A technique is described and demonstrated to measure the size of spherical particles of known index of refraction by laser light scattering with an accuracy of better than 1%. This technique entails imaging the angular scattering intensity onto a photodiode array and applying a fast Fourier transform to the array output to obtain a frequency and phase corresponding to the number and angular position of the scattering lobes. Errors associated with particle trajectory effects and changes in the index of refraction are also considered. Results are not affected by the former, whereas variations of the refractive index by 2%, as may be typical, for example, of the transient heat up of a liquid hydrocarbon droplet, cause a deterioration of sizing accuracy to approximately 3%. The technique can in principle be applied in real time at data rates as high as 20-30 kHz with a modest equipment investment. Therefore, the measurement of droplet evaporation rates in dilute sprays with unprecedented accuracy appears to be feasible.

To support experiments scheduled for the First United States Microgravity Laboratory (USML-1) shuttle mission, experimental and computer simulation methods have been developed which allow ground-based investigation of the translational, rotational, and vibrational motions of single and dual liquid drops in an external acoustic field in a microgravity environment. The acoustic fields used are the 3-D orthogonal resonant modes of a rectangular chamber. Hardware and software development are described in detail. Results for the translation of single and dual drops are presented, and semi-automated schemes for controlled translation are proposed, tested, and evaluated.

The purpose of this study is to predict the ripeness of watermelon by the hitting sound. It was found that the reverberation time, the thickness of the skin, and the volume of the pulp were significantly correlated with ripeness. The hitting of watermelon can be explained as a damped oscillation, and this was verified through experiments and simulations, and correlation analysis between reverberation time and ripeness. As a result, the reverberation time was selected as an important variable. CNN was used to develop a model that predicts ripeness through the hitting sound of watermelon, which showed 99% accuracy. 4-layer perceptron model using the reverberation time which was selected as an important variable for predicting ripeness was developed. This showed 95.7% accuracy, in conclusion proposing an objective and non-destructive method to determine watermelon ripeness.

BACKGROUND Ultrasonic techniques, which measure elastic anisotropy, have been used to study texture and plastic anisotropy of sheet materials. Ultrasonic velocity measurements can determine the orientation distribution coefficients (ODCs) W 400, W 420, and W 440 which are used to describe crystallographic orientation distributions [1]. For steel sheets, strong correlations have been observed between ultrasonic velocity and the formability parameters i' and Ar [3]. The results for aluminum show a relationship between the ODC W 440 and the degree of earing [2-3]. In addition to a metal sheet's formability and degree of earing, information about individual texture components is also needed in certain cases. A Goss component, for example, is necessary in the manufacturing of quality steel transformers but undesirable in plate forming and canning applications. Recent work suggests that W 440 can indicate the presence of the cube texture verses deformation textures (brass, copper, S, etc.) [4]. Few studies are available, however, which attempt to distinguish between the various textures. This paper presents some initial results on ultrasonic texture identification of aluminum sheets using the distinctive features captured within the slowness (or inverse velocity) curves. We begin with theoretical predictions of Lamb wave slowness curves of perfect textures (cube, Goss, brass) and compare them with measurements taken from two aluminum samples by an electromagnetic acoustic transducer (EMAT) system. A second set of measurements from a laser-based ultrasonic setup (for which theory has not yet been formulated) is then presented and discussed in the context of developing an on-line system used for texture screening.

To support experiments scheduled for the First United States Microgravity Laboratory (USML-1) shuttle mission, experimental and computer simulation methods have been developed that allow ground-based investigation of the translational, rotational, and vibrational motions of single and dual liquid drops in an external acoustic field in a microgravity environment. The acoustic fields used are the 3-D orthogonal resonant modes of a rectangular chamber similar to the near ambient chamber of the drop physics module which will fly on USML-1. Results for the translation of two drops, and oscillation and rotation control of single drops will be presented. A software package allowing the simulation of actual manipulations to be performed for the flight experiments will be displayed. [Work supported by NASA through JPL Contract 958722.]