Sorbent injection into a slipstream baghouse for mercury control: Project summary

A project led by the Energy and Environmental Research Center to test and demonstrate sorbent injection as a cost-effective mercury control technology for utilities burning lignites has shown effective mercury capture under a range of operating conditions. Screening, parametric, and long-term tests were carried out at a slipstream facility representing an electrostatic precipitator–activated carbon injection–fabric filter configuration (called a TOXECON™ in the United States). Screening tests of sorbent injection evaluated nine different sorbents, including both treated and standard activated carbon, to compare mercury capture as a function of sorbent injection rate. Parametric tests evaluated several variables including air-to-cloth (A/C) ratio, flue gas temperature, cleaning frequency, and dust loading to determine the effect on mercury control and systems operation. Long-term tests (approximately 2 months in duration) evaluated the sustainability of systems operation.     

Fabrication of Thin-Film SrCe0.9Eu0.1O3−δ Hydrogen Separation Membranes on Ni–SrCeO3 Porous Tubular Supports

SrCe_0.9Eu_0.1O_3−δ thin-film (∼30 μm) tubular hydrogen separation membranes were developed in order to obtain high hydrogen fluxes. Fifteen centimeters long, one end closed, NiO–SrCeO₃ tubular supports were fabricated by tape casting, followed by rolling the green tape on a circular rod. SrCe_0.9Eu_0.1O_3−δ powders were prepared by the citrate process and coated on partially sintered NiO–SrCeO₃ tubular supports. Leakage-free hydrogen membrane cells were obtained by adjusting the presintering and final sintering temperatures to reduce the difference of linear shrinkage rates between SrCe_0.9Eu_0.1O_3−δ thin films and NiO–SrCeO₃ supports. A hydrogen flux of 2.2 cm³/min was obtained for the SrCe_0.9Eu_0.1O_3−δ on Ni–SrCeO₃ tubular hydrogen separation membranes at 900°C using 25% H₂ balanced with Ar and 3% H₂O as the feed gas and He as the sweep gas. Thus, a 40% single pass yield of pure H₂ was achieved with this membrane.     

Carbon nanotube biogels

There are numerous biomedical devices that rely on efficient electrical communication with living tissue. Advancement of these devices depends on effectively bridging the tissue/electrode interface and is dependent on advances in new materials. We report on the modification of carbon nanotubes with various biomolecules to develop biological based conducting material suitable for bridging this interface. The non-covalent modification of single-wall carbon nanotubes (SWCNT) with three biological molecules (DNA, hyaluronic acid and chitosan) has been achieved. Coherent SWCNT biofilms were produced from the dispersions by drop casting onto glassy carbon electrodes. The SWCNT biofilms underwent hydration upon immersion into electrolyte to form a gel that exhibited considerably lower impedance than the glassy carbon substrate. In addition, incorporation of the neurotrophin NT-3 into these CNT biogels was possible with the controlled release of the NT-3 being influenced by the application of electrical stimulation. Compatibility of the materials prepared with a fibroblast cell line (L-929) was also tested and it was determined that they were non-toxic to the cells under consideration. The soft character of these conducting biogels coupled with their dynamic nature provides an extra dimension in designing interfaces between the hard, digital electronics world and the soft, amorphous world of biological systems.     

Optimized observation of tungsten tracers for investigation of formation of porous anodic alumina

Improved methods are presented for investigating the flow of anodic alumina during the formation of porous anodic films on aluminium in phosphoric acid. In particular, the use of tungsten nanolayer tracers with increased flatness is shown to result in enhanced definition of the influences of flow on the tracer distribution, as observed by electron microscopy. Additionally, taper sectioning of films, by ultramicrotomy, and parallel sectioning of films, by sputtering using an Ar⁺ ion plasma, enable tungsten distributions across cells to be determined. In the case of an Al–3.5 at.%W alloy, the flow results in an inner alumina layer lining the pore walls that is relatively free of tungsten species and an outer cell layer of comparatively high tungsten content. Both sectioning procedures also show the presence of fine cell boundary bands of relatively high tungsten content, which are suggested to result from the transport of tungsten, enriched in the alloy immediately beneath the film, toward the cell boundary by the alloy/film interface.     

A lithographic approach to determine volume expansion factors during anodization: Using the example of initiation and growth of TiO2-nanotubes

The present work investigates the formation of nanotubes by anodizing titanium at 20 V in glycerol containing either 0.175 M or 0.35 M NH₄F. A photoresist-masking method of thin Ti films allows to use SEM cross-sections to directly obtain information on oxide morphology, layer thickness and metal substrate loss. Therefore not only features of the initial growth stages but also oxide expansion factors can accurately be determined. The expansion factors were found to be 2.4 for the initial formation of a barrier layer, 1.7–1.9 during pore initiation and 2.7–3.1 as the main nanotubes develop. These values (>2.6) suggest substantial contribution to steady state tube growth by a plastic oxide flow mechanism. Combined with RBS efficiency measurements the method presented here allows facile and direct investigation of the mechanism of pore/tube formation.     

