We show that an in situ Kerr rotation measurement is a very effective technique for the study of antiferromagnetic (AF) ferromagnetic (F) film couples. Magnetic signals can be obtained even in the case where the (AF) is the top layer up to at least 200 A of AF thickness. We have used this in situ approach combined with ion milling to study the thickness dependence of the magnetic properties of MnsoFesoiNisoFe2o systems. We observe that the exchange bias field has a surprisingly sharp onset at a critical thickness of AF -50 A. We show that this is consistent with a simple model and that the magnetic anisotropy of MnFe can be estimated from the observed critical thickness to be -1.35 X 105 erg/cm3. The exchange field showed the predicted proportionality to the inverse of the F thickness from -50 to 400 A. Auger spectroscopy and spin polarized secondary electron emission have been used to rule out gross artifacts due to ion milling.

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In this paper, an analysis of knock signals suggests that the knock intensity is a cyclically uncorrelated random process, and that it is therefore not possible to control individual cycles to a specified knock intensity in a deterministic manner. A new knock control algorithm is therefore developed on the basis of a stochastic interpretation of the knock signal, and on the basis of a control objective specified as a certain percentage of knocking cycles. Unlike traditional controllers, the new algorithm does not respond to knock events provided that these are occurring within a specified tolerance of the target knock rate. The new controller uses the cumulative summation of knock events to make this determination, thereby avoiding the slow transient response times sometimes associated with ‘stochastic’ knock controllers. When a spark adjustment is deemed necessary, the magnitude of the control action is scaled according to the likelihood ratio of the observed events since the last spark adjustment was made. A theoretical analysis of the new controller is presented and a simulation tool which is closely based on experimental data is used to assess its performance. The results show that the new controller is able to achieve the same target knock rate as a traditional controller while operating at a more advanced mean spark angle. There is also less cyclic variance about this mean and the regulatory response is significantly improved. The transient response to overly advanced or retarded conditions is similar to the traditional controller. These results suggest that the new controller will deliver increased torque and engine efficiency under knock-limited conditions without increasing the risk of engine damage.

In recent years, surface analytical methods that determine structure have been combined with methods that measure elemental composition and oxidation states, to yield an improved understanding of lubricant‐derived tribofilms. Methods assessing the mechanical properties of thin films have also been applied to tribofilms with thicknesses of the order of nanometres. These methods, in combination with chemical and physical studies of bulk lubricant systems and assessments of lubricant behaviour in tribological environments, have made it possible to describe comprehensively film forming mechanisms, structures and tribological properties. This paper outlines the initial results of such an attempt, focusing on zinc dialkyl dithiophosphates and overbased detergents in model systems and engine oils.

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