Kernel based partially linear models and nonlinear identification

In this note, we propose partially linear models with least squares support vector machines (LS-SVMs) for nonlinear ARX models. We illustrate how full black-box models can be improved when prior information about model structure is available. A real-life example, based on the Silverbox benchmark data, shows significant improvements in the generalization ability of the structured model with respect to the full black-box model, reflected also by a reduction in the effective number of parameters.     

DSP implementation of output voltage reconstruction in CSI-basedconverters

Current-source-inverter-based uninterruptible power supplies and V/f-controlled induction motor drives require sensing of two or more load voltages in addition to the DC voltage sensors used for protection purposes. This paper proposes a digital-signal-processor (DSP)-based load voltage control scheme that requires only information provided by the DC-bus voltage sensor. Load voltage estimation is based on AC line voltage reconstruction by means of a recursive least-square error algorithm that uses the information available on the DC bus and knowledge of the pulsewidth modulation gating pattern. Thus, the system minimizes the transducer count and, therefore, enhances reliability and ruggedness. Experimental results show that the load voltage can be reconstructed and its RMS value controlled for a wide range of operating conditions with errors of at most 4%. Moreover, the use of the space-vector modulation technique ensures a reduced load voltage harmonic distortion, which remains within the 5% range at nominal voltage and for all load conditions. The paper presents the DSP algorithms required for the operation of the system and key experimental results obtained on a three-phase 208-V 60-Hz 2-kVA prototype unit     

Effect of MWNTs concentration and cooling rate on the morphological,structural, and electrical properties of non‐isothermally crystallized PEN/MWNT nanocomposites

The effect of multiwall carbon nanotubes (MWNT) concentration and cooling rate on the morphological, structural and electrical properties of non‐isothermally crystallized Poly(ethylene naphthalate) nanocomposites (PEN/MWNT) was studied. PEN/MWNT nanocomposites containing 1 and 2 wt % of nanotubes were prepared by melt blending in a mini twin screw extruder. Nanocomposite samples with different degree of crystallinity (X_c) were obtained via non‐isothermally crystallization at cooling rates of 2, 10, 20, and 300°C min^?1. In this study it was demonstrated that carbon nanotubes and cooling rate strongly influence morphological and structural characteristics of PEN. Calorimetric results showed that the peak crystallization temperature (T_c) of PEN nanocomposites was increased ～9° through heterogeneous nucleation with respect to pure PEN. X‐ray diffraction revealed that carbon nanotubes modify the crystalline structure of PEN favoring the formation of β‐crystals, and this effect increases with the nanotubes content. On the basis of X‐ray scattering analysis, the variation of lamellar thickness revealed that nanotubes promote the formation of lamellar crystals with average thickness of 20 nm at different cooling rates. These structural and morphological changes play an important role on the electrical properties of nanocomposites. It was found that higher concentration of nanotubes and crystallinity promotes electrical conductivity of nanocomposites in the order of semiconductors (until 1 × 10^?4 S cm^?1) as well as permittivity of 20 at different tested frequencies. This may due to the interconnected networks of nanotubes throughout the crystalline structure formed in PEN nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41765.     

Perceptions of the school social context across the transition to middle school: Heightened sensitivity among Latino students?

The current study was designed to examine the ways in which perceived behavioral norms among grade mates and school social climate vary across the transition to middle school. The main goals of the study were to test whether Latino students may be more sensitive to the school social climate than White students and whether perceived behavioral norms might help explain this association. Cross-sectional analyses comparing Latino and White students (N = 383) revealed that perceptions of school social climate and behavioral norms became more negative across the middle school transition. Multiple regression analysis showed that school climate perceptions predicted self-reported academic compliance and rule breaking only for Latino students. Mediational analysis revealed that the association between perceived climate and self-reported rule breaking was partially accounted for by perceptions of behavioral norms for rule breaking only among Latino students. Taken together, the results suggest that compared with White students, Latino students are more sensitive to school social climate as it relates to their school conduct. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Ant tunneling—a granular media perspective

