Recently, hydrogels have been introduced for wastewater treatments as eco‐friendly and efficient adsorbents. Polyvinyl alcohol (PVA)‐based hydrogel reinforced with graphene oxide (GO) can be used for methylene blue (MB) removal from water. PVA/GO hydrogels (5 wt. % PVA and 0.5–2 wt. % GO) were prepared via the freeze‐thaw method, and the effect of GO weight percentage, freezing time, and cycle numbers were investigated. Regarding the results, the composite containing 1 wt. % GO, prepared by six‐hour freezing, and five cycles of freeze‐thawing, had the highest compressive strength (1.6±0.1 MPa) among the studied samples. Furthermore, by adding aloe vera to the PVA/GO composite containing 2 wt. % GO, the removal efficiency of MB was increased from 96 % to 99 % after 72 h, although the surface area was decreased from 31.6 m2 g−1 to 3.9 m2 g−1. Adsorption investigations were also highlighted PVA/GO and PVA/GO/aloe vera hydrogel composites follow the pseudo‐second‐order kinetics and Langmuir isotherm models.
The morphological and structural changes of an ablated flexible graphite in air and acetone ablation environments were studied here. From field emission scanning electron microscopy (FESEM) images, vertically aligned graphene nanosheets were found on the surface of ablated target in acetone. Measured ablation depth values for the ablated target in water were generally higher than those for the ablated target in air. X‐ray diffraction (XRD) analysis revealed that the (002) peak position and full width at half maximum (FWHM) of this peak in the ablated flexible graphite in the air increased. The gap between the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO), i.e., the band gap of the ablated target, indicating that the energy band gap of the ablated target in two ablation media increased compared to the nonirradiated target. Raman analysis from different points of the surface of the ablated target in both ablation media demonstrated the presence of bulk defects on the ablated target in the air, instead the edge defects were found for the ablated target in acetone. From Raman spectra, there were no single‐layer graphene nanosheets pinned on the surface of the target in acetone.
In this paper the modeling of a novel moving cable robot is conducted considering the vibration of the cables in its nonlinear format. The robot has 6 DOFs while the controlling input number is 12. Considering the fact that the elasticity of the cables is coupled with the dynamic model of the system, their vibration effects on the robot performance and accuracy. The target of this paper is to model the robot considering the cables’ elasticity and study its effect on the robot performance. This study can be considered in designing the controller of tower cranes and decrease the swing of the cables and increasing their stability. In order to cover the mentioned aim, the continuous vibration of the cables are modeled as a nonlinear system and it is added to the moving platform dynamics. Moreover the differences between the nonlinear modeling of the cables’ vibration and estimating them as a linear system is studied and their related results are compared and analyzed. The correctness of modeling is shown by comparing the results with previous research and the superiority of modeling the cables’ vibration in its nonlinear format is verified by the aid of a series of simulation scenarios in MATLAB. Moreover, by conducting some experimental test on the manufactured moving cable robot of IUST, it is illustrated that, modeling the cables in these robots as a nonlinear system results in more accurate results. It is shown that not only considering the cables’ vibration is significant in analyzing the robot dynamic, but also it is shown that promoting the mentioned model into nonlinear one increase the accuracy of the robot modeling which sequentially can provide a stronger controller for stabilizing and controlling the end-effector within a predefined trajectory.
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