Robust controller synthesis via non-linear matrix inequalities

Over thelastseveralyears fixed-structure multiplier versions of mixed structured singular value(MSSV) theory have been developed and have led to the development of linear matrix inequalities (LMIs) for the analysis of robust stability and performance. These LMIs have in turn led to the development of bilinear matrix inequalities BMIs for the synthesis of robust controllers. The BMI formulation in practice requires the multiplier to lie in the span of a stable basis, potentially introducing significant conservatism. This paper uses the LMI approach to MSSV analysis to develop an approach to robust controller synthesis that is based on the stable factors of the multipliers and does not require the multipliers to be restricted to a basis. It is shown that this approach requires the solution of non-linear matrix inequalities (NMIs). A continuation algorithm is presented for the solution of NMIs. This algorithm may be used to solve NMIs in general and its usefulness is not limited to the robust controller synthesis problem alone. The primary computational burden of the continuation algorithm is the solution of a series of LMIs. The use of this algorithm is demonstrated by designing a robust controller for a benchmark problem.     

A laboratory study for the treatment of arsenic, iron, and manganese bearing ground water using Fe(3+) impregnated activated carbon: effects of shaking time, pH and temperature

This paper deals with the experimental investigation related to removal of arsenic from a simulated contaminated ground water by the adsorption onto Fe(3+) impregnated granular activated carbon (GAC-Fe) in presence of Fe(2+), Fe(3+), and Mn(2+). Similar study has also been done with granular activated carbon (GAC) for comparison. The effects of shaking time, pH, and temperature on the percentage removal of As(T), As(III), As(V), Fe(2+), Fe(3+), and Mn have been discussed. The shaking time for optimum removal of arsenic species has been noted as 8h for GAC-Fe and 12h for GAC, respectively. As(T) removal was less affected by the change in pH within the pH range of 2-11. Maximum removal of As(V) and As(III) was observed in the pH range of 5-7 and 9-11, respectively, for both the adsorbents. Under the experimental conditions at 30 degrees C, the optimum removal of As(T), As(III), As(V), Fe, and Mn are 95.5%, 93%, 98%, 100%, and 41%, respectively, when GAC-Fe is used. For GAC these values are 56%, 41%, 71%, 99%, and 98%. The adsorbent dose (AD) and its particle size (PS) for both GAC and GAC-Fe were 30 g/l and 125-150 mum, respectively. The initial arsenic concentration in the synthetic water sample was 200 ppb.     

Photoswitching and Thermoresponsive Properties of Conjugated Multi‐chromophore Nanostructured Materials

Conjugated multi‐chromophore organic nanostructured materials have recently emerged as a new class of functional materials for developing efficient light‐harvesting, photosensitization, photocatalysis, and sensor devices because of their unique photophysical and photochemical properties. Here, we demonstrate the formation of various nanostructures (fibers and flakes) related to the molecular arrangement (H‐aggregation) of quaterthiophene (QTH) molecules and their influence on the photophysical properties. XRD studies confirm that the fiber structure consists of >95% crystalline material, whereas the flake structure is almost completely amorphous and the microstrain in flake‐shaped QTH is significantly higher than that of QTH in solution. The influence of the aggregation of the QTH molecules on their photoswitching and thermoresponsive photoluminescence properties is revealed. Time‐resolved anisotropic studies further unveil the relaxation dynamics and restricted chromophore properties of the self‐assembled nano/microstructured morphologies. Further investigations should pave the way for the future development of organic electronics, photovoltaics, and light‐harvesting systems based on π‐conjugated multi‐chromophore organic nanostructured materials.     

