Novel modulation strategy for a CLC resonant dual active bridge

This paper proposes a novel modulation strategy for a phase controlled Capacitor-Inductor-Capacitor (CLC) Resonant Dual Active Bridge (RDAB). The proposed modulation strategy improves the soft turn-on, Zero-Current-Switching (ZCS) and Zero-Voltage-Switching (ZVS) range of the converter while only minimally increasing the required reactive currents in the ac link. A mathematical analysis of the proposed modulation scheme is presented along with a theoretical loss comparison between several modulation strategies. The proposed modulation strategy was implemented and the experimental results are presented.

Dual Drug Delivery Microcapsules via Layer-by-Layer Self-Assembly

The integration of hydrophobic and hydrophilic drugs in the polymer microcapsule offers the possibility of developing a new drug delivery system that combines the best features of these two distinct classes of material. Recently, we have reported the encapsulation of an uncharged water-insoluble drug in the polymer membrane. The hydrophobic drug is deposited using a layer-by-layer (LbL) technique, which is based on the sequential adsorption of oppositely charged polyelectrolytes onto a charged substrate. In this paper, we report the encapsulation of two different drugs, which are invariably different in structure and in their solubility in water. We have characterized these dual drug vehicular capsules by confocal laser scanning microscopy, atomic force microscopy, visible microscopy, and transmission electron microscopy. The growth of a thin film on a flat substrate by LbL was monitored by UV−vis spectra. The desorption kinetics of two drugs from the thin film was modeled by a second-order rate model.

Catalyst effectiveness factor for redox model kinetic equation

A generalized isothermal effectiveness factor correlation has been proposed for catalytic reactions whose intrinsic kinetics are based on the redox model. In this correlation which is exact for asymptotic values of the Thiele parameter the effect of the parameters appearing in the model, the order of the reaction and particle geometry are incorporated in a modified form of Thiele parameter. The relationship takes the usual form: Image and predicts effectiveness factor with an error of less than 2% in a range of Thiele parameter that accommodates both the kinetic and diffusion control regimes.

(v, k, λ) Configurations and self-dual codes

The incidence matrix of a (v, k, λ) configuration is used to construct a (2v, v) and a (2v + 2, v + 1) self-dual code. If the incidence matrix is a circulant, the codes obtained are quasi-cyclic and extended quasi-cyclic, respectively. The weight distributions of some codes of this type are obtained.

Homogeneous hydrogenations ofα, β-unsaturated compounds using pentacyanocobaltate (II) anion as catalyst system

Hydrogenation of someα, β-unsaturated carbonyl compounds using potassium pentacyanocobaltate (II), K3Co(CN)5, as a homogeneous catalyst has been investigated. Thus, hydrogenation of 1-carvone (I), mesityl oxide (4), 2-cyclohexenone (8) and benzalacetone (6) afforded the corresponding dihydrocompounds. Hydrogenation ofβ-ionone (10) afforded a mixture of theα, β-dihydrocompounds (14) and (15). In all these cases, it was observed that the reaction proceeded to completion only in the presence of added base. Hydrogenation of 5α-androst-l-en-17β-ol-3-one acetate (19) afforded the saturated compound, 5α-androst-17β-ol-3-one (20) in 60% yield. It was found that other steroid enones and dienones were not reduced by this catalyst system.

Harmonic response of a shock mount employing dual-phase damping

In this note, the application of dual-phase damping to a simple shock mount experiencing a harmonic input is described. The damping ratio is a function of the relative displacement between the foundation and the mounted mass. The purpose of employing such a damping is to reduce the absolute transmissibility over the whole frequency range.

Vapor phase oxidation of ethanol over thorium molybdate catalyst

Ethanol oxidation in the vapor phase was studied in an isothermal flow reactor using thorium molybdate catalyst in the temperature range 220–280 °C. Under these conditions the catalyst was highly selective to acetaldehyde formation. The rate data were well represented by a steady state two-stage redox model given by the equation: View the MathML source The parameters of the above model were estimated by linear and nonlinear least squares methods. In the case of nonlinear estimation the sum of the squares of residuals decreased. The activation energies and preexponential factors for the reduction and oxidation steps of the model, estimated by nonlinear least squares technique are: 9.47 kcal/mole, 9.31 g mole/ (sec) (g cat) (atm) and 9.85 kcal/mole, 0.17 g mole/(sec) (g cat) (atm)0.5, respectively. Oxidations of ethanol and methanol over thorium molybdate catalyst were compared under similar conditions.

