national income and external debt in South Africa.

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