The good performance of olive mechanical harvesting by shaking depends on the suitable values of limb vibrator operating parameters (frequency and amplitude). Mathematical models of a single degree of freedom (S.D.F.M) and two degrees of freedom (T.D.F.M) were used to estimate the natural frequency (FN) of olive fruit stem system. The results from these models indicated that the FN values were 33.9, 31.9, and 28.0 Hz for the full mature stage, half-ripe olive, and full-ripe olive respectively. Branch vibrator was operated at three levels of frequency 25, 30 and 35 Hz and 3 levels of amplitude 25, 30 and 35 mm at a vibration time of 10 s. Measurements covered the fruit removal percentage (FRP) and degree of full-ripe fruit selectivity (DS). The results showed that the maximum FRP value, 90.6%, was achieved at a frequency of 35 Hz and amplitude of 25 mm while the maximum DS value, 78.58%, was obtained at 25 Hz frequency and 25 mm amplitude.

Three modification of the Hargreaves and Samani (HS) model were proposed to account for the effect of the atmospheric vapor on the prediction of the global solar radiation. The predicted values of the solar radiation using the three models and the values of the original HS model were compared to the measured solar radiation using root mean square error (RMSE), mean absolute bios error (MABE), mean bios error (MBE) and the T-test in pairs. The results showed that the first model M1, and the second model M2 performed better than the original HS. The T-test results showed that there are no significant differences between the means values of the two models prediction and the mean value of the measured solar radiation. The MBE for both M1 and M2 indicates a tendency to slightly over estimate the solar values for M1, and a slight under estimation of the M2 prediction. The model M1 increased the values of the ETo predicted using the FPM than the original HS model and thus solved the problem of ETo under estimation by FPM. It is recommended to use M1 for application where over predictions is safer such as evapotranspiration prediction and use M2 where under prediction is safer such as solar radiation prediction for thermal solar application and solar collectors.

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