Generic impulse response function for MOS systems and itsapplication to linear response analysis

A generalized response function is presented that can describe several of the practically important transient-response features of MOS systems. It allows for deviations from strict logarithmic time dependencies yet is mathematically tractable in performing linear response analysis. Fits of the generic response function to experimental data are discussed, including the short-term recovery due to hole transport, the long-term recovery due to trapped hole annealing, and the long-term, time-dependent buildup of interface traps. Analytic results for the convolution integral of linear response theory are derived for a square irradiation pulse, and some simple applications are discussed     

Effect of thermal residual stresses on fatigue crack opening and propagation behavior in an Al/SiC p metal matrix composite

The effects of a thermal residual stress field on fatigue crack growth in a silicon carbide particle-reinforced aluminum alloy have been measured. Stress fields were introduced into plates of material by means of a quench from a solution heat-treatment temperature. Measurements using neutron diffraction have shown that this introduces an approximately parabolic stress field into the plates, varying from compressive at the surfaces to tensile in the center. Long fatigue cracks were grown in specimens cut from as-quenched plates and in specimens which were given a stress-relieving overaging heat treatment prior to testing. Crack closure levels for these cracks were determined as a function of the position of the crack tip in the residual stress field, and these are shown to differ between as-quenched and stress-relieved samples. By monitoring the compliance of the specimens during fatigue cycling, the degree to which the residual stresses close the crack has been evaluated. formerly Research Student, Department of Materials Science and Metallurgy, University of Cambridge formerly Lecturer, Department of Materials Science and Metallurgy, University of Cambridge This article is based on a presentation made in the symposium entitled “Creep and Fatigue in Metal Matrix Composites” at the 1994 TMS/ASM Spring meeting, held February 28–March 3, 1994, in San Francisco, California, under the auspices of the Joint TMS-SMD/ASM-MSD Composite Materials Committee.     

PALAEOZOIC TECTONIC HISTORY OF SE TURKEY

A review of published data for the Palaeozoic of SE Turkey, together with facies distribution and palaeo-fault maps derived from regional field data, are used to interpret the Palaeozoic tectonic history of the region.
Intracratonic rifting events in the Early Cambrian and the Early Ordovician led to syn-rift deposition within fault-bounded basins. Marine transgressions across the region in the mid-Cambrian and mid-to-Late Ordovician were probably influenced by regional thermal subsidence after each rifting event, in addition to (glacio-)eustatic mechanisms. Marine transgressions in the Early Silurian and Early Carboniferous are thought to have been entirely eustatic in origin.
Poorly-constrained, Late Palaeozoic facies variations across the region can be related to uplift during the Caledonian and Hercynian orogenic episodes. Widespread tilting and erosion before the Cretaceous, which has removed much of the Late Palaeozoic record from this region, resulted from uplift at the edges of a major rift system which was initiated during the Triassic-to-Jurassic opening of the Southern Neotethys.     

Book review

CLIMATIC FLUCTUATIONS AND WATER MANAGEMENT. by M. A. Abu‐Zeid and A. K. Biswas Butterworth Heinemann, Oxford, 1992, 356 pp, £50.00.     

Composition for the protection of aluminum alloys against exfoliation corrosion

Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 10, pp. 21–22, October, 1992.     

Nuclear Magnetic Resonance Studies of Silicon Carbide Polytypes

The ²⁹Si MAS NMR spectra of the 2H, 4H, 6H, and 3C polytypes of silicon carbide are presented. An attempt is made to correlate differences in the chemical shifts with local atomic environment. The results of the analysis of the spectra of pure polytypes are used as a basic for the interpretation of the spectra of mixed polytypes and a discussion of the crystallinity and impurity levels of different samples. Carbon-13 chemical shifts obtained from spectra of the same polytypes are also tabulated.