An Independent Component Analysis Approach for Wide-Area Monitoring of Power System Disturbances

Abstract

Wide-area power system monitoring based on phasor measurement units allows collecting a set of physical variables for evaluating the system security and stability, as well as for detecting power system disturbances. However, trends, noise and non-Gaussian distribution in measurements are important challenges for carrying out the detection, localization and visualization of power system disturbances. In this paper, a methodology that combines independent component analysis with statistical indices for detecting and visualizing anomalous dynamic events from wide-area measurements is proposed. From the statistical indices, two charts are also proposed to provide a better understanding of the system disturbances. Finally, a set of simulated data obtained from a transient stability model of the New England/New York test system is used to demonstrate the effectiveness of the proposed technique.     

Phthalocyanine–Virus Nanofibers as Heterogeneous Catalysts for Continuous‐Flow Photo‐Oxidation Processes

The generation of highly reactive oxygen species (ROS) at room temperature for application in organic synthesis and wastewater treatment represents a great challenge of the current chemical industry. In fact, the development of biodegradable scaffolds to support ROS‐generating active sites is an important prerequisite for the production of environmentally benign catalysts. Herein, the electrostatic cocrystallization of a cationic phthalocyanine (Pc) and negatively charged tobacco mosaic virus (TMV) is described, together with the capacity of the resulting crystals to photogenerate ROS. To this end, a novel peripherally crowded zinc Pc (1) is synthesized. With 16 positive charges, this photosensitizer shows no aqueous aggregation, and is able to act as a molecular glue in the unidimensional assembly of TMV. A step‐wise decrease of ionic strength in mixtures of both components results in exceptionally long fibers, constituted by hexagonally bundled viruses thoroughly characterized by electron and confocal microscopy. The fibers are able to produce ROS in a proof‐of‐concept microfluidic device, where they are immobilized and irradiated in several cycles, showing a resilient performance. The bottom‐up approach also enables the light‐triggered disassembly of fibers after use. This work represents an important example of a biohybrid material with projected application in light‐mediated heterogeneous catalysis.     

Temporal Sampling of Enzymes from Live Cells by Localized Electroporation and Quantification of Activity by SAMDI Mass Spectrometry

Measuring changes in enzymatic activity over time from small numbers of cells remains a significant technical challenge. In this work, a method for sampling the cytoplasm of cells is introduced to extract enzymes and measure their activity at multiple time points. A microfluidic device, termed the live cell analysis device (LCAD), is designed, where cells are cultured in microwell arrays fabricated on polymer membranes containing nanochannels. Localized electroporation of the cells opens transient pores in the cell membrane at the interface with the nanochannels, enabling extraction of enzymes into nanoliter‐volume chambers. In the extraction chambers, the enzymes modify immobilized substrates, and their activity is quantified by self‐assembled monolayers for matrix‐assisted laser desorption/ionization (SAMDI) mass spectrometry. By employing the LCAD‐SAMDI platform, protein delivery into cells is demonstrated. Next, it is shown that enzymes can be extracted, and their activity measured without a loss in viability. Lastly, cells are sampled at multiple time points to study changes in phosphatase activity in response to oxidation by hydrogen peroxide. With this unique sampling device and label‐free assay format, the LCAD with SAMDI enables a powerful new method for monitoring the dynamics of cellular activity from small populations of cells.     

Fatigue crack growth analysis of different adhesive systems: Effects of mode mixity and load level

The aim of this paper is to investigate the fatigue fracture behavior of three different adhesive systems (epoxy‐based, acrylic, and a rubber‐like adhesive). To achieve this, double cantilever beam specimens were manufactured with different adhesives and tested under several mode mixities and different load levels. Fatigue crack growth rate was evaluated through a Paris law equation. For postprocessing, the compliance‐based beam method was used. Results showed that the variation of the threshold energy with load level is more pronounced for the epoxy‐based adhesive. The crack propagation life is higher for the acrylic adhesive. Although, for pure mode I conditions, the normalized threshold of the rubber‐like adhesive is lower, for pure mode II, it was higher than the epoxy‐based adhesive. Due to the normalization by the static fracture energy, the slope of the Paris law was approximately constant for all the adhesive systems.     

Photoprocesses in microaggregates

Despite the potential complexity of microaggregate-containing systems, photophysical probe techniques have made important fundamental contributions to our understanding of the structure and properties of the aggregates and of the dynamics and reactivity of small molecules added to the system. By appropriate choice of the probe and quencher, one can often reduce the behavior of such microheterogeneous systems to that of a simple pseudophase system, amenable to study by steady-state fluorescence techniques. Rather general photophysical probe-based methods are now available for measuring equilibrium constants for solute incorporation and exchange selectivity coefficients for counterion binding to various types of microaggregates, including micelles, vesicles, and reverse micelles.     

