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  • Author or Editor: Z. Láng x
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The possible effect of shaker harvest on root damage of 10-year-old cherry trees was studied on a simple tree structure model. The model was composed of elastic trunk and rigid main roots, the ends of which were connected to the surrounding soil via springs and dumping elements. Equations were set up to be able to calculate the relation between shaking height on the trunk and strain in the roots. To get the data for root break and their elongation at different shaking heights on the trunk, laboratory and field experiments were carried out on cherry trees and on their roots. Having evaluated the measured and calculated data it could be concluded that root damage is to be expected even at 3.6% strain and the risk of it increases with increased trunk amplitudes, i.e.

  1. with the decrease of shaking height
  2. at smaller stem diameters (i.e. in younger plantation), and
  3. if the unbalanced mass of the shaker machine is too large for the given tree size.

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Central leader and vase form tree models were built using Finite Element Modelling (FEM). Their main characteristics were chosen to be the same. To get comparable results to real values, acceleration versus time curves of the two types of real trees were processed using FFT method to determine their natural frequencies. The natural frequencies measured on real trees and calculated for the models have shown good similarity. The models were virtually exposed to the effect of horizontal forced vibration in the frequency range of 0–20 Hz. Acceleration-frequency curves were calculated and drawn to find the best frequency values for the highest accelerations and also to see their differences in the limb. For the same purpose, the direction of shaking was also changed. It was found that for the central leader limb shape multidirectional shaking would bring uniform detachment, while for the vase form trees, even the unidirectional shakers are appropriate. Real trees were also shaken and their acceleration-frequency curves were compared with the values of the FEMs. The resultant good similarity proves the ability of the models. The acceleration values achieved in the vase form models were much higher than for the central leader type. The acceleration-frequency curve of the shaker unit can be used to find the best frequency for shaking.

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Abstract  

Thermal analysis on two new heterometallic sulfide clusters, [PPh4]2[WS3(CuBr)3]2 and [PPh4]2[MoS3(CuBr)3]2 (where PPh4=tetraphenyl phosphonium, =pentamethylcyclopenta- dienyl), was carried out using a simultaneous TG-DTA unit in an atmosphere of flowing nitrogen and at various heating rates. Supplemented using EDS method, their thermal behavior and properties, together with the composition of their intermediate product, were examined and discussed in connection with their distinctive molecular structure as a dianion, which provided some theoretically and practically significant information. Both clusters decomposed in a two-step mode, but without a stable new phase composed of Mo/W-Cu-S formed during their decomposition process as we expected. Based on TG-DTG data, four methods, i.e. Achar-Brindley-Sharp, Coats-Redfern, Kissinger and Flynn- Wall-Ozawa equation, were used to calculate the non-isothermal kinetic parameters and to determine the most probable mechanisms.

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