Carbon-Supported Pt-TiO2 as a Methanol-Tolerant Oxygen-Reduction Catalyst for DMFCs

Carbon-supported Pt-TiO2 (Pt-TiO2/C) catalysts with varying at. wt ratios of Pt to Ti, namely, 1:1, 2:1, and 3:1, are prepared by the sol-gel method. The electrocatalytic activity of the catalysts toward oxygen reduction reaction (ORR), both in the presence and absence of methanol, is evaluated for application in direct methanol fuel cells (DMFCs). The optimum at. wt ratio of Pt to Ti in Pt-TiO2/C is established by fuel cell polarization, linear sweep voltammetry, and cyclic voltammetry studies. Pt-TiO2/C heattreated at 750 degrees C with Pt and Ti in an at. wt ratio of 2:1 shows enhanced methanol tolerance, while maintaining high catalytic activity toward ORR. The DMFC with a Pt-TiO2/C cathode catalyst exhibits an enhanced peak power density of 180 mW/cm(2) in contrast to the 80 mW/cm(2) achieved from the DMFC with carbon-supported Pt catalyst while operating under identical conditions. Complementary data on the influence of TiO2 on the crystallinity of Pt, surface morphology, and particle size, surface oxidation states of individual constituents, and bulk and surface compositions are also obtained by powder X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive analysis by X-ray, and inductively coupled plasm optical emission spectrometry.

Origin of activation of Lattice Oxygen and Synergistic Interaction in Bimetal-Ionic Ce0.89Fe0.1Pd0.01O2-delta Catalyst

Flourite-type nanocrystalline Ce0.9Fe0.1O2-delta and Ce0.89Fe0.1Pd0.01O2-delta solid solutions have been synthesized by solution combustion method,'.which show higher oxygen storage/release property (OSC) compared to CeO2 and Ce0.8Zr0.2O2. Temperature programmed reduction an XPS study reveal that the presence of Pd ion in Ce0.9Fe0.1O2-delta facilitates complete reduction of Fe3+ to Fe2+ state and partial reduction of Ce4+ to Ce3+ state at.temperatures as low as 105 degrees C compared to 400 degrees C for monometal-ionic Ce0.9Fe0.1O2-delta. Fe3+ ion is reduced to Fe2+ and not to Feo due to favorable redox potential for Ce4+ + Fe2+ -> Ce3+ + Fe3+ reaction. Using first-principles density functional theory calculation we determine M-O (M = Pd, Fe, Ce) bond lengths, and find that bond lengths vary from shorter (2.16 angstrom) to longer (2.9 angstrom) bond distances compared to mean Ce-O bond distance of 2.34 angstrom. for CeO2. Using these results in bond valence analysis, we show that oxygen with bond valences as low as -1.55 are created, leading to activation of lattice oxygen in the bimetal ionic catalyst. Temperatures of CO oxidation and NO reduction by CO/H-2 are lower with the bimetalionic Ce0.89Fe0.1Pd0.01O2-delta catalyst compared to monometal-ionic Ce0.9Fe0.1O2-delta and Ce0.99Pd0.01O2-delta catalysts. From XPS studies of Pd impregnated on CeO2 and Fe2O3 oxides, we show that the synergism leading to low temperature activation of lattice oxygen in bimetal-ionic catalyst Ce0.89Fe0.1Pd0.01O2-delta is due to low-temperature reduction of Pd2+ to Pd-0, followed by Pd-0 + 2Fe(3+) -> Pd2+ + 2Fe(2+), Pd-0 + 2Ce(4+) -> Pd2+ + 2Ce(3+) redox reaction.

Microstrip square ring antenna for dual-band operation

This paper presents a generalized approach to design an electromagnetically coupled microstrip ring antenna for dual-band operation. By widening two opposite sides of a square ring antenna, its fractional bandwidth at the primary resonance mode can be increased significantly so that it may be used for practical applications. By attaching a stub to the inner edge of the side opposite to the feed arm, some of the losses in electrical length caused by widening can be regained. More importantly, this addition also alters the current distribution on the antenna and directs radiations at the second resonant frequency towards boresight. It has also been observed that for the dual frequency configurations studied, the ratio of the resonant frequencies (center dot r(2)center dot center dot r(1)) can range between 1.55 and 2.01. This shows flexibility in designing dual frequency antennas with a desired pair of resonant frequencies.

