| Summary: | 博士 === 國立臺灣大學 === 生物產業機電工程學研究所 === 93 === The injuries of fruits after harvest result in considerable degradation in quality. Injuries are caused by manhandling or mechanical operations in general. One of these causes is the vibration during transportation. Fruits are transported from orchard farms to an assembly yard of production-marketing groups by a maneuverable small-type agricultural transporter, and this is called the first stage of transportation. Well-packaged fruits are consigned to the distribution center by trucks and package dealt to retailers. Consumers then buy fruits from a retail market or outlet. This is the second stage of transportation.
To investigate the transportation of domestic fruits after harvest, this study tried to build up the field data acquisition system. The vibration data of the first and second stage transportation were measured and recorded and the curves of the power spectral density (PSD) were analyzed. In all of the tests, the magnitudes of PSD’s were found to be in descending order: the rear part of the main chassis beneath the truck-bed, the middle part of the main chassis, the frame beneath the driver’s seat and the front part of the main chassis. Besides, the inflation pressure had no significant influence on the vibration of the transporter. Meanwhile, the probability density function (PDF) and the power density function analysis’s were both feasible and consistent with each other in this research. A “multi-segments 2-degree polynomial regression with increasing sampling variability” technique was developed and carried out by MATLAB program in this study. Comparing the field data and the results of simulation, it showed that satisfactory coincidence existed in the shapes of the average PSDs and the frequency of peak signals. However, the peak values in higher frequency range showed some differences.
To combine the GPS and the field data acquisition system was a way to develop an effective working model of investigating the second stage of transportation and of recording the working process of horticultural produce by vibration. In order to evaluate the injury caused by vibration, the packaged Malaysian carambola was vibrated by the electro-dynamic shaker as the trip from Tainan county to Taipei city. The simulation of random vibration controlled by random profile of a small-type agricultural transporter in the conditions of regular tire pressure, farm road, 400 kg loading and velocity at 8.5 km/h ran for 20 minutes. The following procedure was a 20-minute mountain road trip and a 4.5 hr-trip on high way. Finally, a 30-minute trip was on the urban road. The result of the injured carambola by transport vibration revealed that the rage of carbon dioxide was different between the sets of treatment and the check. It could be an index of injured carambola. It was almost impossible to measure the ethylene quantity of samples after the simulation vibration. Therefore, the measurement of ethylene may not be suitable for a prompt indication.
The study could be a contribution of the investigation of the characteristic of vibration and the injury of fruits during transportation and can offer a way to reduce the damage and value loss of fruit.
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