X-ray diffraction studies of electrochemical graphite intercalation compounds of ionic liquids

Electrochemical intercalation studies are used to characterize a series of ionic liquids composed of a variety of cationic and anionic species. Electrochemically, the ionic liquids are characterized by cyclic voltammograms and charge–discharge experiments for the intercalation and de-intercalation of the various cationic and anionic species into graphite. X-ray structure analysis is also performed to determine the relationship between the electrochemical behaviour of the ionic liquids, and the formation of intercalated graphitic compounds. Two different types of imidazolium cations are studied, specifically the di- and trisubstituted imidazolium. These cations are paired with the following anions: tetrafluoroborate, hexafluorophosphate, bis(trifluoromethanesulfonyl)imide, bis(perfluoroethanesulfonyl)imide, nitrate and hydrogen sulfate. Results indicate stronger intercalation chemistry for the trisubstituted imidazoliums, correlating with the greater charge–discharge efficiencies found for these types of ionic liquids. Many of the anions exhibit very poor charge–discharge efficiencies, correlating to very poorly formed graphite intercalates. The exception to this is the hydrogen sulfate intercalate, which had low charge–discharge efficiencies but formed a well defined graphite intercalate. Only the imide based anions exhibited both high charge–discharge efficiencies and the formation of a clearly defined graphite intercalate.     

An experimental and computational study of the aerodynamic and passive ventilation characteristics of small livestock trailers

This paper presents a combined experimental and computational study of the aerodynamics and passive ventilation characteristics of small livestock trailers within which the majority of animals in the United Kingdom are transported to market. Data obtained from a series of wind tunnel experiments using a 1/7th scale model of a simplified towing vehicle and trailer are compared with complementary computational fluid dynamics (CFD) analyses, based on steady-state RANS turbulence modelling, of the coupled external/internal flow field. Good agreement between the two is obtained everywhere except at the rear of the trailer. Since the internal flow field and overall ventilation rates contribute to animal welfare, CFD is used to generate detailed internal flow fields and air residence times for use within an overall welfare assessment. The results demonstrate that the flow fields in the upper and lower decks differ significantly and that ventilation rates are much larger and air residence times much smaller on the upper deck.     

Hamilton-Jacobi skeleton on cortical surfaces

In this paper, we propose a new method to construct graphical representations of cortical folding patterns by computing skeletons on triangulated cortical surfaces. In our approach, a cortical surface is first partitioned into sulcal and gyral regions via the solution of a variational problem using graph cuts, which can guarantee global optimality. After that, we extend the method of Hamilton-Jacobi skeleton to subsets of triangulated surfaces, together with a geometrically intuitive pruning process that can trade off between skeleton complexity and the completeness of representing folding patterns. Compared with previous work that uses skeletons of 3-D volumes to represent sulcal patterns, the skeletons on cortical surfaces can be easily decomposed into branches and provide a simpler way to construct graphical representations of cortical morphometry. In our experiments, we demonstrate our method on two different cortical surface models, its ability of capturing major sulcal patterns and its application to compute skeletons of gyral regions.     

Comparison of Uniaxial Wafer Bending and Contact-Etch-Stop-Liner Stress Induced Performance Enhancement on Double-Gate FinFETs

Longitudinal piezoresistance (pi) coefficients for n- and p-type double-gate (DG) FinFETs with sidewall channels along (110) surface and (110) channel direction are measured via wafer-bending experiments (51.4 and -37 X 10 ^-11 Pa^-1 for n- and p-FinFETs, respectively) and are found to differ from bulk Si (110) (31.2 and -71.8 X 10 ^-11 Pa^-1 for n- and p-Si, respectively). Compressive and tensile contact-etch-stop liners (CESLs) are fabricated on DG FinFETs and are found to induce higher channel stress than in planar MOSFETs, with 30% enhancement in the saturation current for the shortest channel-length devices in both n- and p-MOSFETs, whereas the long devices show little or no enhancement. The channel-length dependence of the enhancement suggests that stress coupling into the FinFET channels from the CESL occurs via the fin extensions and not through the gate.     

Simulation Models for Investigation of Multiuser Scheduling in MIMO Broadcast Channels

Spatial correlation is a result of insufficient antenna spacing among multiple antenna elements, while temporal correlation is caused by Doppler spread. This paper compares the effect of spatial and temporal correlation in order to investigate the performance of multiuser scheduling algorithms in multiple‐input multiple‐output (MIMO) broadcast channels. This comparison includes the effect on the ergodic capacity, on fairness among users, and on the sum‐rate capacity of a multiuser scheduling algorithm utilizing statistical channel state information in spatio‐temporally correlated MIMO broadcast channels. Numerical results demonstrate that temporal correlation is more meaningful than spatial correlation in view of the multiuser scheduling algorithm in MIMO broadcast channels. Indeed, the multiuser scheduling algorithm can reduce the effect of the Doppler spread if it exploits the information of temporal correlation appropriately. However, the effect of spatial correlation can be minimized if the antenna spacing is sufficient in rich scattering MIMO channels regardless of the multiuser scheduling algorithm used.