Composite fault reconstruction and fault-tolerant control design for cyber-physical systems: An interval type-2 fuzzy approach.

This article scrutinizes the stabilization and fault reconstruction issues for interval type-2 fuzzy-based cyber-physical systems with actuator faults, deception attacks and external disturbances. The primary objective of this research is to formulate the learning observer system with the interval type-2 fuzzy technique that reconstructs the actuator faults as well as the immeasurable states of the addressed fuzzy based model. Further, the information of reconstructed actuator faults is incorporated in the developed controller with the imperfect premise variables for ensuring the stabilization of the system under consideration. At the same time, the H∞ technique is employed to reduce the impact of external disturbances in the considered model. In addition to that, the deception attacks are represented as a stochastic variable that satisfies the Bernoulli distributions. On the ground of this, a set of sufficient criteria is deduced in the context of linear matrix inequalities to affirm the stability of the addressed systems. Furthermore, the requisite gain matrices are computed by resolving the obtained linear matrix inequality based stability criteria. At last, two simulation examples, including the mass-spring-damper system are exhibited to demonstrate the usefulness of analytical findings of the developed strategy.

Design of robust tracking and disturbance attenuation control for stochastic control systems.

The focus of current research is to address the problem of robust output tracking, input delay compensation and disturbance attenuation performance for a family of stochastic systems by implementing the improved-equivalent-input-disturbance (IEID) estimator and the extended Smith predictor (ESP) technique. By integrating the observer and IEID-estimator together with ESP, a new closed-loop configuration is presented. Then, Lyapunov based mean-square asymptotic stability criterion is obtained. According to attained stability criterion, an IEID and ESP based-controller is designed, which ultimately guarantees the exact output tracking. Simulation studies of numerical examples are offered to expose the authenticity of IEID and ESP-based controller. Further, the proposed outcomes in comparison with existing results are presented to demonstrate the efficaciousness of the established control procedure.

Composite fault-tolerant and anti-disturbance control for switched fuzzy stochastic systems.

This paper investigates the issue of fault-tolerant and anti-disturbance attenuation for a two-dimensional modified repetitive control system (2D MRCS) which is described by switched fuzzy systems with multiple disturbances. In particular, the multiple disturbances contain an exogenous disturbance and standard Wiener noise. Specifically, a generalized extended state observer (GESO) is incorporated with the 2D MRCS to estimate both fault and exogenous multiple disturbances so that the disturbances and faults can be attenuated in the control input. Further, the improved 2D MRCS relaxes the stability condition and provides an enhanced tracking performance. Based on the Lyapunov function approach, pole placement technique and average dwell time approach, the stability criteria for the considered system is developed in terms of linear matrix inequality (LMI). Then an algorithm for designing a GESO-based 2D MRC design is developed based on the obtained LMIs. Further, the results developed are validated in the simulation section through three numerical examples.

Mechanical characterization of bio composite films as a novel drug carrier platform for sustained release of 5-fluorouracil for colon cancer: Methodological investigation.

In this study, we employed Pectin (PC) as a matrix that is hybridized with three different nucleobase (NB) units (cytosine, thymine, uracil) to generate pectin-nucleobase(PC-NB) biocomposite films stabilized through bio-multiple hydrogen bonds (BMHBs) as drug carrier for anticancer 5-Fluorouracil (5-FU). Prepared biocomposite films were characterized by Fourier Transform Infra-red Spectroscopy (FTIR), X-ray Diffraction (XRD), Thermogravimmetry Analysis (TGA) and Scanning Electron Microscope (SEM). Mechanical and sorption properties were also evaluated. In vitro drug release performed in both acidic pH 1.2 (stomach pH) and alkaline pH 7.4 (intestinal pH) showed that incorporation of nucleobases into pectin significantly restricted release rate of 5-FU particularly under acidic condition (pH 1.2). Hemolysis assays demonstrated that PC-NB-5-FU biocomposite film drug carriers were hemocompatible. Confocal microscope analysis indicates facilitated cellular uptake of PC-NB-5-FU film in HT-29 colon cancer cell line, which in turn result in a higher potential of apoptosis. Confocal imaging of fluorescent live/dead cell indicators and MTT assay outcomes, both demonstrated significant decreases in cellular viability of PC-NB-5-FU biocomposite films. Collectively, our findings indicate that this PC-NB-5-FU biocomposite films can be conferred as a proficient formulation for targeted delivery of colon cancer drugs.

Disturbance rejection in fuzzy systems based on two dimensional modified repetitive-control.

This paper concerns with the issues of designing an improved-equivalent-input-disturbance (IEID) based robust two dimensional modified repetitive control (2D MRC) for a class of fuzzy systems in the presence of aperiodic disturbances. Specifically, IEID-estimator is implemented to the 2D MRC systems that estimates all types of disturbances and compensates them for assuring robust stability. In particular, the proposed 2D MRC system has two different type of behaviours such as continuous control and discrete learning independently. To obtain gains of the observer and the controller, an adequate set of robust stability conditions is derived in the form of a linear-matrix-inequalities. Finally, simulation results for three numerical examples are provided to depict the efficacy of the proposed control technique.

Estimation and disturbance rejection performance for fractional order fuzzy systems.

This paper gives attention to the issues of output tracking and disturbance rejection performance for a class of fractional order Takagi-Sugeno fuzzy systems in the presence of time-varying delay and unknown external disturbances. More specifically, a new configuration of a fractional order modified repetitive controller that incorporates an improved equivalent-input-disturbance estimator and gain fluctuations in its design is proposed to perform disturbance rejection for the addressed system. By introducing a continuous frequency distributed equivalent model and using the Lyapunov-Krasovskii stability theory, a new set of sufficient conditions ensuring robust asymptotic stability of the resulting closed-loop system is obtained in the framework of linear matrix inequalities. Finally, a numerical example is presented to validate the developed theoretical results, where it is shown that the obtained conditions could force the considered system output to exactly track the given any kind of reference signal by compensating the unknown external disturbance.

