Complex permeability of soft magnetic ferrite polyester resin composites at frequencies above 1 MHz

Composite soft magnetic materials consist of magnetic particles in a non-magnetic matrix. The properties of such materials can be modelled using effective medium theory. Measurements have been made of the complex permeability of composites produced using ferrite powder and polyester resin. The success of various effective medium expressions in predicting the variation of complex permeability with composition has been assessed

Correaltion of full-scale drag predictions with flight measurements on the C-141A aircraft. Phase 2: Wind tunnel test, analysis, and prediction techniques. Volume 1: Drag predictions, wind tunnel data analysis and correlation

The degree of cruise drag correlation on the C-141A aircraft is determined between predictions based on wind tunnel test data, and flight test results. An analysis of wind tunnel tests on a 0.0275 scale model at Reynolds number up to 3.05 x 1 million/MAC is reported. Model support interference corrections are evaluated through a series of tests, and fully corrected model data are analyzed to provide details on model component interference factors. It is shown that predicted minimum profile drag for the complete configuration agrees within 0.75% of flight test data, using a wind tunnel extrapolation method based on flat plate skin friction and component shape factors. An alternative method of extrapolation, based on computed profile drag from a subsonic viscous theory, results in a prediction four percent lower than flight test data

Comparison of Microanalysis Using Energy-Dispersive X-Ray Spectroscopy and Electron Energy Loss Spectroscopy

The work presented in this thesis is concerned with the development and comparison of two techniques for microanalysis in the electron microscope. These are energy-dispersive x-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS). Particular emphasis has been placed on light element analysis, as these elements have become accessible to EDX analysis with the recent advent of windowless x-ray detectors. The interest here is confined to analysis without recourse to standard specimens of known composition. Standardless analysis requires a theoretical knowedge of the processes which give rise to the various features in both types of spectrum. Chapter 2 outlines the formalism of the relevant basic theory, and describes how expressions are obtained for the cross sections relevant to inelastic scattering of electrons by interactions with inner-shell electrons in the specimen, and to the x-ray production which is associated with such scattering. The signals in EELS and EDX spectra which arise due to inner shell scattering occur at energy losses and photon energies respectively which are characteristic of the atoms in the specimen. Other processes, which contribute to non-characteristic backgrounds in both cases, are described briefly. The work for this thesis was carried out using three microscopes: two similar scanning transmission electron microscopes (STEMs), one of which was equipped with a windowless x-ray detector, and one transmission electron microscope (TEN). Chapter 3 gives a description of one of the STEMs, and goes on to outline the differences between the two STEMs. The TEM is then briefly described. The remainder of the chapter discusses the detectors and spectral acquisition systems fitted to each microscope. The results obtained on EDX are presented in chapters 4, 5 and 6. Chapter 4 starts by discussing general EDX analysis techniques, and then goes on to detail a series on measurements of the ratios of characteristic signals to the local background in the EDX spectrum. The results obtained using all three microscopes are then used as the basis of a parameterisation of the ionisation cross section for the K-shell. The parameterisation allows the prediction of this quantity within an accuracy of ~20% over a range of elements with 14 and a range of accelerating voltages from 80keV to 200k. eV. Chapter 5 details the investigation of L-shell ionisation cross sections. This involved measuring the ratio of the K-shell/L-shell cross sections over a wide range of elements, and using the results of the previous chapter to deduce the L-shell cross sections. These measurements required the detector efficiency to be carefully considered over the entire energy range of an EDX spectrum. The accuracy with which the L-shell cross sections could be determined was limited by uncertainties in the values in the literature for the relevant fluorescence yields. Nevertheless, the results generally suggested that the model used for the K-shell may be applied also to the L-shell. Chapter 6 gives the results of the analyses of a number of compounds of light elements, and shows that many difficulties exist in the determination of quantitative information on these elemnts by EDX. EELS analysis procedures are discussed in chapter 7. Conventional procedures, and an alternative technique proposed by Steele et al. (1985), are detailed. The latter approach involves the inclusion in the function which is fitted to the spectrum of a scaled theoretical cross section. Fitting may then be carried out both before and after the characteristic edge onset. This removes the need for the background to be extrapolated beneath the edge, as conventional background fitting requires. Results of the application of the new procedure are given in chapter 8. Firstly, it is used to re-analyse EELS data which had previously been analysed conventionally. These data were recorded simultaneously with equivalent EDX data. The results showed that the use of the new technique leads to some improvement in the correlation between concentration ratios determined using EELS and EDX. A second analysis, of TiB2 end CrB2 failed to produce any conclusive results. Finally, chapter 9 discusses the implications of the results obtained in this work, and suggests some ways in which the accuracy of each of the two techniques might be improved

U-Pn geochronology of deformed metagranites in central Sutherland, Scotland: evidence for widespread late Silurian metamorphism and ductile deformation of the Moine Supergroup during the Caledonian orogeny

Within the Caledonides of central Sutherland, Scotland, the Neoproterozoic metasedimentary rocks of the Moine Supergroup record NW-directed D2 ductile thrusting and nappe assembly, accompanied by widespread tight-to-isoclinal folding and amphibolite-facies metamorphism. A series of metagranite sheets which were emplaced and penetratively deformed during D2 have been dated using SHRIMP UâPb geochronology. Zircon ages of 424 8 Ma (Vagastie Bridge granite), 420 6 Ma (Klibreck granite) and 429 11 Ma (Strathnaver granite) are interpreted to date emplacement, and hence regional D2 deformation, during mid- to late Silurian time. Titanite ages of 413 3 Ma (Vagastie Bridge granite) and 416 3 Ma (Klibreck granite) are thought to date post-metamorphic cooling through a blocking temperature of c. 550â 500 8C. A mid- to late Silurian age for D2 deformation supports published models that have viewed the internal ductile thrusts of this part of the orogen as part of the same kinematically linked system of forelandpropagating thrusts as the marginal Moine Thrust Zone. The new data contrast with previous interpretations that have viewed the dominant structures and metamorphic assemblages within the Moine Supergroup as having formed during the early to mid-Ordovician Grampian arcâcontinent orogeny. The mid-to late Silurian D2 nappe stacking event in Sutherland is probably a result of the collision of Baltica with the Scottish segment of Laurentia

Suprathermal plasma observed on STS-3 Mission by plasma diagnostics package

Artificially produced electron beams were used extensively during the past decade as a means of probing the magnetosphere, and more recently as a means of actively controlling spacecraft potential. Experimentation in these areas has proven valuable, yet at times confusing, due to the interaction of the electron beam with the ambient plasma. The OSS-1/STS-3 Mission in March 1982 provided a unique opportunity to study beam-plasma interactions at an altitude of 240 km. On board for this mission was a Fast Pulse Electron Generator (FPEG). Measurements made by the Plasma Diagnostics Package (PDP) while extended on the Orbiter RMS show modifications of the ion and electron energy distributions during electron beam injection. Observations made by charged particle detectors are discussed and related to measurements of Orbiter potential. Several of the PDP instruments, the joint PDP/FPEG experiment, and observations made during electron beam injection are described