Estimating the Attraction Domain for the Boost Inverter

This work presents an approach for estimating the domain of attraction for polynomial systems with state and control‐signal constraints, including saturation. In many problems, it is possible to derive global stability properties for such systems, neglecting constraints. Consideration of the constraints usually makes the problem much more complicated. In this paper, the stability analysis performed for the unconstrained case is used for the problem as a whole. For application of the method, there are powerful computational tools that can be employed in cases of polynomial systems. The technique is not only valid for the analysis of equilibrium points, but also for other attractors, such as limit cycles. As examples, the domain of attraction for given control laws is estimated for both a nonlinear DC‐DC boost converter and for a boost inverter.     

Boosting the photocatalytic hydrogen production of TiO2 by using copper hexacyanocobaltate as co-catalyst

The development of cheap and efficient co-catalysts is crucial to improve the performance of well-known photocatalysts towards the hydrogen evolution reaction. Here, copper hexacyanocobaltate was evaluated for the first time as a potential candidate to be used as co-catalyst coupled with conventional TiO₂. Copper hexacyanocobaltate was formed by chemical precipitation in the presence of TiO₂, without needing further treatments. The composite exhibited paramount performance towards hydrogen generation, surpassing by up to 16 times the behavior reached with bare TiO₂. This composite also overcome the performance of conventional TiO₂ modified with copper and cobalt oxides derived from copper hexacyanocobaltate. The enhanced behavior of TiO₂/Cu₃[Co(CN)₆]₂ composite was promoted by the efficient separation of photogenerated charge carries, and the faster charge transfer from photocatalyst towards species in solution, as it was proved by the photoelectrochemical characterization of the materials. Furthermore, the composite experienced a slight detriment (15%) in its hydrogen production rate after four consecutive photocatalyst tests. This variation was attributed to the slow leaching of copper in the co-catalyst caused by its partial transformation into metal hydroxides, as it was suggested by the ex-situ XPS characterization. Nevertheless, the structural characterization evinced the presence of the Cu₃[Co(CN)₆]₂ in the composite after long-term use. This study should be considered a proof of concept on a reliable route to obtain appropriate composites for hydrogen production using light as primary energy source.     

Liquid crystal crown ether derived from cyclic tetramer of epichlorohydrin

Summary A liquid crystal crown ether is obtained by chemical modification of the cyclic tetramer derived from epichlorohydrin with sodium 4-cyano-4′-biphenoxide. The crown ether exhibits a nematic mesophase and a high glass transition temperature.     

Specific and generalized expectancies in marital interaction.

40 married couples engaged in 2 laboratory interactions. The Marital Agendas Protocol was used to assess relational efficacy, and spouses' expectancies for partner behaviors during each interaction were elicited. Subsequent to the interactions, spouses' perceptions of their partners' actual behaviors were indicated, and spouses chose situational or dispositional attributions for each behavior. Results showed that distressed couples expect more negative and fewer positive behaviors and that spouses with high relational efficacy choose relationship-enhancing attributions more often than do low-efficacy spouses. The low-efficacy group showed strong preferences for distress-maintaining attributions. The results are interpreted as supporting the concept of sentiment override as well as the usefulness of the specific operationalization of relational efficacy utilized. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mesure automatique des paramétres de bruit des MESFET hyperfréquences

An automatic noise parameter measurement test set is described in two sections : (i) A novel noise parameter extraction procedure from a set of noise figure measurements is developped. The experimental minimum noise figure is no longer required and the sensitivity to measurement incertainties is found to be very low. (ii) An automatic input tuner with a large number of precalibrated and reproducible positions is designed and realized. The last part give examples of broadband (8 to 17 GHz) noise parameters characterization ofmmic GaAsmesfets when both the automatic tuner and the extraction procedure are used.     

