A Saturating Extension of an Output Feedback Controller for Internally Damped Euler‐Lagrange Systems

In this research, a novel extension of the passivity‐based output feedback trajectory tracking controller is developed for internally damped Euler‐Lagrange systems with input saturation. Compared with the previous output feedback controllers, this new design of a combined adaptive controller‐observer system will reduce the risk of actuator saturation effectively via generalized saturation functions. Semi‐global uniform ultimate boundedness stability of the tracking errors and state estimation errors is guaranteed by Lyapunov stability analysis. An application of the proposed saturated output feedback controller is the stabilization of a nonholonomic wheeled mobile robot with saturated actuators towards desired trajectories. Simulation results are provided to illustrate the efficiency of the proposed controller in dealing with the actuator saturation.     

Submicron nanoporous polyacrylamide beads with tunable size for verapamil imprinting

Submicron sized polyacrylamide particles were prepared via modified precipitation polymerization method. Experimental design based on Taguchi approach was employed to study the influence of the polymerization composition including monomer (acrylamide), crosslinker (methylenebisacrylamide), initiator (azobisisobutyronitrile), and modifier (polyvinylpyrrolidone, K-30), on the size and morphology of the particles. Varying the polymerization composition, submicron-particles with sizes ranging between 100 and 600 nm were achieved. In all the cases, polydispersity index (PDI) of the particle size was found to be almost 1 indicating uniformity of the particle size. The concentration of crosslinker was found to be the most influential parameter on the particles size and the modifier concentration as an extra tunable parameter was believed to affect the nucleation mechanism and the viscosity of the medium to help controlling the particle size. To validate the optimization, particles with a preset diameter, i.e., 500 nm, were synthesized based on the composition predicted by the mathematical correlation. The polymer with the preset particle size was also imprinted with verapamil and characterized by FTIR, DSC, SEM, physisorption, elemental analysis, swelling, and batch rebinding experiments. The verapamil imprinted polymers bearing nano-cavities exhibited high affinity with imprinting factor 2.17 towards the target molecule. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A Flat Polymeric Membrane Sensor for Carbon Dioxide/Nitrogen Gas Mixture

A gas sensor was developed to measure the concentration of binary gas mixtures. This sensor works based on the permeability change of different gas mixtures across the polymeric membranes. Although high values of permeability and selectivity are needed for an ideal separation, the performance of this sensor mainly depends on the permeability factor. Polysulfone and silicone rubber were applied as the membrane base and coat, respectively. Moreover, in contrast to existing polymeric sensors that use hollow fibers, the present sensor is made of flat membranes. This new design is cheaper, smaller, and easier to use in comparison to the hollow fiber polymeric sensors. In order to test the sensor applicability, nitrogen and carbon dioxide were used as model gases. The effect of pressure on the response time and sensor accuracy was studied for the aforementioned gases. The response time (T_95%) of this low price sensor was 50?s, and the tolerance of measuring concentration was approximately 1.4% at 2?bar feed pressure. Also, increasing the feed pressure can improve the response time or accuracy of the sensor.     

Thermal,mechanical, and barrier properties of polyethylene/surlyn/organoclay nanocomposites blown films prepared by different mixing methods

(Low‐density polyethylene) (LDPE)/clay nanocomposites were prepared by melt blending in a twin‐screw extruder by using different mixing methods. Zinc‐neutralized carboxylate ionomer was used as a compatibilizer. Blown films of the nanocomposites were then prepared. The effect of mixing method on the clay dispersion and properties of the nanocomposites was evaluated by wide‐angle X‐ray diffraction analysis, mechanical properties, thermal properties, and barrier properties. The structure and properties of nanocomposites containing different amounts of nanoclay prepared by selected mixing techniques were also investigated. It was found that melt compounding of Surlyn/clay masterbatch with pure LDPE and Surlyn (two‐step‐a method) results in better dispersion and intercalation of the nanofillers than melt mixing of LDPE/Surlyn/clay masterbatch with pure LDPE and surlyn (two‐step‐b method) and direct mixing of LDPE with clay. The films containing ionomer have good barrier properties. A wide‐angle X‐ray diffraction pattern indicates that intercalation of polymer chains into the clay galleries decreases by increasing the clay content. Barrier properties and tensile modulus of the films were improved by increasing the clay content. In addition, tensile strength increased in the machine direction, but it decreased in the transverse direction by increasing the clay content. DSC results showed that increasing the clay content does not show significant change in the melting and crystallization temperatures. The results of thermogravimetric analysis showed that the thermal stability of the nanocomposites decreased by increasing the clay content more than 1 wt%. J. VINYL ADDIT. TECHNOL., 21:60–69, 2015. © 2014 Society of Plastics Engineers     

Multiobjective Calibration of Reservoir Water Quality Modeling Using Multiobjective Particle Swarm Optimization (MOPSO)

