Stress-sensitivity mapping for surface acoustic waves on quartz

A model is presented, relating the velocity shifts of surface acoustic waves (SAW) to the six tensor components of quasistatic stresses. Stress sensitivity is then defined through six independent coefficients, whatever the origin of the stress (direct external forces, thermoelastic stresses) might be. These coefficients, depending on crystal anisotropy, are computed for different cut angles and propagation directions of quartz crystal, and represented as a contour-line mapping. The determination of SAW quartz cuts compensated for both planar isotropic stresses and first-order temperature effects make it possible to define a family of quartz cuts with potentially low stress and temperature sensitivities for oscillator applications.     

Intensive computer keyboard training programmes

An intensive computer keyboard training course, based on an information processing model of man, was tested on a variety of personnel in work. Over a one or two week period, 241 adult subjects were trained. Subjects achieved mean speeds of 7.1 words per minute (WPM) after the second and 13.7 WPM after the ninth lesson. Significant decreases in errors per minute (EPM) occurred from 2.67 to 1.78. Previous experience with a keyboard and being female were factors associated with enhanced keyboard operating performance. Compressing the ten lessons from two into one week reduced the effectiveness of the programme.