Discrete-time output feedback sliding-mode control design for uncertain systems using linear matrix inequalities

An output feedback-based sliding-mode control design methodology for discrete-time systems is considered in this article. In previous work, it has been shown that by identifying a minimal set of current and past outputs, an augmented system can be obtained which permits the design of a sliding surface based upon output information only, if the invariant zeros of this augmented system are stable. In this work, a procedure for realising discrete-time controllers via a particular set of extended outputs is presented for non-square systems with uncertainties. This method is applicable when unstable invariant zeros are present in the original system. The conditions for existence of a sliding manifold guaranteeing a stable sliding motion are given. A procedure to obtain a Lyapunov matrix, which simultaneously satisfies both a Riccati inequality and a structural constraint, is used to formulate the corresponding control to solve the reachability problem. A numerical method using linear matrix inequalities is suggested to obtain the Lyapunov matrix. Finally, the design approach given in this article is applied to an aircraft problem and the use of the method as a reconfigurable control strategy in the presence of sensor failure is demonstrated.     

Response surface methodology for optimization of growth parameters for the production of carotenoids by a mutant strain of Rhodotorula gracilis

Response surface methodological studies of growth parameters for carotenoid production by a mutant strain of Rhodotorula gracilis (CFR 0-1) was carried out by a two-level fractional factorial design involving five variables, namely glucose concentration (%), incubation period (days), volume of inoculum (ml/100 ml), pH, and temperature (°C). The response equation developed indicated linear relationship between period of incubation, temperature, sugar concentration, and volume of inoculum on carotenoid production. A temperature of 24 °C was found to exhibit maximum carotenoid production in the mutant. The results indicated maximum carotenogenesis (0.09%) at 8% glucose level, with pH 7.5 and 6.0 ml/100 ml of inoculum for an incubation period of 12 days at 24 °C, which was also verified by experimental data.     

Self-assembled chloro-bridged metallo-prismatic cations of the general formula [M6(η-C5Me5)6(μ3-tpt)2(μ-Cl)6] (M = Rh, Ir; tpt = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine)

Two cationic pentamethylcyclopentadienyl metal-based hexanuclear complexes with trigonal prismatic architecture have been synthesised through a two-step strategy. The dinuclear complexes [M(η⁵- C₅Me₅)(μ-Cl)Cl]₂ (M = rhodium and iridium) react with 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (tpt) in dichloromethane to give the trinuclear complexes [Rh₃(η⁵-C₅Me₅)₃(μ₃-tpt)Cl₆] (1) and [Ir₃(η⁵-C₅Me₅)₃(μ₃-tpt)Cl₆] (2), respectively. Addition of silver triflate to 1 and 2 in dichloromethane connects two identical triangular panels to form the hexanuclear metallo-prismatic cations [Rh₆(η⁵-C₅Me₅)₆(μ₃-tpt)₂(μ-Cl)₆]⁶⁺ (3) and [Ir₆(η⁵-C₅Me₅)₆(μ₃-tpt)₂(μ-Cl)₆]⁶⁺ (4), respectively. Cations 3 and 4 have been isolated as their triflate salts and characterised by ¹H NMR, IR and UV/visible spectroscopy.     

Nematic Phases in 1,2,4‐Oxadiazole‐Based Bent‐Core Liquid Crystals: Is There a Ferroelectric Switching?

Four series of new 1,2,4‐oxadiazole derived bent‐core liquid crystals incorporating one or two cyclohexane rings are synthesized and investigated by optical polarizing microscopy, differential scanning calorimetry (DSC), X‐ray diffraction (XRD), electro‐optical, and dielectric investigations. All the compounds exhibit wide ranges of nematic phases composed of tilted smectic (SmC‐type) cybotactic clusters with strongly tilted aromatic cores (40–57°) and show a distinct peak in the current curves observed under a triangular wave field. Dielectric spectroscopy of aligned samples corroborates the previously proposed polar structure of the cybotactic clusters and the ferroelectric‐like polar switching of these nematic phases. Hence, it is shown that this is a general feature of the nematic phases of structurally different 3,5‐diphenyl‐1,2,4‐oxadiazole derivatives. In these uniaxial nematic phases there is appreciable local biaxiality and polar order in the cybotactic clusters. As a second point it is shown that electric field induced fan‐like textures, as often observed for the nematic phases of bent‐core liquid crystals, do not indicate the formation of a smectic phase, rather they represent special electro‐convection patterns due to hydrodynamic instabilities.     

