Showing papers by "John C. Fothergill published in 1991"
TL;DR: In this article, a breakdown mechanism is proposed in which a filamentary-shaped crack propagates through a dielectric, releasing both electrostatic energy and electromechanical strain energy stored in the material due to the applied electric field.
Abstract: A breakdown mechanism is proposed in which a filamentary-shaped crack propagates through a dielectric, releasing both electrostatic energy and electromechanical strain energy stored in the material due to the applied electric field. The mechanism predicts a breakdown strength which is proportional to the fourth root of Young's modulus and a time to breakdown comparable with that taken for a sound wave to cross the dielectric ( approximately=0.1 mu s in 25 mu m thick polyethene films). Analysis of previously unexplained results of M. Hikita et al. (1985) on thin films of polyethylene yields good agreement with the proposed mechanism and a filament radius which is comparable to the gross morphological features of the dielectric. >
118 citations
23 Sep 1991
TL;DR: A system which scans electrocardiogram waveforms stored on paper and converts them to digital data stored on a computer enables quick and reliable measurements of QT intervals, thereby replacing the tedious and potentially insensitive method of hand measurements.
Abstract: The authors have developed a system which scans electrocardiogram (ECG) waveforms stored on paper and converts them to digital data stored on a computer. The system enables quick and reliable measurements of QT intervals, thereby replacing the tedious and potentially insensitive method of hand measurements. Preliminary results of comparison between hand and user-interactive measurements are presented to show the accuracy and characteristics of the system. >
15 citations