A Single-Stage Water-Gas Shift Reaction over Highly Active and Stable Si- and Al-Substituted Pt/CeO2 Catalysts

Ce0.88Si0.1Pt0.02O2-d and Ce0.88Al0.1Pt0.02O2-d catalysts were synthesized by using a low-temperature sonochemical method and characterized by using XRD, TEM, XPS, FTIR, and BET surface analyzer. The catalytic activities of these compounds were investigated for the watergas shift reaction in the temperature range of 140-440 degrees C. The substitution of Si in Ce0.98Pt0.02O2-d increased the releasing capacity of lattice oxygen, whereas the substitution of Al decreased the reducibility of Ce0.98Pt0.02O2-d, as evidenced by hydrogen temperature-programmed reduction studies. However, both the catalysts showed a considerable improvement in terms of activity and stability compared to Ce0.98Pt0.02O2-d. The combined activity measurement and characterization results suggest that the increase in the oxygen vacancy, which acts as a dissociation center for water, is the primary reason for the improvement in the activity of modified Ce0.98Pt0.02O2-d. Both the catalysts are 100?% selective toward H2 production, and approximately 99?% conversion of CO to CO2 was observed at 260 and 270 degrees C for Ce0.88Si0.1Pt0.02O2-d and Ce0.88Al0.1Pt0.02O2-d, respectively. These catalysts do not deactivate during the daily startup/shutdown operations and are sustainable even after prolonged reaction. Notably, these catalysts do not require any pretreatment or activation during startup/shutdown operations.

Spatial Modulation and Space Shift Keying in Single Carrier Communication

Spatial modulation (SM) and space shift keying (SSK) are relatively new modulation techniques which are attractive in multi-antenna communications. Single carrier (SC) systems can avoid the peak-to-average power ratio (PAPR) problem encountered in multicarrier systems. In this paper, we study SM and SSK signaling in cyclic-prefixed SC (CPSC) systems on MIMO-ISI channels. We present a diversity analysis of MIMO-CPSC systems under SSK and SM signaling. Our analysis shows that the diversity order achieved by (n(t), n(r)) SSK scheme and (n(t), n(r), Theta(M)) SM scheme in MIMO-CPSC systems under maximum-likelihood (ML) detection is n(r), where n(t), n(r) denote the number of transmit and receive antennas and Theta(M) denotes the modulation alphabet of size M. Bit error rate (BER) simulation results validate this predicted diversity order. Simulation results also show that MIMO-CPSC with SM and SSK achieves much better performance than MIMO-OFDM with SM and SSK.

Low temperature CO oxidation and water gas shift reaction over Pt/Pd substituted in Fe/TiO2 catalysts

We demonstrate the activity of Ti0.84Pt0.01Fe0.15O2-delta and Ti0.73Pd0.02Fe0.25O2-delta catalysts towards the CO oxidation and water gas shift (VMS) reaction. Both the catalysts were synthesized in the nano crystalline form by a low temperature sonochemical method and characterized by different techniques such as XRD, FT-Raman, TEM, FT-IR, XPS and BET surface analyzer. H-2-TPR results corroborate the intimate contact between noble metal and Fe ions in the both catalysts that facilitates the reducibility of the support. In the absence of feed CO2 and H-2, nearly 100% conversion of CO to CO2 with 100% H-2 selectivity was observed at 300 degrees C and 260 degrees C respectively, for Ti0.84Pt0.01Fe0.15O2-delta and Ti0.73Pd0.02Fe0.25O2-delta catalyst. However, the catalytic performance of Ti0.73Pd0.02Fe0.25O2-delta deteriorates in the presence of feed CO2 and H-2. The change in the support reducibility is the primary reason for the significant increase in the activity for CO oxidation and WGS reaction. The effect of Fe addition was more significant in Ti0.73Pd0.02Fe0.25O2-delta than Ti0.84Pt0.01Fe0.15O2-delta. Based on the spectroscopic evidences and surface phenomena, a hybrid reaction scheme utilizing both surface hydroxyl groups and the lattice oxygen was hypothesized over these catalysts for WGS reaction. The mechanisms based on the formate and redox pathway were used to fit the ldnetic data. The analysis of experimental data shows the redox mechanism is the dominant pathway over these catalysts. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Field extension code based dispersion matrices for coherently detected space-time shift keying

Motivated by the recent Coherent Space-Time Shift Keying (CSTSK) philosophy, we construct new dispersion matrices for rotationally invariant PSK signaling sets. Given a specific PSK signal constellation, the dispersion matrices of the existing CSTSK scheme were chosen by maximizing the mutual information over randomly generated sets of dispersion matrices. In this contribution we propose a general method for constructing a set of structured dispersion matrices for arbitrary PSK signaling sets using Field Extension (FE) codes and then study the attainable Symbol Error Rate (SER) performance of some example constructions. We demonstrate that the proposed dispersion scheme is capable of outperforming the existing dispersion arrangement at medium to high SNRs.

