State Estimation For An Agonistic‐Antagonistic Muscle System

Research on assistive technology, rehabilitation, and prosthetics requires the understanding of human machine interaction, in which human muscular properties play a pivotal role. This paper studies a nonlinear agonistic‐antagonistic muscle system based on the Hill muscle model. To investigate the characteristics of the muscle model, the problem of estimating the state variables and activation signals of the dual muscle system is considered. In this work, parameter uncertainty and unknown inputs are taken into account for the estimation problem. Three observers are presented: a high gain observer, a sliding mode observer, and an adaptive sliding mode observer. Theoretical analysis shows the convergence of the three observers. Numerical simulations reveal that the three observers are comparable and provide reliable estimates.     

Multi- Objective Optimal Design of on- Demand Pressurized Irrigation Networks

In the context of water as an economic good, from the use of water, one can derive a value, which can be affected by the reliability of supply. On-demand irrigation systems provide valuable water to skilled farmers who have the capacity to maximize economic value of water. In this study, simultaneous optimization of on-demand irrigation network layout and pipe sizes is considered taking into account both investment and annual energy costs. The optimization problem is formulated as a problem of searching for the upstream head value, which minimizes the total cost (investment and energy costs) of the system. The investment and annual energy costs are obtained in two separate phases. Max–Min ant system (MMAS) algorithm is used to obtain the minimum cost design considering layout and pipe diameters of the network simultaneously. Clement methodology is used to determine flow rates of pipelines at the peak period of irrigation requirements. The applicability of the proposed method is showed by re-designing a real world example from literature.     

Al2O3–Water nanofluid heat transfer and entropy generation in a ribbed channel with wavy wall in the presence of magnetic field

In this article, a parametric study is conducted to evaluate heat transfer enhancement in a ribbed channel containing Al₂O₃–Water nanofluid with wavy wall. The physical domain is under the influence of the magnetic field that creates a negative force against the working fluid to move. Nanofluid with higher temperature enters the cool ribbed duct and heat is exchanged along the walls of channel. The effects of the dominant parameters including number of the blocks, solid volume fractions of nanofluid, Hartmann number, Reynolds number, and different states of amplitude sine waves are numerically tested on the local and average Nusselt number, skin friction, and total entropy generation. Excellent agreement between present study and previous literature is observed. It is found that, an augmentation in magnetic field will result in higher values of both local and average Nusselt number accompanying with bigger values of skin friction and entropy generation. Computations illustrate that, increasing the solid volume fraction of the Al₂O₃ nanoparticles will raise the Nusselt number and total entropy generation rate but its effect on the skin friction is negligible. Also, numerical results imply that increasing amplitude sine waves of the geometry has incremental effect on the Nusselt number and skin friction but its effect on the total entropy generation rate is not so clear. Moreover, by adding number of the used blocks in the presence of magnetic field, the local Nusselt number experiences more jumps but it does not increase the average Nusselt number, necessarily. In addition, using more blocks increases skin friction but it has a reverse effect on the total entropy generation rate.     

Loofa immobilized Bacillus sp. DSM 2523 as a whole cell biocatalyst for production of cyclodextrin glucanotransferase in an airlift reactor with a net draft tube

Cyclodextrin glucanotransferase (CGTase) production was studied using loofa-immobilized Bacillus sp. DSM 2523 and starch substrate. The bacterial cells from 2- and 4-day old cultures were used in the flask studies. Loofa and chitosan were added for cell immobilization and cell flocculation, respectively, and different treatments were considered according to the timing of their addition. The cell responses were evaluated for their degree of cell immobilization and level of CGTase activity. With the use of the selected treatment, testing was carried out in an airlift reactor with a net draft tube having specific geometric properties. The cell capacity for reusability also was examined. The production of CGTase was higher in the second cycle in the reactor operated at 0.25 vvm where the enzyme activity reaching 0.20?U/ml within 2?h. In the flask experiments, CGTase activity reached 0.23?U/ml after 19?h in the second cycle.     

Processing and characterization of elastomeric polycaprolactone triol–citrate coatings for biomedical applications

In this paper we describe the synthesis, processing and characterization of a novel elastic polyester coating created by carrying out catalyst-free polyesterification between biocompatible and non-toxic multifunctional reactants, namely polycaprolactone triol and citric acid. The physico-chemical and surface properties of the resulting polyester coatings and films have been investigated. This new material has been characterized by matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-ToF-MS), nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infra-red spectroscopy (FTIR), water-in-air contact angle measurements, scanning electron microscopy (SEM), thermal analysis (DSC), mechanical tests and swelling experiments. The polymer structure, surface properties (morphology and chemistry), mechanical integrity and hydration of the elastomer can be controlled by simple variation of the initial citric acid concentration in the polymer formation. This feature of the novel polyester material presents a significant development in the production of advanced coatings for biomedical applications.     

Practical Output Regulation of Uncertain Strict‐Feedback Form Systems

In this paper, an output feedback control is proposed to solve the practical output regulation problem of a class of nonlinear systems. In the first step of the design procedure, two sets of coordinate transformations are used to convert the output regulation problem of the system in the strict‐feedback form into the regulation problem of the transformed system in the uncertain normal form. Then, for the resulting system, a state feedback in the cast of nested sliding mode control is designed. Finally, by using the nonlinear separation principle, the output feedback controller is achieved by substituting the estimated states, resulting from the high‐gain observer, instead of real states. It can be shown that the states of the closed‐loop system are ultimately bounded. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society