Laboratory and field data show that the digging habits of ants and the resulting nest architecture vary with soil conditions, yet, the geomechanical understanding of ant tunneling is lacking. We study the excavation strategies used by harvester ants in clay, silt, sand, and gravel at water contents that range from dry to saturated. The study focuses on the conditions at the tunnel face that determine particle removal methods, digging rate, the development of branches, and tunneling patterns. Analytical and numerical models provide particle-level insight into the experimental observations and help identify the causal links that relate ants digging performance and nest geometric patterns with the properties of the granular medium such as grain size, moisture, and packing density. Results highlight ants’ exceptional ability to sense the prevailing geomechanical conditions in tunnels, and to adapt excavation strategies, transport methods and tunneling patterns to those conditions, within their inherent size and strength limitations. The resulting tunnel structure emerges as a mechanically-convenient and energy-efficient topology based on local information gather by ants along the tunnel and at the tunnel face.     

Synthesis and optical behavior of PLED devices based on (PMMA)/(PAA)/Er(AP)6Cl3 complex and N,N′-didodecyl-3,4,9,10-perylene tetracarboxylic diimide composites

The realization of efficient polymeric light emitting diode (PLEDs) in a double-layered configuration was investigated. The devices are composed by transparent conductive oxide (ITO)/MoO₃/organic layers/aluminum/selenium, conformed by thin film sandwich structures obtained by vacuum evaporation. Two organic layers were developed. First a n-type organic layer of composite based on polymethylmethacrylate (PMMA)/polyacrilic acid (PAA)/Er(AP)₆Cl₃ complex and second a n-type organic semiconductor, N,N′-didodecyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C₁₂H₂₅). The rare earth complex composites and the perilenic compound were synthesized and characterized using UV–Visible absorption, XPS, and NMR techniques, respectively. Driving voltage of devices was lowered by applying MoO₃ thin film as buffer layer and high current intensity efficiency was obtained applying a perilenic film. The effect of MoO₃ and PTCDI-C₁₂H₂₅ thin films, on the optical and the physical properties of the electroluminescent devices were discussed. I–V measurements have shown that the structures exhibit diode characteristics and the electroluminescent signal increases when PTCDI-C₁₂H₂₅ thin layer is introduced between the anode and the holes transporting layer. The morphology of the thin films with and without buffer layer indicates that introduction of this layer allows to obtain a homogeneous surface morphology. The results indicate that carrier injection ability and optimized charge balance is obtained to the lowest driving voltage and highest intensities efficiency among the referenced devices.     

Design of a Modular UPQC Configuration Integrating a Components Economical Analysis

A design procedure to select the components in a modular unified power-quality conditioner configuration based on single-phase cells is presented. The procedure is based on the fact that the load and distributor operating conditions range are known and it is required to impose stiff operating conditions in both the load side (regulation) and the point of common coupling side (power factor). Due to the arbitrary number of cells to be used in a modular approach, the proposed design procedure allows to select the power semiconductors and capacitors based on an economical evaluation, so an optimal number of cells can be chosen to minimize the overall power cell cost. This design procedure is well suited for modular configurations, where several degrees of freedom are not covered if just technical criteria are followed. Thus, an economic approach can be used to select the appropriate components. The rest of the devices, i.e., the transformers turn ratio and passive filters, are chosen using classical design methods based on technical issues such that the power cells operate within its permissible ratings. A practical case evaluation is presented for a medium voltage system application.     

Resonance tracking atomic force acoustic microscopy quantitative modulus mapping of carbon nanotubes‐reinforced acrylonitrile–butadiene–styrene polymer

This work presents a resonance tracking atomic force acoustic microscopy (RT‐AFAM) quantitative modulus mapping of carbon nanotubes‐reinforced acrylonitrile–butadiene–styrene polymer. RT‐AFAM average local modulus values registered were in good agreement with those measured by nanoindentation test. RT‐AFAM mapping modulus, nanoindentation, and transmission electron microscopy imaging showed that carbon nanotubes reinforcement of acrylonitrile–butadiene–styrene polymer matrix gives an elastic modulus enhancement of approximately 18.3% compared with the polymer matrix alone and showed that this technique provides high spatial resolution and helps to characterize the elastic properties of reinforced thermoplastic polymers and new compound materials at nanoscale. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40628.