Poly(vinylidene fluoride) (PVDF) and copolymers possess excellent ferro‐ and piezoelectric properties, and highly expected to be utilized as sensors in the areas covering the smart wearer, hydrophone, speaker, and medical ultrasonic devices. Besides PVDF in β crystalline phase, the copolymers with trifluoroethylene (TrFE) and tetrafluoroethylene (TFE) are widely investigated both in academia and industry. To illustrate how the steric hindrance between VDF and TrFE/TFE affects the condensed‐state structure and electric properties of the polymers, the electric properties and their dependences on molecular configuration and crystal structures of PVDF, P(VDF‐TrFE), and P(VDF‐TFE) are comparatively investigated. The introduction of same molar contents (20 mol%) of TrFE and TFE monomers into PVDF chain leads to the similar conformation transformation from α (γ ) phase to β phase and similar crystallinity in resultant P(VDF‐TFE) and P(VDF‐TrFE) thanks to the depressed energy of trans conformation and the increased energy barrier between anti‐gauche and trans conformation. That leads to the more preferred β‐phase and ferroelectric domains generated in P(VDF‐TrFE) and P(VDF‐TFE). Both the size of ferroelectric phase, the polarity of the polymer chain, the organization and orientation of the grains along the field are responsible for the excellent piezoelectric field resulted by the varied composition as well.
Orchard plant protection machinery in China still has a low application efficiency. Air-blast sprayers represent the primary development direction of pesticide applications in orchards. The spray control parameters have to be matched to the tree canopy status to achieve precise results. In this study, a vertical patternator was used to determine the accuracy of spraying fruit trees. The influences of three control parameters (blower speed, spray angle, and spray distance) on the spray performance of the air-blast sprayer were analyzed, and the volume of the spray was measured in collection plates at different heights. The quantitative relationship between the overall collection volume and the critical height collection volume was obtained for different parameter values, and the combined effects of any two control parameters on the collection performance and the position of the optimum collection area were obtained. The regression model describing the relationship between the collection volume in the critical height range and the three factors was established, and the main effects of the control parameters were determined. The results showed that if one parameter remained constant, the correlation between the other two parameters was non-significant. The collection volume in the critical height range increased initially and then decreased as the spray distance increased. The maximum collection volume was obtained at a spray distance of 1.762 m. The regression model can be used to obtain the optimum values of the parameters.
Moisture content (MC) directly affects the storage of apples. This study explored the prediction of MC and the shelf life of apples stored at room temperature. Using wavelengths selected by the competitive adaptive reweighted sampling algorithm and chemical kinetic reactions, a quantitative prediction model based on optical fiber spectroscopy and a kinetic model were established to determine the MC of apples stored at room temperature. The shelf life of apples was predicted based on the developed quantitative prediction and kinetic models. The determination coefficients of the calibration and prediction of the quantitative prediction model were determined as .9810 and .9686, with root mean square errors of .0020 and .0022, respectively, and a residual predictive deviation of 6.55. In addition, the correlation coefficient of the kinetic model was derived as .9957, with a root mean square error of .0011. Results demonstrate that when the MC of the fresh apples exceeds 85% and the initial MC of apples stored at room temperature equals 87%, the freshness preservation time of the apples should not exceed 28 days. The proposed quantitative and kinetic models are able to rapidly and accurately monitor the MC of apples, and the real-time prediction of apple shelf life can be realized according to the difference in the spectral information pre-and post-storage at room temperature. Practical ApplicationThis study provides a method for the determination of moisture content (MC) in apples and the prediction of shelf life based on kinetic models. According to the proposed method, enterprises can not only quickly and accurately detect the MC of apples to determine whether they are fresh, but can also easily predict the shelf life of apples to determine whether they are safe. | INTRODUCTIONApple is one of the most popular and important fruits worldwide. In particular, apple is favored by consumers because of its antioxidant, anti-aging, and immunity-enhancing functions (Briones-
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