Efficacy of a national program to promote breast feeding: Chile 1993-2002

Promotion of breast feeding is a priority in Chilean health's policies. The aim of the study was to evaluate the tendency of breastfeeding (exclusive, continued, partial), in children less than 18 months old, controlled in the Chilean public health system, based in four national surveys. Through a 24 h food intake recall (breastfeeding, water, juice, infant formula, solids) food patterns were explored every 3 years, as well as maternal participation in jobs located away from home. the sample consisted of approximately 10 thousand children, less than 18 months old of the 28 health services throughout the country. The prevalence of children with exclusive breastfeeding, predominant (breastfeeding, water or juice), complemented (breastfeeding plus solids) or any other way of feeding for each month of age in each survey, and changes in period studied, was determined. Between 1993 and 2002, exclusive breastfeeding for 6 months increased from 16 to 43.1% (p<0.001) and predominant breastfeeding from 25.4 to 57.4%. at the same time, complemented breastfeeding at 12 months increased from 10.7 to 21.3%, and partial or complemented breastfeeding in 12 to 18 month old children went from 24.1 to 46.7%. Maternal work located away from home was inversely associated with the prevalence of exclusive and complemented breastfeeding during the first year (p<0.001). There has been a significant increase of maternal breastfeeding in the period analyzed. The negative effects of maternal labor on breastfeeding suggests to explore more effective forms of social support to the working mother.     

Recovery of phytosterols from sunflower oil deodorizer distillates

Phytosterols are usually recovered by crystallization from the deodorizer distillate (DD) of vegetable oils. In this work, the impact of the principal process variables (viz., solvents and cosolvents, cooling rate, crystallization temperature, and ripening time) on the quality and yield of the recovered phytosterols was studied by using a sunflower oil DD “enriched” (i.e., preconcentrated) via transesterification with ethanol (EDD) as a feedstock and commercial hexane as solvent (S), with S/EDD mass ratios of 3 to 5. Water (0 to 4.5 wt%) and ethanol (0 to 10 wt%) were used as cosovents, with crystallization temperatures between 0 and −20°C and crystallization times from 4 to 96 h. The cooling rate was either −20°C/h or “brisk chilling” from 40 to −5°C. The nature and composition of the EDD solvent and cosolvent composite arose as the most important process variable, strongly influencing both the percentage of sterol yield and the purity of the crystals, as well as their filterability and washability. Water-saturated hexane sufficed to give good crystallization, yet the beneficial effect of adding water as the single cosolvent was enhanced by adding small and precise amounts of ethanol. A recovery of sterols as high as 84% (with 36% purity) was achieved by using a single-stage batch crystallization of the S/EDD mixture (S/EDD=mass ratio 4).     

Photocatalytic reduction of CO<Subscript>2</Subscript> with H<Subscript>2</Subscript>O over modified TiO<Subscript>2</Subscript> nanofibers: Understanding the reduction pathway

Nanosized metal (Pt or Pd)-decorated TiO₂ nanofibers (NFs) were synthesized by a wet impregnation method. CdSe quantum dots (QDs) were then anchored onto the metal-decorated TiO₂ NFs. The photocatalytic performance of these catalysts was tested for activation and reduction of CO₂ under UV-B light. Gas chromatographic analysis indicated the formation of methanol, formic acid, and methyl formate as the primary products. In the absence of CdSe QDs, Pd-decorated TiO₂ NFs were found to exhibit enhanced performance compared to Pt-decorated TiO₂ NFs for methanol production. However, in the presence of CdSe, Pt-decorated TiO₂ NFs exhibited higher selectivity for methanol, typically producing ～90 ppmg^?1·h^?1 methanol. The CO₂ photoreduction mechanism is proposed to take place via a hydrogenation pathway from first principles calculations, which complement the experimental observations.

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Reliability analysis for electronic devices using beta‐Weibull distribution

Today, in reliability analysis, the most used distribution to describe the behavior of electronic products under voltage profiles is the Weibull distribution. Nevertheless, the Weibull distribution does not provide a good fit to lifetime datasets that exhibit bathtub‐shaped or upside‐down bathtub–shaped (unimodal) failure rates, which are often encountered in the reliability analysis of electronic devices. In this paper, a reliability model based on the beta‐Weibull distribution and the inverse power law is proposed. This new model provides a better approach to model the performance and fit of the lifetimes of electronic devices. To estimate the parameters of the proposed model, a Bayesian analysis is used. A case study based on the lifetime of a surface mounted electrolytic capacitor is presented, the results showed that the estimation of the proposed model differs from the inverse power law–Weibull and that it affects directly the mean time to failure, the failure rate, the behavior, and the performance of the capacitor under analysis.