Probabilistic Assessment of UPV Test Result of a Degasser Unit

The novelty of this paper is to address a fundamental characteristic of ultrasonic pulse velocity (UPV) test result called distribution pattern and development of a methodology to simplify non-normal distribution patterns of UPV into normal distribution domain for easy applicability of quality assurance criteria for practicing engineers. In this paper probabilistic assessment methodology of UPV test results collected from a de-gasser structure of a refinery in India is discussed. Detailed analysis is performed to identify the distribution characteristics of UPV. No conventional distribution type including normal distribution fitted for UPV test results. A further attempt is made to derive simplified normal distributions with two different modes from the empirical cumulative distribution function of in situ test results. This creates scope for application of existing normal distribution based quality assurance criteria to non-normal domain of UPV. Criteria of characteristic strength instead of mean value is proposed as a better parameter for estimation of the quality of the material. Detailed physical interpretation and justification for the methodology is discussed with mathematical reasoning. The method is discussed in reference to existing literature. It is shown that the method is applicable to derive quality assurance criteria where simple assumption of normal distribution is not valid for UPV. Thus the method has the potential to make UPV a more useful test based on statistical reasoning for application on full scale structures.     

Energy efficient multi-beacon guard method for periodic data gathering in time-synchronized WSN

Wireless Networks - In periodic data-gathering, sensors can switch on the transceiver only during packet transmission to save energy. Exact clock-synchronization is challenging to achieve because...     

Exploring the optical properties of exposed-core-based photonic-crystal fibers

Journal of Computational Electronics - A photonic-crystal fiber (PCF) based on the surface plasmon resonance (SPR) effect with low confinement loss and high sensitivity response is designed and its...     

Tracking Down a New Steroid‐Hydroxylating Promiscuous Cytochrome P450: CYP154C8 from Streptomyces sp. W2233‐SM

CYP154C8 from Streptomyces sp. has been identified as a new cytochrome P450 with substrate flexibility towards different sets of steroids. In vitro treatment of these steroids with CYP154C8 revealed interesting product formation patterns with the same group of steroids. NMR study revealed the major product of corticosterone to be hydroxylated at the C21 position, whereas progesterone, androstenedione, testosterone, and 11‐ketoprogesterone were exclusively hydroxylated at the 16α position. However, the 16α‐hydroxylated product of progesterone was further hydroxylated to yield dihydroxylated products. 16‐hydroxyprogesterone was hydroxylated at two positions to yield dihydroxylated products: 2α,16α‐dihydroxyprogesterone and 6β,16α‐dihydroxyprogesterone. To the best of our knowledge, this is the first report of generation of such products through enzymatic hydroxylation by a CYP450. In view of the importance of modified steroids as pharmaceutical components, CYP154C8 has immense potential for utilization in bioproduction of hydroxylated derivative compounds to be directly employed for pharmaceutical applications.     

Performance improvement of DC-DC converter using L-D-based modified GaN-FET driver

Bootstrap capacitor in FET gate driver plays an important role in the transient performance of the half bridge configured synchronous buck DC-DC converter especially in the top switch. In this paper, a new bootstrap capacitor based GaN-FET driver is proposed. This new GaN-FET driver is tested in a synchronous buck converter for performance verification like immunity, transient response, and voltage ringing. A comparison study with the existing LM5113 (Texas Instrument)–based driver for GaN-FET and IR2110-based Si-MOSFET driver on a DC-DC converter is carried out to show the performance improvement using the proposed GaN-FET driver. The simulation study is performed on spice-based NI-Multisim 14.1. Finally, the designed GaN-FET driver is tested on a 60-W synchronous buck DC-DC converter in open-loop and closed-loop configuration.     

Condensation of R-134a Vapor over Single Horizontal Circular Integral-Fin Tubes with Trapezoidal Fins

An experimental investigation has been carried out for the condensation of R-134a vapor on four single horizontal circular integral-fin tubes (CIFTs) made of copper. The fins are of trapezoidal shape and the fin density of these tubes has been varied systematically from 934 fpm to 1,875 fpm. All the experimental data have been acquired at the saturation temperature of 312.4 +/- 0.5 K. The CIFT with 1,560 fpm fin density has been found to be the best-performing tube, as it has provided an enhancement factor (EF) of the order of 5.6. The experimental results are in the best agreement with Honda and Nozu model. This model has predicted 80% of the experimental results in a range of 0-30%.