No description available.

Thesis (M.D.S.) -- University of Adelaide, Dept. of Dental Health, 1976.

No description available.

The effect of uni-directional stress on the electrode potential of copper in aerated potassium nitrate solutions was studied. The influence of the variables time, temperature, concentration, magnitude of stress, mechanical condition of the metal, and pH was considered. The potential difference between two size #22 B & S copper wires was continuously recorded on a type G Speedomax automatic recorder. A balance pan was attached to one of the wires to which weights were added and the change in the potential difference between the two wires from the pre-stress potential difference was taken as the strain potential. At least four runs, using fresh pairs of wires for each run, were carried out to illustrate each specific point and to show the results have statistical significance and are reproducible. The following results were obtained: (A) Electronegative strain potentials have been obtained for copper metal in aerated potassium nitrate solution; these changes achieve a maximum at the instant of stressing and then decay with a negative acceleration with time. After an initial period of time, the strain potential decayed logarithmically with time. The magnitude of the electronegative strain potential for a given stress increased exponentially with the reciprocal of the absolute temperature and remained essentially unchanged for concentration changes ranging from 0.005N to 0.500N. (B) Experimental evidence was obtained to support the postulate that strain potentials of copper metal in aerated potassium nitrate solution and their time dependence parallel film rupture; the effect of the change in internal energy due to plastic deformation cannot be ignored. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

D.Ing. (Electrical And Electronic Engineering) / Please refer to full text to view abstract

Call number: LD2668 .T4 1962 A82

Present-day builders of harpsichords disagree as to the use of iron or carbon-steel wire in their attempt to duplicate the tonal qualities of the early 16th century instruments. The variations in tone produced by vibrating iron and steel wires may be due, at least in part, to differences in their decay characteristics. A wire was set into vibration by placing a section in a magnetic field and passing a variable-frequency alternating current through it. A condition of resonance was established by appropriately selecting frequencies, lengths, and tensions that would simultaneously satisfy the relationship: fr = n/2L(T/p)1/2. Then measurements of decay time as a function of frequency were made for a variety of typical harpsichord strings: iron, steel, brass, bronze, etc. Samples varied in diameter from 170 mm to 600 mm and the resonant frequencies ranged from 20 Hz to 12,000 Hz. Changes in energy loss through the supports were measured by varying the size and mass of the supports and by modifying the method of attachment of the wire. Differences in loss of energy due to internal friction were noted in the comparison of decay times for different wire materials and diameters. The energy losses due to sound radiation and viscous damping were examined by placing the vibrating wire in a vacuum. Two significant conclusions, among others gathered from the data, indicate that: 1. For similar samples of iron and steel wire vibrating under like conditions, the steel wire will vibrate for a longer period of time than the iron wire. 2. Energy losses to sound radiation and viscous damping greatly exceed all other modes of energy loss from the wire. Suggestions for additional investigations based On the results of this paper are presented in the concluding pages.

The reliability of the main cable of a suspension bridge is crucial to the reliability of the entire bridge. Throughout the life of a suspension bridge, its main cables are subject to corrosion due to various factors, and the deterioration of strength is a slowly evolving and dynamic process. The goal of this research is to find the pattern of how the strength of steel wires inside a suspension bridge cable changes with time. Two methodologies are proposed based on the analysis of five data sets which were collected by testing pristine wires, artificially corroded wires, and wires taken from three suspension bridges: Severn Bridge, Forth Road Bridge and Williamsburg Bridge. The first methodology is to model wire strength as a random process in space whose marginal probability distribution and power spectral density evolve with time. Both the marginal distribution and the power spectral density are parameterized with time-dependent parameters. This enables the use of Monte Carlo methods to estimate the failure probability of wires at any given time. An often encountered problem -- the incompatibility between the non-Gaussian marginal probability distribution and prescribed power spectral density -- which arises when simulating non-Gaussian random processes using translational field theory, is also studied. It is shown by copula theory that the selected marginal distribution imposes restrictions on the selection of power spectral density function. The second methodology is to model the deterioration rate of wire strength as a stochastic process in time, under Ito's stochastic calculus framework. The deterioration rate process is identified as a mean-reversion stochastic process taking non-negative values. It is proposed that the actual deterioration of wire strength depends on the deterioration rate, and may also depend on the state of the wire strength itself. The probability distribution of wire strength at any given time can be obtained by integrating the deterioration rate process. The model parameters are calibrated from the available data sets by matching moments or minimizing differences between probability distributions.