Nanostructured Pd modified Ni/CeO2 catalyst for water gas shift and catalytic hydrogen combustion reaction

Nanostructured Pd-modified Ni/CeO2 catalyst was synthesized in a single step by solution combustion method and characterized by XRD, TEM, XPS, TPR and BET surface analyzer techniques. The catalytic performance of this compound was investigated by performing the water gas shift (WGS) and catalytic hydrogen combustion (CHC) reaction. The present compound is highly active and selective (100%) toward H-2 production for the WGS reaction. A lack of CO methanation activity is an important finding of present study and this is attributed to the ionic substitution of Pd and Ni species in CeO2. The creation of oxide vacancies due to ionic substitution of aliovalent ions induces dissociation of H2O that is responsible for the improved catalytic activity for WGS reaction. The combined H-2-TPR and XPS results show a synergism exists among Pd, Ni and ceria support. The redox reaction mechanism was used to correlate experimental data for the WGS reaction and a mechanism involving the interaction of adsorbed H-2 and O-2 through the hydroxyl species was proposed for CHC reaction. The parity plot shows a good correspondence between the experimental and predicted reaction rates. (c) 2012 Elsevier B.V. All rights reserved.

Automatic road extraction using high resolution satellite images based on Level Set and Mean Shift methods

Analysis of high resolution satellite images has been an important research topic for urban analysis. One of the important features of urban areas in urban analysis is the automatic road network extraction. Two approaches for road extraction based on Level Set and Mean Shift methods are proposed. From an original image it is difficult and computationally expensive to extract roads due to presences of other road-like features with straight edges. The image is preprocessed to improve the tolerance by reducing the noise (the buildings, parking lots, vegetation regions and other open spaces) and roads are first extracted as elongated regions, nonlinear noise segments are removed using a median filter (based on the fact that road networks constitute large number of small linear structures). Then road extraction is performed using Level Set and Mean Shift method. Finally the accuracy for the road extracted images is evaluated based on quality measures. The 1m resolution IKONOS data has been used for the experiment.

Structured Dispersion Matrices From Division Algebra Codes for Space-Time Shift Keying

We propose a novel method of constructing Dispersion Matrices (DM) for Coherent Space-Time Shift Keying (CSTSK) relying on arbitrary PSK signal sets by exploiting codes from division algebras. We show that classic codes from Cyclic Division Algebras (CDA) may be interpreted as DMs conceived for PSK signal sets. Hence various benefits of CDA codes such as their ability to achieve full diversity are inherited by CSTSK. We demonstrate that the proposed CDA based DMs are capable of achieving a lower symbol error ratio than the existing DMs generated using the capacity as their optimization objective function for both perfect and imperfect channel estimation.

Synthesis of nanosized Ce0.85M0.1Ru0.05O2-delta (M = Si, Fe) solid solution exhibiting high CO oxidation and water gas shift activity

Nanosized Ce0.85M0.1Ru0.05O2-delta (M = Si, Fe) has been synthesized using a low temperature sonication method and characterized using XRD, TEM, XPS and H-2-TPR. The potential application of both the solid solutions has been explored as exhaust catalysts by performing CO oxidation. The addition of Si- and Fe-in Ce0.95Ru0.05O2-delta greatly enhanced the reducibility of Ce0.85M0.1Ru0.05O2-delta (M = Si, Fe), as indicated by the H-2-TPR study. The oxygen storage capacity has been used to correlate surface oxygen reactivity to the CO oxidation activity. Both the compounds reversibly release lattice oxygen and exhibit excellent CO oxidation activity with 99% conversion below 200 degrees C. A bifunctional reaction mechanism involving CO oxidation by the extraction of lattice oxygen and rejuvenation of oxide vacancy with gas feed O-2 has been used to correlate experimental data. The performance of both the solid solutions has also been investigated for energy application by performing the water gas shift reaction. The present catalysts are highly active and selective towards the hydrogen production and a lack of methanation activity is an important finding of present study.