Near-Infrared Lasing in Four-Zigzag Edged Nanographenes by 1D versus 2D Electronic π-Conjugation

The search of compounds emitting in the near-infrared (NIR) has been accelerated owing to their use in biomedical and telecommunications applications. In this regard, nanographenes (NGs) are attractive materials adequate for integration with other technologies, which have recently demonstrated amplified spontaneous emission (ASE) and lasing across the visible spectrum. Here, the optical and ASE properties of four-zigzag edged NGs of the [m,n]peri-acenoacene family are reported, whose size is increased through conjugation extension by varying n (from 3 to 5) while keeping m = 2. Results show that such 1D conjugation extension method is more efficient in terms of shifting the photoluminescence (PL) to the infrared (PL at 710 nm in the larger compound, PP-Ar) than through 2D conjugation extension as in previously reported NGs (PL at 676 nm with the largest compound FZ3, with n = 3 and m = 4). Additionally, PP-Ar shows dual-ASE (at 726 and 787 nm), whose origin is elucidated through Raman and transient absorption spectroscopies. These compounds’ potential for red and NIR lasing is demonstrated through the fabrication of distributed feedback lasers with top-layer resonators. This study paves the way towards the development of stable low-cost all-plastic NIR lasers.     

Reduced-gate convolutional long short-term memory using predictive coding for spatiotemporal prediction

Spatiotemporal sequence prediction is an important problem in deep learning. We study next-frame(s) video prediction using a deep-learning-based predictive coding framework that uses convolutional LSTM (convLSTM) modules. We introduce a novel rgcLSTM architecture that requires a significantly lower parameter budget than a comparable convLSTM. By using a single multifunction gate, our reduced-gate model achieves equal or better next-frame(s) prediction accuracy than the original convolutional LSTM while using a smaller parameter budget, thereby reducing training time and memory requirements. We tested our reduced gate modules within a predictive coding architecture on the moving MNIST and KITTI datasets. We found that our reduced-gate model has a significant reduction of approximately 40% of the total number of training parameters and a 25% reduction in elapsed training time in comparison with the standard convolutional LSTM model. The performance accuracy of the new model was also improved. This makes our model more attractive for hardware implementation, especially on small devices. We also explored a space of 20 different gated architectures to get insight into how our rgcLSTM fits into that space.     

Three‐time scale singular perturbation control and stability analysis for an autonomous helicopter on a platform

A three‐time scale singular perturbation control law is designed for a nonlinear helicopter model in vertical flight. The proposed control law is based on time scale decomposition and is able to achieve the desired altitude by selecting a desired angular velocity and the associated collective pitch angle of the blades. The stability of the system is performed by presenting a stability analysis for generic three‐time scale singularly perturbed systems, which allows to construct a composite Lyapunov function for the resultant closed‐loop system by using time scale separation and also providing mathematical expressions for the upper bounds of the singularly perturbed parameters that define the three‐time scale. Numerical results on both, the singular perturbation control strategy and the stability analysis, are also presented for the studied nonlinear highly coupled helicopter model. Copyright © 2012 John Wiley & Sons, Ltd.     

Using the scanning electron microprobe and secondary ion mass spectrometry to locate 14C- and 13C-labelled plant residues within soil aggregates

Increasing concentrations of CO2 in the atmosphere are placing emphasis on the necessity for sequestering carbon (C) into soil organic matter (SOM). By studying the interior parts of soil aggregates, a better understanding of the incorporation and sequestration of plant residue materials within these aggregates could be obtained. The location of newly added plant residues within soil aggregates may also assist in the investigation of the impact of these newly added plant materials on soil aggregation. This study investigated two different techniques for determining the location of newly added plant residues within soil aggregates by using plant materials labelled with 14C and 13C isotopes incorporated into two different soil types, Black Earth (Pellic Vertisol) and Red Clay (Chromic Vertisol). Both autoradiography combined with scanning electron microprobe analysis (14C) and secondary ion mass spectrometry (SIMS) (13C) were successfully used for detecting the presence and location of the newly added plant residues fragments within soil aggregates of both soil types. The use of labelled plant materials is essential for the study of the location of newly added plant materials within soil aggregates, and this has proven to be a useful tool for studying the impact of residue additions on soil aggregate formation. Furthermore, these methods have been shown to be useful for determining the incorporation and sequestration of C materials within soil aggregates. The development of the 13C SIMS technique could alleviate the necessity for the use of the radioactive isotope 14C in soil studies.