Tuning biological properties of poly (vinyl alcohol) with amino acids and studying its influence on osteoblastic cell adhesion.

A new class of bio composite materials for orthopedic applications were prepared by blending polyvinyl alcohol (PVA) with certain amino acids (AA) such as glycine, lysine and phenyl alanine followed by in-situ cross-linking with citric acid (CT). CT cross-linked PVA offers sufficient chemical, thermal, and morphological stability by establishing intermolecular interaction. These biocomposite films were characterized for mechanical and thermal behaviors as well as analyzed through SEM, TGA and AFM studies. Zwitterionic characteristics of AA create cell-adhesive hydrophilic domains that act as potential cell-adhesion sites and facilitate osteointegration. Biocompatibility studies proved that PVA-AA/CT is non-toxic and exhibits good anti-bacterial activity. In-vitro bioactivity test and cell adhesion results predict that presence of AA is advantageous to enhance apatite growth and promote cell-substrate binding through modulating cellular activity of PVA polymer. Hydrophilicity of AA zwitterions significantly facilitates cell-substrate binding and CA cross-linking helps osteoblastic integration of PVA-AA/CT bio composite films. The rational design of microstructure with zwitterionic-hydrophilic domains is a key to enhance cell-substrate interaction of PVA-AAs/CT bio composites.

Fabrication and characterization of poly(vinyl alcohol)-TiO2 nanocomposite films for orthopedic applications.

Poly(vinyl alcohol) (PVA) is reinforced with TiO2 nanoparticles in order to enhance thermo-mechanical stabilities, surface characteristics and osteoblastic cell adhesion. PVA-TiO2 nanocomposite films with desirable mechanical, thermal and biocompatible properties are fabricated through solution casting method followed by de-hydrothermal cross-linking treatment. The composition of TiO2 nanoparticles was standardized to achieve mechanically stable nanocomposite films, based on tensile strength measurements composition of TiO2 is determined as optimal at 3wt%. PVA-TiO2 nanocomposite films were characterized by Scanning electron microscopy, Energy dispersive spectroscopy, Atomic force microscopy, Ultra violet and Fourier transform infrared spectroscopic techniques. Elemental mapping studies substantiate incorporation of TiO2 nanoparticles within the PVA matrix. Dimensional stability evaluated by soaking films in SBF for 24h insinuates the role of TiO2 in the direction of controlling degree of swelling. In-vitro bioactivity test and cell adhesion results also predict that presence of TiO2 is advantageous to enhance apatite growth and promote cell-substrate interaction. SEM studies illustrate improved surface morphology of PVA-TiO2 nanocomposite film with homogenously distributed TiO2 nanoparticles, which help to enhance thermo-mechanical behavior. TiO2 nanoparticles construct cell-adhesive hydrophilic nano-domains that act as potential cell adhesion sites and promotes osteointegration. Bio compatibility studies proved that thermally cross-linked PVA is non-toxic in relation to PVA cross-linked with glutaraldehyde. Cytotoxicity and cell adhesion of nanocomposite films evaluated through cell viability (MMT) assay and crystal violet staining revealed that PVA-3wt% TiO2nanocomposite could act as an excellent composite and hence suitable to be used in bone implant applications.

Simultaneous purification and spectrophotometric determination of nickel present in as-prepared single-walled carbon nanotubes (SWCNT).

The quality of single-walled nanotubes (SWCNT) is usually assessed by means of electron microscopic techniques or Raman spectroscopy. However, these sophisticated techniques are not widely available and do not reliably estimate the impurities in highly heterogeneous samples containing metal particles, fullerenes and other carbonaceous materials. We have developed a simple, inexpensive and convenient spectrophotometric method to assess the purity of arc-discharge grown as-prepared SWCNT. Purification process consists of initial gas phase oxidation and refluxing with nitric acid at the optimal conditions including short time period during acid refluxing. We have shown that this method could remove the metal particles effectively with a good yield of high quality SWCNTs, as shown by the spectrophotometric and scanning tunneling microscope studies described here. The extent of removal of the nickel present in as-prepared carbon nanotube sample is followed by spectrophotometeric analysis of the dissolved nickel analyte. The composition of nickel in the SWCNT sample is found to be 17.56%. The method is based on the chelating of Ni(2+) with dimethylglyoxime in ammoniacal citrate medium to form nickel dimethylglyoxime complex. A second stage purification of SWCNT eliminates the residual metal particles. The purified SWCNT has been studied using scanning tunneling microscopy which shows clearly resolved individual carbon nanotubes.

Effects of copper sulfate and copper nitrate in aquatic medium on the restoration potential and accumulation of copper in stem cuttings of the terrestrial medicinal plant, Portulaca oleracea linn.

The stem cuttings of the terrestrial, ornamental plant, Portulaca oleracea, grew well in distilled water by producing adventitious roots and leaves. However, when exposed to various concentrations of sulfate and nitrate salts of copper resulted in a suppression of root growth, increase in initiation time of roots and sprouts and decay of stem cuttings from the cut open end, decrease in number of leaves with an increase in concentration of copper in the growth medium. Accumulation of copper increased with increasing concentrations of both copper sulfate and copper nitrate. However, copper accumulation was greater in copper nitrate than in copper sulfate treatment. Hence, copper in the presence of nitrate is more toxic than in the presence of sulfate. The accumulation factors in all treatment concentrations were greater than 1, hence P. oleracea is a copper accumulator.