Microstructure and texture evolution during sub-transus thermo-mechanical processing of Ti-6Al-4V-0.1B alloy: part II. static annealing in (alpha plus beta) regime

The first part of this study describes the evolution of microstructure and texture in Ti-6Al-4V-0.1B alloy during sub-transus rolling vis-A -vis the control alloy Ti-6Al-4V. In the second part, the static annealing response of the two alloys at self-same conditions is compared and the principal micromechanisms are analyzed. Faster globularization kinetics has been observed in the Ti-6Al-4V-0.1B alloy for equivalent annealing conditions. This is primarily attributed to the alpha colonies, which leads to easy boundary splitting via multiple slip activation in this alloy. The other mechanisms facilitating lamellar to equiaxed morphological transformations, e.g., termination migration and cylinderization, also start early in the boron-modified alloy due to small alpha colony size, small aspect ratio of the alpha lamellae, and the presence of TiB particles in the microstructure. Both the alloys exhibit weakening of basal fiber (ND||aOE (c) 0001 >) and strengthening of prism fiber (RD||aOE (c) aOE(a)) upon annealing. A close proximity between the orientations of fully globularized primary alpha and secondary alpha phases during alpha -> beta -> alpha transformation has accounted for such a texture modification.

On the zeta function of a periodic-finite-type shift

Periodic-finite-type shifts (PFT's) are sofic shifts which forbid the appearance of finitely many pre-specified words in a periodic manner. The class of PFT's strictly includes the class of shifts of finite type (SFT's). The zeta function of a PET is a generating function for the number of periodic sequences in the shift. For a general sofic shift, there exists a formula, attributed to Manning and Bowen, which computes the zeta function of the shift from certain auxiliary graphs constructed from a presentation of the shift. In this paper, we derive an interesting alternative formula computable from certain ``word-based graphs'' constructed from the periodically-forbidden word description of the PET. The advantages of our formula over the Manning-Bowen formula are discussed.

Dynamics of the Indian-Ocean oxygen minimum zones

In the Indian Ocean, mid-depth oxygen minimum zones (OMZs) occur in the Arabian Sea and the Bay of Bengal. The lower part of the Arabian-Sea OMZ (ASOMZ; below 400 m) intensifies northward across the basin; in contrast, its upper part (above 400 m) is located in the central/eastern basin, well east of the most productive regions along the western boundary. The Bay-of-Bengal OMZ (BBOMZ), although strong, is weaker than the ASOMZ. To investigate the processes that maintain the Indian-Ocean OMZs, we obtain a suite of solutions to a coupled biological/physical model. Its physical component is a variable-density, 6 1/2-layer model, in which each layer corresponds to a distinct dynamical regime or water-mass type. Its biological component has six compartments: nutrients, phytoplankton, zooplankton, two size classes of detritus, and oxygen. Because the model grid is non-eddy resolving (0.5 degrees), the biological model also includes a parameterization of enhanced mixing based on the eddy kinetic energy derived from satellite observations. To explore further the impact of local processes on OMZs, we also obtain analytic solutions to a one-dimensional, simplified version of the biological model. Our control run is able to simulate basic features of the oxygen, nutrient, and phytoplankton fields throughout the Indian Ocean. The model OMZs result from a balance, or lack thereof, between a sink of oxygen by remineralization and subsurface oxygen sources due primarily to northward spreading of oxygenated water from the Southern Hemisphere, with a contribution from Persian-Gulf water in the northern Arabian Sea. The northward intensification of the lower ASOMZ results mostly from horizontal mixing since advection is weak in its depth range. The eastward shift of the upper ASOMZ is due primarily to enhanced advection and vertical eddy mixing in the western Arabian Sea, which spread oxygenated waters both horizontally and vertically. Advection carries small detritus from the western boundary into the central/eastern Arabian Sea, where it provides an additional source of remineralization that drives the ASOMZ to suboxic levels. The model BBOMZ is weaker than the ASOMZ because the Bay lacks a remote source of detritus from the western boundary. Although detritus has a prominent annual cycle, the model OMZs do not because there is not enough time for significant remineralization to occur.

