Graphene network enabled high speed electrical actuation of shape memory nanocomposite based on poly(vinyl acetate)

Here strong electroactive shape memory nanocomposites were prepared by incorporating graphene nanoplatelets into poly(vinyl acetate) (PVAc ) through the simple solvent mixing method. TEM and XRD revealed that well exfoliated graphene nanoplatelets formed a continuous network throughout the matrix with a large amount of interconnectedness. Dynamic mechanical analysis showed that the inclusion of graphene significantly improves both glassy and rubbery moduli of the matrix. Furthermore, the prepared nanocomposites demonstrated a marked electrical conductivity up to 24.7 S m^?1 and thereby surprisingly rapid electrical actuation behaviour exhibiting a 100% recovery ratio in 2.5 s. Moreover, PVAc and its nanocomposites displayed scratch self‐healing capability. This work demonstrates that the PVAc /graphene nanocomposites with high modulus and excellent electroactive shape memory performance can be a promising material in many applications such as sensors and fast deployable and actuating devices. © 2016 Society of Chemical Industry     

Partially decomposed PVP as a surface modification of ZnO,CdO, ZnS and CdS nanostructures for enhanced stability and catalytic activity towards sulphamethoxazole degradation

In order to prepare stable and efficient photocatalysts, a microwave-furnace-assisted method using ethylene glycol (EG) as a solvent has been employed to obtain metal oxides and metal sulphides nanocatalysts with partial decomposition of the polyvinylpyrrolidone (PVP) cap (P-ZnO, P-CdO, P-ZnS and P-CdS); this associates the protective functionality of PVP with enhanced catalytic activity due to effective carriers transfer. The as-produced catalysts characterization revealed an extended growth of metal oxides compared with metal sulphides, which is attributed to the competition of EG as the source of oxygen with PVP to capsulate metal oxides during the synthesis. Infrared spectra confirmed the PVP–metal complexation and partial decomposition of the polymer. Metal sulphides exhibited a better catalytic activity compared with metal oxides for sulphamethoxazole degradation in UVC light owing to their size and morphology impact; further, P-CdS induced 71% antibiotic degradation after 10 h of illumination with visible light compared with only 48% for P-ZnS, 29% for P-ZdO and 20% for P-CdO due to improved light absorption. Interestingly, around 86% degradation was induced by mixing P-CdS with P-ZnS in 80:20% ratio, indicating an enhanced visible light activity due to improved electron–hole pair separation and high redox potential of P-ZnS.     

Investigation of Hydrodynamics of High‐Temperature Fluidized Beds by Pressure Fluctuations

Hydrodynamics of a gas‐solid fluidized bed at elevated temperatures was investigated by analyzing pressure fluctuations in time and frequency domains. Sand particles were fluidized with air at various bed temperatures. At a constant gas velocity, the standard deviation, power spectrum density function, and wide‐band energy of pressure fluctuations reach a maximum at 300 °C. Increasing the temperature to this value causes larger bubble sizes and after the bubbles reach their maximum size, they break into smaller bubbles. The Archimedes number decreases with higher temperature and the type of fluidization becomes closer to that of Geldart A boundary at this maximum temperature. Based on estimation of the drag force acting on the emulsion phase, it was concluded that 300 °C was a transition temperature at which the drag force reaches a minimum due to a significant change of interparticle and hydrodynamic forces.     

Survey of Motion Planning Literature in the Presence of Uncertainty: Considerations for UAV Guidance

This paper provides a survey of motion planning techniques under uncertainty with a focus on their application to autonomous guidance of unmanned aerial vehicles (UAVs). The paper first describes the primary sources of uncertainty arising in UAV guidance and then describes relevant practical techniques that have been reported in the literature. The paper makes a point of distinguishing between contributions from the field of robotics and artificial intelligence, and the field of dynamical systems and controls. Mutual and individual contributions for these fields are highlighted providing a roadmap for tackling the UAV guidance problem.     

Improved dynamic equations for the generally configured Stewart platform manipulator

In this paper, a Newton-Euler approach is utilized to generate the improved dynamic equations of the generally configured Stewart platform. Using the kinematic model of the universal joint, the rotational degree of freedom of the pods around the axial direction is taken into account in the formulation. The justifiable direction of the reaction moment on each pod is specified and considered in deriving the dynamic equations. Considering the theorem of parallel axes, the inertia tensors for different elements of the manipulator are obtained in this study. From a theoretical point, the improved formulation is more accurate in comparison with previous ones, and the necessity of the improvement is clear evident from significant differences in the simulation results for the improved model and the model without improvement. In addition to more feasibility of the structure and higher accuracy, the model is highly compatible with computer arithmetic and suitable for online applications for loop control problems in hardware.     

Gronwall inequality for hybrid systems

The Gronwall inequality, a well-known and useful result both for continuous-time and discrete-time signals, is extended to hybrid signals, namely those that combine continuous time and discrete time. An application of the result to establishing a bounded energy bounded state property for hybrid systems with inputs is provided.     

Controller Design Using Ant Colony Algorithm for a Non-inverting Buck–Boost Chopper Based on a Detailed Average Model

In this article, the non-inverting buck–boost converter and its operation modes are scrutinized. The closed-loop stability of the converter in buck and boost modes is analyzed, and the necessity of using an appropriated controller is demonstrated. Then the application of an adapted ant colony optimization to design a feedback controller is proposed, and a controller based on its existing model is tuned. Simulation and experimental results obtained from the ant colony optimization designed controller are then compared with a controller designed with the classic method. Although the simulation and experimental results prove the efficiency of the proposed control approach, a significant difference between controller behavior in practice and simulation is obvious. Finding these differences, more detailed models, including all parasitic elements, in the buck and boost modes are derived. Applying the proposed model in controller design illustrates that the desired performance of the converter can be guaranteed with a simple proportional-integral (PI) controller. The suggested ant colony-based controller is again tuned based on the more detailed model, which improves the performance of the converter system even more. Furthermore, good agreement between analytical and experimental outputs validates the accuracy of the modeling and simulation.     

Linear circuits: a measurement‐based approach

This paper proposes a new measurement‐based approach that can solve synthesis problems in unknown linear circuits. The method makes use of a small number of measurements to determine the functional dependency of any circuit signal or variable on any set of design variables. Once the functional dependency is obtained, the design requirements can be applied to find the design parameter values. The results are described for linear direct current and alternating current circuits. Copyright © 2013 John Wiley & Sons, Ltd.     

Non‐intrusive characterization of particle size changes in fluidized beds using recurrence plots

An on‐line method is developed for monitoring of mean particle size in fluidized beds using pressure fluctuations (PFs) and acoustic emissions (AE) signal by recurrence plot (RP) and recurrence quantification analysis (RQA). PFs and AE signals of a lab‐scale fluidized bed were measured simultaneously at various superficial gas velocities and mean particle sizes. Although the AE signals are often very complicated due to many different acoustic sources in the bed, applying RP analyses showed that small changes in mean particle size can be detected by visual comparison of AE‐RP structures, while this cannot be distinguished by graphical RP analysis of PFs. Moreover, the hydrodynamics of the bed was inspected through RQA analysis of both signals. For this purpose, recurrence rate, determinism, laminarity, average length of diagonal and vertical lines were extracted from RPs showing the effect of an increase in the mean particle size. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3547–3561, 2016