Microwatt shot-noise measurement

We report a simple scheme for sensitive measurements of optical-noise spectra. Optical noise is separated from electronic noise when the output of an analog spectrum analyzer is real-time squared and then lock-in detected. This method directly yields the desired mean-square noise voltage, i.e., the power spectrum of the optical noise on a linear scale. To demonstrate this technique, the mean-square shot noise of a laser beam is measured and found to vary linearly with the laser power from several milliwatts down to one microwatt, in excellent quantitative agreement with predictions.     

Fluorescence methods for determination of temperature in fuel sprays

Fluorescent additives which allow the determination of droplet temperatures in hydrocarbon fuel sprays have been developed. These systems, which exploit the chemistry of organic exciplexes; should make possible the determination of droplet temperatures within 1 degree C. Two specific systems are described: 3,10-dicyanophenanthrene/diethylaniline over the 20-135 degrees C range, and naphthalene/tetramethyl-p-phenylene diamine over the 140-265 degrees C range. These additives should allow 2-D real-time nonintrusive visualization of the droplet temperatures in an evolving fuel spray.     

The application of ergonomics to consumer product evaluation

Consumer products may be evaluated by technical tests or by ergonomics assessments. If an ergonomics assessment is required, then three types of test are available to the researcher. These are the user trial, the expert appraisal and the performance test. These three methods are described briefly and some advantages, disadvantages and issues arising from each are discussed. It is concluded that although the user trial will always assume an important role for the evaluation of many products, expert appraisals and performance tests can prove to be cost effective methods in certain circumstances. Some controversial areas requiring further research are highlighted.