Robust controllability and observability degrees of polynomially uncertain systems

This paper deals with the class of polynomially uncertain continuous-time linear time-invariant (LTI) systems whose uncertainties belong to a semi-algebraic set. The objective is to determine the minimum of the smallest singular value of the controllability or observability Gramian over the uncertainty region. This provides a quantitative measure for the robust controllability or observability degree of the system. To this end, it is shown that the problem can be recast as a sum-of-squares (SOS) problem. In the special case when the uncertainty region is polytopic, the corresponding SOS formulation can be simplified significantly. One can apply the proposed method to any large-scale interconnected system in order to identify those inputs and outputs that are more effective in controlling the system, in a robust manner. This enables the designer to simplify the control structure by ignoring those inputs and outputs whose contribution to the overall control operation is relatively weak. A numerical example is presented to demonstrate the efficacy of the results.     

Characterization of TiO2-coated ceramic foam prepared by modified sol-gel method and optimization of synthesis parameters in photodegradation of Acid Red 73

TiO₂ nanoparticles were synthesized by the P-25 powder modified sol-gel method under different TTIP (Titanium tetraisopropoxide) concentrations, P-25 loading and the gelation pHs. Structural properties of nanoparticles were characterized by XRD, FESEM and BET analysis. Results show that crystallinity level, particle size and the surface area are a function of P-25 loading and gelation pH, whereas TTIP concentration affects only the crystalline composition. Response surface methodology based on central composite design was used to optimize these synthesis parameters in photodegradation of Acid Red 73. The degradation efficiency was significantly affected by P-25 loading, pH value of gelation and the interaction effect between TTIP concentration and P-25 loading. The optimal values of parameters were found to be a pH of 1.34, a TTIP concentration of 0.25M and a P-25 loading of 39.76 g/L. At optimal synthesis conditions, TiO₂ film was coated on alumina foam and its structural properties were characterized by XRD, SEM and BET technique. The photocatalytic activity of the as-prepared films was found to be higher than that of the films prepared by the sol-gel method and those made from the slurries of P-25. The reasonable photocatalytic performance and good stability offered by the optimized film make it as an effective alternative for large application of water treatment.     

Evaluation of TiO2 Nanoparticles Concentration and Applied Current Density Role in Determination of Microstructural,Mechanical, and Corrosion Properties of Ni–Co Alloy Coatings

Protection of Metals and Physical Chemistry of Surfaces - The goal of the present investigation is to evaluate the influences of plating parameters such as TiO2 nanoparticles concentration in the...     

Fully Integrated Microscale Quasi‐2D Crystalline Molecular Field‐Effect Transistors

Monolithic integration of microscale organic field‐effect transistors (micro‐OFETs) is the only and inevitable path toward low‐cost large‐area electronics and displays. However, to date, such an ultimate technology has not yet evolved due to challenges in positioning and patterning highly crystalline microscale molecular layers as well as in developing micrometer scale integration schemes. In this work, by mastering the local growth of molecular semiconductors on pre‐defined terraces, single‐crystal quasi‐2D molecular layers tens of square micrometers in size are created in dense periodic arrays on a Si substrate. Nondestructive photolithographic processes are developed to pattern micro‐OFETs with mobilities up to 34.6 cm² V^?1 s^?1. This work demonstrates the feasibility to integrate arrays of short‐channel micro‐OFETs into electronic circuitry by highly parallel and size scalable fabrication technologies.     

Effects of Pb-Doping on Phase Structural and Optical Properties of CdZnS Nano-Powders

Cadmium zinc lead sulfide [Cd0.8（Zn1-x7,Pbx）0.2S] nano-powders were prepared by an improved coprecipitation method. The effect of Pb2＋ concentration at 500℃ on the phase and crystalline structure of the Cd0.8（Zn1-x7,Pbx）0.2S powders were investigated by X-ray diffraction （XRD）. According to the transmission electron microscopy （TEM） images, the particles size are in the range of 58 nm to 72 nm. In addition, optical band gap energy and optical constants of nano-powders were determined using the ultraviolet （UV） spectrum, Fournier transform infrared spectroscopy （FTIR）, and Kramers-Kronig analysis, respectively. We calculate the refractive index n, extinction coefficient k, and dielectric function t as a function of the wavenumber. The experiment results demonstrate that the amount of Pb＋2 has been playing an increasingly important role on optical properties of CZPS nanocrystals.     