Persistence and decontamination of surrogate radioisotopes in a model drinking water distribution system

Contamination of a model drinking water system with surrogate radioisotopes was examined with respect to persistence on and decontamination of infrastructure surfaces. Cesium and cobalt chloride salts were used as surrogates for cesium-137 and cobalt-60. Studies were conducted in biofilm annular reactors containing heavily corroded iron surfaces formed under shear and constantly submerged in drinking water. Cesium was not detected on the corroded iron surface after equilibration with 10 and 100 mg L⁻¹ solutions of cesium chloride, but cobalt was detected on corroded iron coupons at both initial concentrations. The amount of adhered cobalt decreased over the next six weeks, but was still present when monitoring stopped. X-ray absorption near-edge spectroscopy (XANES) showed that adhered cobalt was in the III oxidation state. The adsorbed cobalt was strongly resistant to decontamination by various physicochemical methods. Simulated flushing, use of free chlorine and dilute ammonia were found to be ineffective whereas use of aggressive methods like 14.5 M ammonia and 0.36 M sulfuric acid removed 37 and 92% of the sorbed cobalt, respectively.     

Enhancement of growth and coumarin production in hairy root cultures of witloof chicory (Cichorium intybus L.cv.Lucknow local) under the influence of fungal elicitors

Studies were conducted to determine the possible production of coumarins in hairy root cultures of Cichorium intybus L.cv.Lucknow local under the influence of microbial agents. Pythium aphanidermatum and Phytopthora parasitica var. nicotiana were cultured and their mycelial and medium filtrate were used for the elicitation of coumarin production. The media filtrate of P. parasitica at 1.0% v/v added to the MS basal medium led to the maximum growth of hairy roots of C. intybus, which was 1.57-fold higher than the untreated control on the 28th day of culture, along with maximum esculin and esculetin yields which were 4.06- and 3.71-fold higher than the control on the 28th day. The yields of esculin and esculetin in hairy root cultures of chicory strongly correlated with growth. To check the effect of these fungal elicitors on endogenous polyamine metabolism, titers of total endogenous polyamines were analyzed. It was confirmed that the media filtrate of P. parasitica at 1.0% v/v concentration resulted in maximum accumulation of total endogenous polyamines, wherein endogenous spermine titers were found to be maximum as compared to endogenous spermidine and putrescine titers on the 28th day. Total endogenous spermine in the case of 1.0% MF v/v P. parasitica was 1.3-fold higher than that of the control on the 28th day of culture. Maximum growth index with greater length of primary root (17.61±0.18 cm) and greater number of secondary and tertiary roots was recorded for the medium filtrate of P. parasitica at 1.0% v/v concentration. This study also provided an insight into the morphological changes in terms of branching patterns, occurring in roots under the influence of these fungal elicitors.     

Optimisation of growth parameters for the production of carotenoids by Rhodotorula gracilis

 Response surface methodological studies of growth parameters for carotenoid production by Rhodotorula gracilis (ATCC 90950) have been carried out for three parameters employed, namely glucose concentration (%), incubation period (days) and volume of inoculum (ml/100 ml). The results indicated maximum carotenogenesis (0.054%) at a 10% glucose level with a 2 ml/100 ml volume of inoculum for an incubation period of 9 days, which was also verified by experimental data. Received: 25 May 1998     

