The Measurement of Silicon, Tin, and Titanium in Jet-Engine Oil
A wear metal profile is often prepared for each engine. Typically an early wear-in period of high metals concentration is observed, followed by a plateau of low metals concentration [2]. Impending component failure will be indicated by a rapid increase in wear metal concentration, or the sudden appearance of a metal. The metal type and concentration may also indicate to the analyst and engineers which part of an engine is failing. A change in the concentration of sodium for example, may indicate an antifreeze leakage, the increased presence of lead may indicate the wear of bearings in a diesel engine [3].
Spectrometric oil analysis. Detecting engine failures before they occur
The spectrometric analysis of wear metals in engine oils is reviewed. It is shown that the standard techniques used by the United States Air Force - rotating-disk electrode atomic emission spectrometry (RDE-AES) and flame atomic absorption spectrophotometry (AAS) - suffer from errors introduced by interelement and matrix interferences and most notably by the particle size of the wear metal. Considerable effort has been expended to develop a particle size independent analytical spectroscopic technique. The dissolution of the oil sample in an acid prior to spectrochemical analysis promises more uniform results of wear metal content. It is noted that great care must be exercised in sampling and in retaining the integrity of the sample over the course of the analysis. 24 references, 4 figures, 2 tables.
The Earth's Angular Momentum Budget on Subseasonal Time Scales
Irregular length of day (LOD) fluctuations on time scales of less than a few years are largely produced by atmospheric torques on the underlying planet. Significant coherence is found between the respective time series of LOD and atmospheric angular momentum (AAM) determinations at periods down to 8 days, with lack of coherence at shorter periods caused by the declining signal-to-measurement noise ratios of both data types. Refinements to the currently accepted model of tidal Earth rotation variations are required, incorporating in particular the nonequilibrium effect of the oceans. The remaining discrepancies between LOD and AAM in the 100- to 10-day period range may be due to either a common error in the AAM data sets from different meteorological centers, or another component of the angular momentum budget.