Table of contents

A model for an absorbing molecule immersed in a damping medium is discussed in terms of linear response. This model is closely related to the itinerant oscillator model used to describe orientational absorption in fluids, and the natural expression for its response corresponds closely to an approximant of a general expansion due to Mori (1965). The model is applied to the far infrared absorption of stannic iodide dissolved in cyclohexane.

In ferroelectrics the domain structure in thin crystals is mostly determined by the surface impurities. In thick crystals of KNbO₃ with thickness greater than about 0.04 cm, however, domains are known to be formed through volume nucleation, and dislocations to play some role. The role of impurities must also be expected to be significant, especially when the elastic energy considerations are predominant in determining the domain configurations. On successive etching of thin flakes of thickness of about 0.02 cm obtained from the thick crystals of KNbO₃ by dilute HNO₃ a stage is found when a domain wall shows a series of black dots on it. Different walls show these dots at different stages of etching, and a wall may be 60 degrees as well as 90 degrees . Almost all the walls show this behaviour at one stage or the other indicating its general nature, and reasons are given to suggest that the dots may represent the impurity sites in the bulk. The etchant is also found to attack the regions near the domain wall selectively.

The use of Auger electron spectroscopy to monitor the oxidation of GaP(110) is discussed. Although the electron beam is turned off during exposure and for some time afterwards, a strong dependence is found of the oxygen Auger peak height on the elapsed time since the electron beam was switched on again. A mechanism for this is proposed, involving absorption of oxygen on to the filament of the electron gun and the ceramic supports of the filament. The gradual diffusion of oxygen into the electron beam followed by ionization and projection towards the sample is then possible. It is suggested that, in such experiments, the filament should be heated, with the beam deflected away from the sample, for several hours before reliable results can be obtained.

Recent mathematical results are used to give an exact treatment of the problem of frequency modulation as achieved by varying C or L (capacitance or inductance). Stability regions are found for arbitrary fractional deviation of the frequency. In various limits the exact results of the theory are supported by simple analytical expressions.

A simple circuit composed of conventional electrical elements is shown to be a good approximation to the resistively shunted junction model of a superconducting weak-link whenever the junction draws a time-average supercurrent which is a small fraction of its maximum value. This simplified model can be used to obtain well-known results concerning the behaviour of weak-links when connected to external circuits.

The relation between the deflection aberrations and winding distribution of a scanning system is briefly reviewed and the importance of the cosine-distributed coil is pointed out. The winding distribution of the saddle-type deflection coil is completely Fourier-analysed, including the end effect and formulae are given for calculating the Fourier components of an air-core deflection field. A new type of corrector coil is proposed to eliminate the end effect. The equations of motion of Gaussian rays including third-order perturbations are shown. The method developed is applied to evaluating the aberrations of a Vidicon tube printed scanning coil and to designing a new scanning system for microfabrication. The Fourier decomposition technique developed reduces the three-dimensional magnetic field calculation to a two-dimensional one.

A complex analysis of the stress in cylindrical superconducting coils with anisotropic structures and without reinforcement is presented. The stresses in the coil result from the pretension at winding from the cooling down to low temperature due to the unequal thermal contraction of the components and from the magnetomechanical forces when current flows in the conductor. The anisotropic structure of the coil is represented through equivalent elastic moduli. The derived formulae are verified by tests on a model coil. The results show satisfactory agreement.

The value of the shear coefficient K used in Timoshenko's differential equation for flexural vibrations of beams has been experimentally assessed. For specimens of rectangular cross-section, K has been determined over a wide range of inverse slenderness ratios and for up to the fifth harmonic overtone of flexural vibration. It is shown that the expression of K=(5+5 nu )/(6+5 nu ) and K=(6+12 nu +6 nu ²)/(7+12 nu +4 nu ²), where nu is Poisson's ratio, for rectangular and circular cross-sections respectively, yield excellent agreement between theory and experiment.

