SUMMARYA novel method is proposed for the numerical computation of Fourier coefficients in the range of higher frequencies for which hitherto no practical method was available. The accuracy of the results obtained by application of this method is discussed, and bounds of a correction term are determined accordingly. An example from the field of Diesel engine research is given, and the computed spectrum is compared with the spectrum recorded by an electronic harmonic analyzer.

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The well-known logarithmic friction factor diagram for laminar pipe flow can be extended in the following two respects: For application to non-Newtonian fluids, by incorporating in the plot a modified form of the consistency curve for a given material. Methods are discussed of obtaining these curves, and of transforming them into the required shape. For prediction of flow resistance through valves and fittings, by use of an auxiliary diagram based on results of appropriate tests. The general procedure is outlined, and it is stressed that results cannot be relied on quantitatively, until test data are obtained for wider ranges of sizes and types than hitherto available.

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ConclusionWith the exception of the 50 kV radiation quality, for which the NBS correction (K,)B is inadequate, the results indicate that direct comparison measurements with two free-air chambers, even with quite different geometries (BIPM/NBS), can be made in the lowenergy X-ray region with a discrepancy Of less than 0.3%. This is in accoIdance with the expected uncertainty. An effort should be made to decrease uncertainties due to electric field distortion, which makes much the largest contribution to the uncer-A. ALLISY (BIPM). They wish also to thank A. BROSED (JEN, Spain) who, during his stay at the BIPM, made a valuable contribution to the work involved in the comparison. M.