An integrated process for biomass pyrolysis oil upgrading: A synergistic approach

Biomass pyrolysis is a promising path toward renewable liquid fuels. However, the calorific value of the pyrolysis oil (PO), also known as bio-oil, is low due to the high content of organic oxygenates and water. The oxygen content of PO can be reduced by hydrodeoxygenation, in which hydrogen is used to remove oxygen. An economic disadvantage of hydrodeoxygenation pathway is its dependence on hydrogen as an expensive feedstock. An alternative technology is to upgrade PO in hot, high pressure water, known as hydrothermal processing. The present paper studies upgrading pyrolysis oil derived from Norwegian spruce by (1) hydrodeoxygenation in a liquid hydrocarbon solvent using nanodispersed sulphide catalysts and (2) hydrothermal treatment in near-supercritical water. Experimental results and simulation studies suggested that if water soluble products are reformed for hydrogen production, the hydrodeoxygenation pathway would be a net consumer of hydrogen, whilst the hydrothermal pathway could produce a significant hydrogen excess. By comparison, the fuel yield from hydrodeoxygenation was significantly higher than hydrothermally treated fuel. Therefore, in the present study, an integrated model was proposed which demonstrates that the synergistic integration of hydrothermal and hydrodeoxygenation upgrading technologies can yield an optimal configuration which maximises fuel production, whilst obviating the need to purchase hydrogen. In this optimal configuration, 32% of raw pyrolysis-oil is hydrothermally treated and the rest is sent for hydrodeoxygenation. The results of a techno-economic analysis suggests that if the proposed integrated approach is used, it is possible to produce biofuel (43% gasoline, and 57% diesel) at a very competitive minimum selling price of 428 $m−3 (1.62$/gallon)

Observations of TeV gamma rays from Markarian 501 at large zenith angles

TeV gamma rays from the blazar Markarian 501 have been detected with the University of Durham Mark 6 atmospheric Cerenkov telescope using the imaging technique at large zenith angles. Observations were made at zenith angles in the range 70 - 73 deg during 1997 July and August when Markarian 501 was undergoing a prolonged and strong flare.Comment: 7 pages, 2 figures, accepted for publication in J. Phys. G.: Nucl. Part. Phy

Fabrication of Fully Isolated nFETs Using Oxidized Porous Silicon

SOl (Silicon on Insulator) technology is an option in improving device performance as smaller devices run into scaling challenges. The devices for this study were fabricated using a FIPOS (Fully Isolated Porous Oxidized Silicon) process, which results in localized SOl active regions. The oxidation of electrochemically etched porous silicon (PSi) has demonstrated success in the formation of device quality localized S01 for CMOS applications 11,21. The formation of PSi can be done selectively by controlling the Fermi level in areas to be etched or not etched, which is typically done by adjusting the level of doping Ill. An alternative method is to introduce a reversible donor species such as protons 121 or fluorine (this work) for the selective formation of islands of crystalline silicon surrounded by porous silicon. Implanted fluorine in silicon has demonstrated a donor effect upon annealing at low temperature (600°C), which is reversible as the fluorine outdiffuses during higher temperature annealing (1000°C). This technique has been used to form crystalline silicon active regions with thickness less than 200 nm completely surrounded by oxidized porous silicon 131, shown in figure 1. This study involves the fabrication and characterization of nFETs on the active areas to investigate the electronic integrity of the silicon device regions

Quantum Molecular Dynamics Approach to the Nuclear Matter Below the Saturation Density

Quantum molecular dynamics is applied to study the ground state properties of nuclear matter at subsaturation densities. Clustering effects are observed as to soften the equation of state at these densities. The structure of nuclear matter at subsaturation density shows some exotic shapes with variation of the density.Comment: 21 pages of Latex (revtex), 9 Postscript figure

The challenge of modelling nitrogen management at the field scale : simulation and sensitivity analysis of N2O fluxes across nine experimental sites using DailyDayCent

Peer reviewedPublisher PD

Thermoelastic Damping in Micro- and Nano-Mechanical Systems

The importance of thermoelastic damping as a fundamental dissipation mechanism for small-scale mechanical resonators is evaluated in light of recent efforts to design high-Q micrometer- and nanometer-scale electro-mechanical systems (MEMS and NEMS). The equations of linear thermoelasticity are used to give a simple derivation for thermoelastic damping of small flexural vibrations in thin beams. It is shown that Zener's well-known approximation by a Lorentzian with a single thermal relaxation time slightly deviates from the exact expression.Comment: 10 pages. Submitted to Phys. Rev.