Curcumin loaded electrospun Bombyx mori silk nanofibers for drug delivery

Silk fibroin from Bombyx mori silk cocoons was electrospun into silk nanofibers (SNFs). SEM images show that 9% w/v of SNFs was smooth and beadless having an average diameter in the range 30–150 nm. Curcumin (0.5–1.5 wt%) was incorporated into the silk fibroin solution and electrospun to obtain curcumin incorporated silk nanofibers (CSNFs) with diameters between 50 and 200 nm. The dispersion of curcumin in the SNFs was confirmed by TEM. The amorphous nature of curcumin upon incorporation into SNFs was confirmed by XRD. The functional groups of SNF and CSNF were confirmed by Fourier transform infrared spectroscopy. The SNFs and CSNFs were thermally stable up to ca 350 °C as evidenced by TGA. The glass transition temperature (T_g) of SNFs (168 °C) increased to 184 °C in the case of CSNFs as confirmed by DSC. The storage modulus, loss modulus and tan δ were determined by dynamic mechanical analysis. The percentages of porosity and water uptake of SNFs were 85% and 150%, respectively. The percentage in vitro cumulative release of curcumin at the end of the tenth day for 0.5, 1 and 1.5 wt% formulations was 82%, 84% and 80%, respectively. © 2013 Society of Chemical Industry     

Enhancement of growth and coumarin production in hairy root cultures of witloof chicory (Cichorium intybus L.cv. Lucknow local) under the influence of fungal elicitors

Studies were conducted to determine the possible production of coumarins in hairy root cultures of Cichorium intybus L.cv.Lucknow local under the influence of microbial agents. Pythium aphanidermatum and Phytopthora parasitica var. nicotiana were cultured and their mycelial and medium filtrate were used for the elicitation of coumarin production. The media filtrate of P. parasitica at 1.0% v/v added to the MS basal medium led to the maximum growth of hairy roots of C. intybus, which was 1.57-fold higher than the untreated control on the 28th day of culture, along with maximum esculin and esculetin yields which were 4.06- and 3.71-fold higher than the control on the 28th day. The yields of esculin and esculetin in hairy root cultures of chicory strongly correlated with growth. To check the effect of these fungal elicitors on endogenous polyamine metabolism, titers of total endogenous polyamines were analyzed. It was confirmed that the media filtrate of P. parasitica at 1.0% v/v concentration resulted in maximum accumulation of total endogenous polyamines, wherein endogenous spermine titers were found to be maximum as compared to endogenous spermidine and putrescine titers on the 28th day. Total endogenous spermine in the case of 1.0% MF v/v P. parasitica was 1.3-fold higher than that of the control on the 28th day of culture. Maximum growth index with greater length of primary root (17.61+/-0.18 cm) and greater number of secondary and tertiary roots was recorded for the medium filtrate of P. parasitica at 1.0% v/v concentration. This study also provided an insight into the morphological changes in terms of branching patterns, occurring in roots under the influence of these fungal elicitors.     

Design and implementation of a sensor-based wireless camera system for continuous monitoring in assistive environments

Camera-based surveillance system is an important tool for assistive environment to monitor those who may have physical or cognitive impairment. It is, however, expensive to deploy a wired surveillance system and difficult to continuously monitor a moving subject in a large facility where many cameras are deployed. In this paper, we first evaluate the performance of streaming camera images over wireless networks in both residential and office environments and present the quantitative results to show the feasibility of using wireless backbones for camera surveillance systems. We then propose sensor-integrated camera surveillance (SICS) to address the continuous monitoring problem. SICS uses wearable wireless sensors to locate moving subjects and automatically selects the camera covering the subject, allowing human operators to focus on only one screen to monitor an individual. SICS uses a self-organizing wireless mesh network to allow flexible deployment at reduced cost. An on-board image-processing algorithm is used to reduce the bandwidth consumption. Through empirical evaluation, we found that the automatic camera hand-off enabled by SICS was effective for continuous camera monitoring and a sophisticated wireless network management system is required to deploy the SICS in practice.