A comprehensive study of dislocations in the K₂O-SrO-Nb₂O₅ system has been carried out and the etchants (i) HF (48%) and (ii) a mixture of H₂SO₄ (95%), HNO₃ (70%) and HF (48%) in the ratio 5:2:2 by volume were found effective in revealing dislocations on (001) cleavages of this system. Two types of pits, deep and shallow, and well-defined pyramidal etch hillocks were observed on the same surface on etching with HF. A comparative study of the etch patterns of the two etchants has also been made. The results are analysed and their implications are discussed.

An experimentally useful relation for the dependence of the apparent viscosity on the shearing force is derived. Reasonable simplifying assumptions are introduced into the continuum theory and the asymptotic behaviour of the apparent viscosity for a large shearing force is then derived.

An expression has been derived in the light of X-ray peak-shift analysis of cubic structures by Wagner (1966), to estimate the average residual internal stresses and lattice parameter changes in hexagonal systems from measurements of relative peak-position displacements in a powder diffractometer. This has been applied to several vacuum-evaporated zinc films ( approximately 20-500 nm thick), prepared at room temperature (25 degrees C) at a residual air pressure approximately 5*10^-5 Torr from a normal source. Considering the first four reflections, namely 00.2, 10.0, 10.1 and 10.2, the analysis shows that the films exhibit appreciable residual internal stresses sigma (tensile) lying in the range 1.185-0.569*10⁹ N m^-2 ( approximately 17 to 8*10⁴ psi), which decrease gradually with increasing thickness. The thermal stresses being small, residual internal stresses appear to be mostly due to the intrinsic stresses originating from lattice imperfections in the films. The lattice parameter changes ( Delta a, Delta c) are relatively small, and close to the experimental error limits.

The single-crystal material has a resistivity at 300 degrees C of 4.7 Omega cm and an activation energy of 0.13 eV. In the polycrystalline case it has been possible to separate out the bulk and grain boundary contributions to the total electrolyte resistance. These have activation energies of 0.15 and 0.26 eV respectively. The grain boundary or intergranular contribution becomes negligible above 200 degrees C and the sample resistivity at 300 degrees C is 15.4 Omega cm. The resistivity results obtained were independent of the electrode material used although this did affect the measured interfacial capacitance.

Using radioactive tracer techniques, the diffusion coefficient of the sodium ions has been determined from room temperature to 600 degrees C. These diffusion results have then been compared with the ionic conductivity of similar beta "-alumina material. From this comparison a determination of the Haven ratio (H_R) has also been made and a simple model is proposed that adequately predicts the observed magnitude of H_R.

Boron and phosphorus atoms were implanted into pure pyrolytic SiO₂ films, and their infrared absorption spectra were determined. The IR absorption bands of B-O and P-O bonds appeared in the spectra of the films, if the B and P ion doses were higher than 3*10¹⁶ atoms/cm². The effect of heat treatment on the formation of B-O and P-O bonds from B and P atoms implanted into SiO₂ films was examined. The results were used to determine the constant of the quantitative IR measurement of boron and phosphorus, as well as the absorption cross-section of the B-O and P-O bonds. The obtained constants of the B and P measurements, as well as the absorption cross-sections, were compared with those obtained by measuring the characteristics of diffused layers produced with pyrolytically doped oxide films.

The impulse electric strength of polythene film has been measured with and without a prestressing direct voltage of opposite polarity to that of the breakdown impulse after heating the polymer at several temperatures between 20 and 100 degrees C and quenching to room temperature. The steady-state electrical conduction through similar film specimens following identical heat treatment has also been measured. There was a correlation between breakdown strength with prestress, electrical conduction, and morphology as evinced by density changes.

On the basis of the condition of instability of cracks in a stressed body it is reported that the kinetics of triboluminescence in a crystal at a strain rate r can be expressed by the relation I=I₀r²t² exp(-t/ tau )-C₁, where C₁ is a constant. The value of the mechanical relaxation time tau of sugar crystals has been determined from triboluminescence measurements using the above relation and it has been found to be between 0.9 and 1.1 ms for different values of the strain rate of the crystal. It has been shown that a major portion of TBL in sugar crystals is due to the discharge of gases between the newly created surfaces of crystals during their fracture; however, some portion is due to other processes taking place in the crystal.