Influence of Drying Conditions on Amine-Functionalized SBA-15 as Adsorbent of CO2

Adsorption of pure CO₂ on amine-functionalized SBA-15 mesoporous silica materials has been studied. Adsorbent materials were prepared by grafting the silica surface with aminopropyl (AP), ethylene-diamine (ED) and diethylene-triamine (DT) organosilane molecules. Materials so obtained were dried under air atmosphere at 110 °C and at room temperature. CO₂ adsorption isotherms were carried out at 45 °C, showing that grafted materials are very efficient for CO₂ removal at atmospheric pressure when samples are dried at 20 º C. However, when the drying step is carried out at 110 °C in air, CO₂ adsorption capacity is low. DRIFTS analysis has shown that amino groups can undergo oxidation to oxime or imine species during drying. Adsorption capacity of the materials was found to be unchanged after some consecutive adsorption?Cdesorption cycles, being the regeneration step performed at 110 °C under vacuum.     

Petri nets‐based model for the analysis of NORIA protocol

Network rOle‐based Routing Intelligent Algorithm is a novel routing algorithm for wireless sensor networks, which combine various effective techniques in order to reduce energy consumption and improve data routes. This algorithm uses role assignment for distributing tasks over the network nodes and fuzzy logic for making decisions. There is a clear need for the use of formal methods to validate the correctness of the protocols as well as performance and functionality prior to the deployment of such algorithms in a real environment. This paper presents a formal and rigorous study of Network rOle‐based Routing Intelligent Algorithm. Prioritised‐timed coloured petri nets (PTCPNs) have been chosen as an appropriate modelling language. In this way, PTCPNs have been used to describe complete and unambiguous specifications of system behaviour, whereas CPNTools is used to evaluate the correctness of the protocol using state space exploration and for performance evaluation using simulation. Copyright © 2015 John Wiley & Sons, Ltd.     

Potential use of visible and near infrared reflectance spectroscopy for the estimation of nitrogen fractions in forages harvested from permanent meadows

One‐hundred and ninety‐two herbage samples from permanent meadows located in the mountains of León (NW Spain) were analyzed for total nitrogen (total N), nitrogen in trichloroacetic acid precipitated matter (TCAN), borate–phosphate buffer insoluble nitrogen (BPBN), neutral‐detergent insoluble nitrogen (NDIN) and acid‐detergent insoluble nitrogen (ADIN). These data were used to calculate the partition of nitrogen fractions proposed by the Cornell Net Carbohydrate and Protein System (CNCPS): A (total N ? TCAN), B₁ (TCAN ? BPBN), B₂ (BPBN ? NDIN), B₃ (NDIN ? ADIN) and C (ADIN). Near‐infrared reflectance spectroscopy (NIRS) technology accurately predicted total N, TCAN and NDIN, as judged by coefficient of determination (R²) and ratio performance deviation (RPD) values greater than 0.90 and 2.5, respectively. The rest of the insoluble N fractions (BPBN and ADIN) were predicted with less accuracy by NIRS. Estimations of CNCPS N fractions (A, B₁, B₂, B₃ and C) using visible–NIR spectra of forage samples did not allow accurate predictions (R² < 0.90; RPD < 2.5). Copyright © 2005 Society of Chemical Industry     

Room temperature performance of low threshold 1.34-1.44-/spl mu/m GaInNAs-GaAs quantum-well lasers grown by molecular beam epitaxy

Room temperature lasing emission at 1.338 and 1.435 /spl mu/m with threshold current densities of 1518 and 1755 A/cm/sup 2/, respectively, is obtained in broad area GaInNAs-GaAs laser diodes (LDs) grown by molecular beam epitaxy. The 1.338-/spl mu/m LDs show a power output per facet up to 0.20 W/A, a characteristic temperature (T/sub 0/) of 78 K, and an external transparency current density (J/sub tr/) of 0.77 kA/cm/sup 2/. Increasing the lasing wavelength to 1.435 /spl mu/m results in a larger J/sub tr/ of 1.16 kA/cm/sup 2/ and a lower T/sub 0/ of 62 K, due to larger nonradiative recombination. However, the 1.435-/spl mu/m LDs still display a power output per facet up to 0.15 W/A, and a high internal quantum efficiency of 52%. These improved performances are achieved without the need to use strain compensation layers, Sb as a surfactant during the quantum-well growth, or a postgrowth thermal anneal cycle.     

