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In this work we estimate the yield of the radioisotope 225 A c in a thorium metal target geometry similar to that described by Roberston et al.. We do so in three different yet complimentary studies. In the first study, we pose a three-way coupled time-dependent model describing beam position, temperature field, and local growth of the activity of the radioisotope and solve this numerically. In the second study, we present an analytical solution of the model equations for a generalized solid target in the "beam-thin" limit, i.e. where only a small fraction of the incoming energy of the proton beam is deposited into the thorium material. In the third study, we use the insight gained from the analytical solution and describe an operating strategy to maximize yield by modulating the beam flux temporally. [ABSTRACT FROM AUTHOR]

Increased natural gas production in recent years has spurred intense interest in methane (CH4) emissions associated with its production, gathering, processing, transmission and distribution. Gathering and processing facilities (G&P facilities) are unique in that the wide range of gas sources (shale, coal-bed, tight gas, conventional, etc.) results in a wide range of gas compositions, which in turn requires an array of technologies to prepare the gas for pipeline transmission and distribution. We present an overview and detailed description of the measurement method and analysis approach used during a 20-week field campaign studying CH4 emissions from the natural gas G&P facilities between October 2013 and April 2014. Dual tracer flux measurements and onsite observations were used to address the magnitude and origins of CH4 emissions from these facilities. The use of a second tracer as an internal standard revealed plume-specific uncertainties in the measured emission rates of 20-47 %, depending upon plume classification. Combining downwind methane, ethane (C2H6), carbon monoxide (CO), carbon dioxide (CO2), and tracer gas measurements with onsite tracer gas release allows for quantification of facility emissions, and in some cases a more detailed picture of source locations. [ABSTRACT FROM AUTHOR]

In this work, we present a methodology to characterise the axial dispersion of a solute during steady-flow through a compressible bed of wood chips under mechanical load. We use a non-invasive imaging technique, namely electrical resistance tomography (ERT), to visualise the uniaxial displacement of a salt solution. Here we demonstrate that under two limiting cases the porosity of the porous bed varies slowly in the flow-direction and to the lowest order can be considered a constant. This simplified the optimisation routine we used to match the experimental data to the numerical results of the advection-diffusion equation. Using this, a methodology to estimate the axial dispersion is given by a minimisation scheme. In the experimental portion of the work we measure the axial dispersion of a bed of hemlock wood chips at three different kappa numbers κ, and compacted to three different compaction pressures pc. We find that the dispersion De in the axial direction varies as a function of the porosity ε, according to $D_{{\rm e}} = a\varepsilon {}^{b} $, where a = 7.2 × 10−4 m2/s and b = −3.8 for hemlock wood chips. © 2011 Canadian Society for Chemical Engineering [ABSTRACT FROM AUTHOR]

In this work, we present a methodology to characterise the permeability of a compressible bed of wood chips under mechanical load. We show that under the limiting condition of when the mechanical compression is large in comparison to hydraulic pressure the equations of motion can be linearised and solved to produce an expression approximating the variation in porosity along the length of the bed. We show how this may be used, in conjunction with multiple linear regression to estimate permeability of the bed. In the experimental portion of the work we measure the permeability of a bed of hemlock wood chips at three different kappa numbers κ, and compacted to three different mechanical loads, i.e. compaction pressures pc. The usefulness of these estimates was then tested by predicting the pressure drop versus flow relationship for conditions outside the range of the linearised solution; the equations of motion were solved numerically with knowledge of the measured permeability. Good agreement was obtained. After accounting for compressibility effects, we find that our correlation has lower flow resistances than the literature correlations. © 2011 Canadian Society for Chemical Engineering [ABSTRACT FROM AUTHOR]