Solution nuclear magnetic resonance structure of the GATase subunit and structural Basis of the interaction between GATase and ATPPase subunits in a two-subunit-type GMPS from methanocaldococcus jannaschii

The solution structure of the monomeric glutamine amidotransferase (GATase) subunit of the Methanocaldococcus janaschii (Mj) guanosine monophosphate synthetase (GMPS) has been determined using high-resolution nuclear magnetic resonance methods. Gel filtration chromatography and N-15 backbone relaxation studies have shown that the Mj GATase subunit is present in solution as a 21 kDa (188-residue) monomer. The ensemble of 20 lowest-energy structures showed root-mean-square deviations of 0.35 +/- 0.06 angstrom for backbone atoms and 0.8 +/- 0.06 angstrom for all heavy atoms. Furthermore, 99.4% of the backbone dihedral angles are present in the allowed region of the Ramachandran map, indicating the stereochemical quality of the structure. The core of the tertiary structure of the GATase is composed of a seven-stranded mixed beta-sheet that is fenced by five alpha-helices. The Mj GATase is similar in structure to the Pyrococcus horikoshi (Ph) GATase subunit. Nuclear magnetic resonance (NMR) chemical shift perturbations and changes in line width were monitored to identify residues on GATase that were responsible for interaction with magnesium and the ATPPase subunit, respectively. These interaction studies showed that a common surface exists for the metal ion binding as well as for the protein-protein interaction. The dissociation constant for the GATase-Mg2+ interaction has been found to be similar to 1 mM, which implies that interaction is very weak and falls in the fast chemical exchange regime. The GATase-ATPPase interaction, on the other hand, falls in the intermediate chemical exchange regime on the NMR time scale. The implication of this interaction in terms of the regulation of the GATase activity of holo GMPS is discussed.

Flow-enhanced pairing and other unusual effects in Fermi gases in synthetic gauge fields

Recent experiments on fermions in synthetic gauge fields result in systems with a spin-orbit coupling along one spatial axis, a detuning field, and a Zeeman field. We show theoretically that the presence of all three results in interesting and unusual phenomena in a system of interacting fermions (interactions described by a scattering length). For two fermions, bound states appear only over a certain range of the center-of-mass momenta. The deepest bound state appears at a nonzero center-of-mass momentum. For center-of-mass momenta without a bound state, the gauge field induces a resonance-like feature in the scattering continuum resulting in a large scattering phase shift. In the case of many particles, we demonstrate that the system, in a parameter range, shows flow-enhanced pairing, i.e., a Fulde-Farrell-Larkin-Ovchnnikov superfluid state made of robust pairs with a finite center-of-mass momentum. Yet another regime of parameters offers the opportunity to study strongly interacting normal states of spin-orbit-coupled fermionic systems utilizing the resonance-like feature induced by the synthetic gauge field.

Dynamics of a flexible splitter plate in the wake of a circular cylinder

Rigid splitter plates in the wake of bluff bodies are known to suppress the primary vortex shedding. In the present work, we experimentally study the problem of a flexible splitter plate in the wake of a circular cylinder. In this case, the splitter plate is free to continuously deform along its length due to the fluid forces acting on it; the flexural rigidity (EI) of the plate being an important parameter. Direct visualizations of the splitter plate motions, for very low values of flexural rigidity (EI), indicate periodic traveling wave type deformations of the splitter plate with maximum tip amplitudes of the order of I cylinder diameter. As the Reynolds number based on cylinder diameter is varied, two regimes of periodic splitter plate motions are found that are referred to as mode I and mode II, with a regime of aperiodic motions between them. The frequency of plate motions in both periodic modes is found to be close to the plane cylinder Strouhal number of about 0.2, while the average frequencies in the non-periodic regime are substantially lower. The measured normalized phase speed of the traveling wave for both periodic modes is also close to the convection speed of vortices in the plane cylinder wake. As the flexural rigidity of the plate (EI) is increased, the response of the plate was found to shift to the right when plotted with flow speed or Re. To better capture the effect of varying EI, we define and use a non-dimensional bending stiffness, K*, similar to the ones used in the flag flutter problem, K*=EI/(0.5 rho(UL3)-L-2), where U is the free-stream velocity and L is the splitter plate length. Amplitude data for different EI cases when plotted against this parameter appear to collapse on to a single curve for a given splitter plate length. Measurements of the splitter plate motions for varying splitter plate lengths indicate that plates that are substantially larger than the formation length of the plane cylinder wake have similar responses, while shorter plates show significant differences.

Asynchronous Measurement of Transient Phase-Shift Resulting From RF Receiver State-Change

In a wireless receiver, a down-converted RF signal undergoes a transient phase shift, when the gain state is changed to adjust for varying conditions in transmission and propagation. A method is developed, in which such phase shifts are detected asynchronously, and their undesirable effects on the bit error rate are corrected. The method was developed for and used in, the system-level characterization and calibration of a 65-nm CMOS UHF receiver. The phase-shifts associated with specific gain-state transitions were measured within a test framework, and used in the baseband signal processing blocks to compensate for errors, whenever the receiver anticipated a gain-state transition.