EIT as a tool to observe dual wavelength operation of a semiconductor laser

We propose a simplified technique for dual wavelength operation of an extended cavity semiconductor laser, and its characterization using electromagnetically induced transparency (EIT). In this laser cavity scheme light beam is made converging before it incidences on the cavity grating. The converging angle of the beam creates two longitudinal oscillating modes of resonating cavity. Frequency separation between the longitudinal modes are measured with the help of beat frequency generation in a photodiode and creating pair of EIT spectra in Rb vapor. The pair of EIT dips that are generated due to dual wavelength of this laser (that is used as control laser) can be used to estimate frequency difference between the generated wavelengths. Width of EIT spectra can be used to estimate line width of individual wavelength components.

Dual yolk-shell structure of carbon and silica-coated silicon for high-performance lithium-ion batteries

Silicon batteries have attracted much attention in recent years due to their high theoretical capacity, although a rapid capacity fade is normally observed, attributed mainly to volume expansion during lithiation. Here, we report for the first time successful synthesis of Si/void/SiO2/void/C nanostructures. The synthesis strategy only involves selective etching of SiO2 in Si/SiO2/C structures with hydrofluoric acid solution. Compared with reported results, such novel structures include a hard SiO2-coated layer, a conductive carbon-coated layer, and two internal void spaces. In the structures, the carbon can enhance conductivity, the SiO2 layer has mechanically strong qualities, and the two internal void spaces can confine and accommodate volume expansion of silicon during lithiation. Therefore, these specially designed dual yolk-shell structures exhibit a stable and high capacity of 956 mA h g−1 after 430 cycles with capacity retention of 83%, while the capacity of Si/C core-shell structures rapidly decreases in the first ten cycles under the same experimental conditions. The novel dual yolk-shell structures developed for Si can also be extended to other battery materials that undergo large volume changes.

Ce0.67Cr0.33O2.11: A New Low-Temperature O-2 Evolution Material and H-2 Generation Catalyst by Thermochemical Splitting of Water

Ce0.67Cr0.33O2.11 was synthesized by hydrothermal method using diethylenetriamine as complexing agent (Chem. Mater. 2008, 20, 7268). Ce0.67Cr0.33O2.11 being the only compound likes UO2+delta to have excess oxygen, it releases a large proportion of its lattice oxygen (0.167 M [O]/mole of compound) at relatively low temperature (465 degrees C) directly and it has been utilized for generation of H-2 by thermo-splitting of water. An almost stoichiometric amount of H-2 (0.152 M/Mole of compound) is generated at much lower temperature (65 degrees C). There is an almost comparable amount of oxygen release and hydrogen generation over this material at very low temperature comparedto other CeO2-MOx (Mn, Fe, Cu, and Ni) mixed-oxide solid solutions (O-2 evolution >= 1300 degrees C and H-2 generation at 1000 degrees C). The reversible nature of oxygen release and intake of this material is attributed to its fluorite Structure and coupling between the Ce4+/Ce3+ and Cr4+/6+/Cr3+ redox couples. Compound shows reversible oxygen release and intake by H2O absorption and subsequent hydrogen release to gain parent structure and hence this material can be utilized for generation of H-2 at very low temperature by thermo-chemical splitting of water.

A Methanol-Tolerant Carbon-Supported Pt-Au Alloy Cathode Catalyst for Direct Methanol Fuel Cells and Its Evaluation by DFT

A Pt-Au alloy catalyst of varying compositions is prepared by codeposition of Pt and Au nanoparticles onto a carbon support to evaluate its electrocatalytic activity toward an oxygen reduction reaction (ORR) with methanol tolerance in direct methanol fuel cells. The optimum atomic weight ratio of Pt to Au in the carbon-supported Pt-Au alloy (Pt-Au/C) as established by cell polarization, linear-sweep voltammetry (LSV), and cyclic voltammetry (CV) studies is determined to be 2:1. A direct methanol fuel cell (DMFC) comprising a carbon-supported Pt-Au (2:1) alloy as the cathode catalyst delivers a peak power density of 120 mW/cm2 at 70 °C in contrast to the peak power density value of 80 mW/cm2 delivered by the DMFC with carbon-supported Pt catalyst operating under identical conditions. Density functional theory (DFT) calculations on a small model cluster reflect electron transfer from Pt to Au within the alloy to be responsible for the synergistic promotion of the oxygen-reduction reaction on a Pt-Au electrode.