Water resource management encounters large variety of multi objective problems that require powerful optimization tools in order to fully characterize the existing tradeoffs between various objectives that can be minimizing difference between forecasted physical, chemical, and biological behaviors of model and measured data. Calibration of complex water quality models for river and reservoir systems may include conflicting objectives addressed by various combinations of interacting calibration parameters. Calibration of the two dimensional CE-QUAL-W2 water quality and hydrodynamic model is an excellent example where the model must be calibrated for both hydrodynamic and water quality behavior. The aim of the present study is to show how multiobjective particle swarm optimization (MOPSO) can be implemented for automatic calibration of water quality and hydrodynamic parameters of a 2-dimensional, hydrodynamic, and water quality models (CEQUAL-W2) to predict physical, chemical, and biological behaviors of a water body, and then focus on a relevant case study. So MOPSO is utilized to generate Pareto optimal solutions for two conflicting calibration objectives. A combined measure of thermal and reservoir water level is considered as the first calibration objective. The second objective is formulated to forecast the best physical, chemical, and biological behavior of the model. Realizing the strong interactions between water quality and hydrodynamic issues of water bodies and their dependencies on the same set of calibration parameters, the proposed multiobjective approach may provide a wide version of all possible calibration solutions for better decision making to select best solution from pareto front.     

Transbuccal delivery of acyclovir: I. In vitro determination of routes of buccal transport

PURPOSE: To determine the major routes of buccal transport of acyclovir and to examine the effects of pH and permeation enhancer on drug permeation. METHODS: Permeation of acyclovir across porcine buccal mucosa was studied by using side-by-side through diffusion cells at 37 degrees C. The permeability of acyclovir was determined at pH range of 3.3 to 8.8. Permeability of different ionic species was calculated by fitting the permeation of data to a mathematical model. Acyclovir was quantified using HPLC. RESULTS: Higher steady state fluxes were observed at pH 3.3 and 8.8. The partition coefficient (1-octanol/buffer) and the solubility of acyclovir showed the same pH dependent profile as that of drug permeation. In the presence of sodium glycocholate (NaGC) (2-100 mM), the permeability of acyclovir across buccal mucosa was increased 2 to 9 times. This enhancement was independent of pH and reached a plateau above the critical micelle concentration of NaGC. The permeabilities of anionic, cationic, and zwitterionic species were 3.83 X 10-5, 4.33 X 10-5, and 6.24 x 10-6 cm/sec, respectively. CONCLUSIONS: The in vitro permeability of acyclovir across porcine buccal mucosa and the octanol-water partitioning of the drug were pH dependent. A model of the paracellular permeation of the anionic, cationic, and zwitterionic forms of acyclovir is consistent with these data. The paracellular route was the primary route of buccal transport of acyclovir, and the enhancement of transbuccal transport of acyclovir by sodium glycocholate (NaGC) appeared to operate via this paracellular route.     

Disclosing the role of surface and bulk erosion on the viscoelastic behavior of biodegradable poly(ε-caprolactone)/poly(lactic acid)/hydroxyapatite nanocomposites

In this study, biodegradable polymer blends and their nanocomposites were prepared using poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) as blending components and hydroxyapatite (HA) nanoparticles as reinforcement. X-ray diffraction spectra showed that the presence of HA nanoparticles enhanced the intensity of the peaks (100) and (200) corresponding to the PCL's crystalline planes. The transmission electron microscopy images confirmed the high tendency of HA nanoparticles to locate in the PLA phase. The water uptake values of samples measured at pH 4 were more than those measured at other pH values. The weight loss behavior of blends in acidic medium was completely different from that in basic and neutral media. The Williams–Landel–Ferry equation and time–temperature superposition principle were applied to the creep compliance of the samples and their master curves were determined at reference temperature of 30 °C, and the mechanical properties of samples were predicted in other conditions. The effect of pH on the creep–recovery response of studied samples was analyzed. From this analysis, it could be found that at pH 4, the creep stain increased, while, at pH 7, there was no a significant change in the viscoelastic property. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47151.     

Approximation-based adaptive fault compensation backstepping control of fractional-order nonlinear systems: An output-feedback scheme

An observer-based adaptive fuzzy backstepping approach is proposed for nonlinear systems with respect to fractional-order differential equations, unmatched uncertainties, unmeasured states, and actuator faults. The approximation capability of fuzzy logic system and minimal learning parameter approaches are applied to identify uncertain functions in a simultaneous manner. For estimating the unavailable conditions, a fuzzy fractional-order state-observer is extended. Applying fault-tolerant approach in a backstepping design methodology would provide a new fault-tolerant adaptive fuzzy output-feedback approach for fractional-order strict-feedback systems. This control structure would assure the considered system stability through selection of the appropriate Lyapunov candidate function. Two numerical simulations are run to exhibit the validity herein.