Lycopene extraction from tomato processing waste using ultrasound and cell-wall degrading enzymes

The tomato processing wastes are rich in lycopene pigment, which can be consumed as a natural food colorant and bioactive ingredient. The present study investigates the appropriateness of ultrasound pretreatment and enzymatic treatment with cellulase and pectinase enzymes to extract lycopene pigment from tomato processing wastes using response surface methodology (RSM). To achieve this goal, a central composite design consisting of four independent variables including cellulase concentration (0–10%), pectinase concentration (0–5%), ultrasonic time (0–60 min) and pH (3.5–5.5) was used to examine the influences of these process variables on the lycopene extraction. The second order model of lycopene extraction obtained from RSM analysis had the p value less than 0.001 and represented a coefficient of determination (R²) of 93.82%. Thus, a satisfactorily agreement between experimental and predicted values for lycopene content obtained by the second order model was observed. In addition, the Fourier Transform Infrared spectroscopy results did not show any destruction of functional groups of the investigated extracts containing lycopene pigment. Scanning electronic microscopy images from the remaining tomato processing wastes after treatment with more lycopene content extraction demonstrated more porous structure. These results implied that ultrasound-assisted enzymatic extraction was an efficient extracting method.     

Overlapping control systems with optimal information exchange

This paper deals with the stabilizability of interconnected systems via linear time-invariant (LTI) decentralized controllers. Given a controllable and observable system with some distinct decentralized fixed modes (DFMs), it is desired to find a suitable control structure (in terms of information flow) for it. Since a decentralized controller consists of a number of non-interacting local controllers, the objective here is to establish certain interactions between the local controllers in order to eliminate the undesirable DFMs. This objective is achieved by translating the knowledge of the system into some bipartite graphs. Then, the notions of minimal sets and maximal subgraphs are introduced, which lead to a simple combinatorial algorithm for solving the underlying problem. The efficacy of the results obtained is demonstrated by an illustrative example.     

Fabrication of novel ZnO/BiOBr/C-Dots nanocomposites with considerable photocatalytic performances in removal of organic pollutants under visible light

In this study, ternary ZnO/BiOBr/C-Dots photocatalysts were successfully prepared by a simple strategy. Then, their characteristics such as structure, morphology, chemical, optical, textural, and photocatalytic performances were fully investigated. This study demonstrated that the ZnO/BiOBr/C-Dots nanocomposites showed remarkably increased photocatalytic performances compared with the ZnO and ZnO/BiOBr samples. In decolorization of RhB upon visible light, the highest activity was obtained when the volume of C-Dots was 0.25?mL, which was about 39.7 and 2.7?times premier than the ZnO and ZnO/BiOBr photocatalysts, respectively. In the ternary nanocomposites, the increased performance was mainly ascribed to the formed heterojunction between the counterparts, up conversion characteristics of C-Dots, and visible-light harvesting ability of BiOBr. The reactive species trapping experiments proved that O₂^? was the major species involved in the photocatalysis reaction. At last, the ternary nanocomposite displayed remarkable stability for recycling runs.     

Effect of MEA conditioning on PEMFC performance and EIS response under steady state condition

In this work, effect of three different commonly used on-line membrane-electrode assembly (MEA) conditioning procedures on the final MEA performance and electrochemical impedance spectroscopy (EIS) response was studied under different operation conditions. The conditioning methods were: constant voltage, constant current and US fuel cell council (USFCC) protocol.