VHE Gamma Rays from PKS 2155-304

The close X-ray selected BL Lac PKS 2155-304 has been observed using the University of Durham Mark 6 very high energy (VHE) gamma ray telescope during 1996 September/October/November and 1997 October/November. VHE gamma rays with energy > 300 GeV were detected from this object with a time-averaged integral flux of (4.2 +/- 0.7 (stat) +/- 2.0 (sys)) x 10^(-11) per cm2 per s. There is evidence for VHE gamma ray emission during our observations in 1996 September and 1997 October/November, with the strongest emission being detected in 1997 November, when the object was producing the largest flux ever recorded in high-energy X-rays and was detected in > 100 MeV gamma-rays. The VHE and X-ray fluxes show evidence of a correlation.Comment: 14 pages, 6 figures, accepted for publication in Ap.

Proposed method for searches of gravitational waves from PKS 2155-304 and other blazar flares

We propose to search for gravitational waves from PKS 2155-304 as well as other blazars. PKS 2155-304 emitted a long duration energetic flare in July 2006, with total isotropic equivalent energy released in TeV gamma rays of approximately $10^{45}$ ergs. Any possible gravitational wave signals associated with this outburst should be seen by gravitational wave detectors at the same time as the electromagnetic signal. During this flare, the two LIGO interferometers at Hanford and the GEO detector were in operation and collecting data. For this search we will use the data from multiple gravitational wave detectors. The method we use for this purpose is a coherent network analysis algorithm and is called {\tt RIDGE}. To estimate the sensitivity of the search, we perform numerical simulations. The sensitivity to estimated gravitational wave energy at the source is about $2.5 \times 10^{55}$ ergs for a detection probability of 20%. For this search, an end-to-end analysis pipeline has been developed, which takes into account the motion of the source across the sky.Comment: 10 pages, 7 figures. Contribution to 12th Gravitational Wave Data Analysis Workshop. Submitted to Classical and Quantum Gravity. Changes in response to referee comment

Separating N2O production and consumption in intact agricultural soil cores at different moisture contents and depths

Agricultural soils are a major source of the potent greenhouse gas and ozone depleting substance, N2O. To implement management practices that minimise microbial N2O production and maximise its consumption (i.e. complete denitrification) we must understand the interplay between simultaneously occurring biological and physical processes, especially how this changes with soil depth. Meaningfully disentangling these processes is challenging and typical N2O flux measurement techniques provide little insight into subsurface mechanisms. Additionally, denitrification studies are often conducted on sieved soil in altered O2 environments which relate poorly to in situ field conditions. Here, we use a novel dual headspace system with field-relevant O2 concentrations to incubate intact sandy clay loam textured agricultural topsoil (0-10 cm) and subsoil (50-60 cm) cores for 3-4 d at 50 and 70% water filled pore space (WFPS), respectively. 15N-N2O pool dilution and an SF6 tracer were used to determine the relative diffusivity (Ds/D0) and the net N2O emission and gross N2O emission and consumption rates. The relationship between calculated fluxes from the below- and above- soil core headspaces confirmed that the system performed well. We found no difference in Ds/D0 between soil depth fractions, which was probably because of the preservation of preferential flow pathways in intact cores. Both gross N2O emissions and uptake were not different with depth but were higher in the 50% WFPS, contrary to expectation. We attribute this to aerobic denitrification and simultaneously occurring denitrification and nitrification for the gross consumption and emission of N2O, respectively. Here, we developed a novel system that allows careful control of conditions and, with a headspace below and above a soil core, a more realistic reconstruction of in situ gas dynamics. We provide further evidence of substantial N2O consumption in drier soil and without net negative N2O emissions. The results from this study are important for the future application of the 15N-N2O pool dilution method and N budgeting and modelling, as required for improving management to minimise N2O losses