Design Strategy to Optimize the Reliability of Grid-Connected PV Systems

This paper presents a strategy, based on the design-of-experiments technique, aimed at optimizing the reliability in inverters for photovoltaic systems. The process involves designing the inverter several times, each time with different specifications, and calculating the reliability for each design. The specifications are established in a systematic manner, in such a way that the parameters with the highest impact are easily identified. The optimization procedure follows a standard reliability estimation methodology and involves modifying the stress factors in a judicious manner. The strategy is exemplified with an integrated boost inverter and a desired mean time between failures of 12 years.     

A default hierarchy for pronouncing English

The authors study the principles governing the power and efficiency of the default hierarchy, a system of knowledge acquisition and representation. The default hierarchy trains automatically, yet yields a set of rules which can be easily assessed and analyzed. Rules are organized in a hierarchical structure containing general (default) and specific rules. In training the hierarchy, general rules are learned before specific rules. In using the hierarchy, specific rules are accessed first, with default rules used when no specific rules apply. The main results concern the properties of the default hierarchy architecture, as revealed by its application to English pronunciation. Evaluating the hierarchy as a pronouncer of English, the authors find that its rules capture several key features of English spelling. The default hierarchy pronounces English better than the neural network NETtalk, and almost as well as expert-devised systems     

Electrical conductivity of polyethylene-carbon-fibre composites mixed with carbon black

The study of electrical conductivity of high-density polyethylene-carbon-fibre composites mixed with different concentrations of carbon black is reported. The influence of the mixing procedure of the additives and material preparation is examined with regard to the conductivity values. The use of these two filler types in polyethylene composites combines the conducting features of both. Thus, while fibres provide charge transport over large distances (several millimetres), carbon black particles improve the interfibre contacts. Results are discussed with reference to simple electrical models. It is shown that for composites in which the segregated carbon black-polyethylene component lies above the percolation threshold the electrical interfibre contacts are activated through carbon black particle bridges, leading to a conductivity rise. This effect is more relevant in the case of shorter fibres. Processing of the material involving fibre orientation, such as in injection-moulding, decreases drastically the conductivity level reached.     

Ruptured fission yeast walls. Structural discontinuities related to the cell cycle

Distributions of rupture sites of fission yeast cells ruptured by glass beads have been related to a new morphometric analysis. As shown previously (Johnson et al., Cell Biophysics, 1995), ruptures were not randomly distributed nor was their distribution dictated by geometry, rather, ruptures at the extensile end were related to cell length just as the rate of extension is related to cell length. The extension patterns of early log, mid-log, late log, and stationary phase cells from suspension cultures were found to approximate the linear growth patterns of Kubitschek and Clay (1986). The median length of cells was found to decline through the log phase in an unbalanced manner.     

Nanosized Nb-TiO/sub 2/ gas sensors derived from alkoxides hydrolization

Nanocrystalline TiO/sub 2/ modified with Nb has been produced through the sol-gel technique. Nanopowders have been obtained by means of the hydrolysis of pure alkoxides with deionized water and peptization of the resulting hydrolysate with diluted acid nitric at 100/spl deg/C. The addition of Nb stabilizes the anatase phase to higher temperatures. XRD spectra of the undoped and the Nb-doped samples show that the undoped sample has been almost totally converted to rutile at 600/spl deg/C, meanwhile the doped samples present still a low percentage of rutile phase. Nanocrystalline powders stabilized at 600/spl deg/C with grain sizes of about 17 nm have successfully been synthesized by the addition of Nb with a concentration of 2% at., which appears to be an adequate additive concentration to improve the gas sensor performances, such as it is suggested by the catalytic conversion efficiency experiments performed from FTIR measurements. FTIR absorbance spectra show that catalytic conversion of CO occurs at lower temperatures when niobium is introduced. The electrical response of the films to different concentrations of CO and ethanol has been monitored in dry and wet environments in order to test the influence of humidity in the sensor response. The addition of Nb decreases the working temperature and increases the stability of the layers. Also, large enhancement of the response time is obtained even with lower working temperatures. Moreover, humidity effects on the gas sensor response toward CO and ethanol are less important in Nb-doped samples than in the undoped ones.     

pn Junction applications and transport properties in polysilicon rods

B-Doped polysilicon rods have been studied through their crystalline structure and electronic transport properties. P Diffusion data and the properties of the p-n junctions obtained are also discussed. Avalanche current distribution and reverse bias electric field spikes have been carefully studied.It is concluded that this material is quite suitable for low-cost solar cell applications, and, from preliminary experiments, could be of interest for power transient suppressors.