Nonmedical applications of a positron camera

Hawkesworth, M.R.; Parker, D.J.; Fowles, P.; Crilly, J.F.; Jefferies, N. L.; Jonkers, G.

doi:10.1016/0168-9002(91)91073-5

Cited by 67 publications

(32 citation statements)

References 6 publications

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“…Here we summarize the principal functional principle with emphasis on geoscientific applications. Other non-medical applications Hawkesworth and Parker, 1995;Hawkesworth et al, 1991;Parker et al, 1993Parker et al, , 1994Parker et al, , 2002Stein et al, 1997) address similar issues.…”

Section: Geopet: Applications Of Pet In Geosciencesmentioning

confidence: 98%

Geoscientific process monitoring with positron emission tomography (GeoPET)

et al. 2016

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Abstract. Transport processes in geomaterials can be observed with input-output experiments, which yield no direct information on the impact of heterogeneities, or they can be assessed by model simulations based on structural imaging using µ-CT. Positron emission tomography (PET) provides an alternative experimental observation method which directly and quantitatively yields the spatio-temporal distribution of tracer concentration. Process observation with PET benefits from its extremely high sensitivity together with a resolution that is acceptable in relation to standard drill core sizes. We strongly recommend applying high-resolution PET scanners in order to achieve a resolution on the order of 1 mm.We discuss the particularities of PET applications in geoscientific experiments (GeoPET), which essentially are due to high material density. Although PET is rather insensitive to matrix effects, mass attenuation and Compton scattering have to be corrected thoroughly in order to derive quantitative values.Examples of process monitoring of advection and diffusion processes with GeoPET illustrate the procedure and the experimental conditions, as well as the benefits and limits of the method.

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Section: Geopet: Applications Of Pet In Geosciencesmentioning

confidence: 98%

Geoscientific process monitoring with positron emission tomography (GeoPET)

et al. 2016

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“…During a PEPT experiment, there is usually a large number of coincidence events recorded. Of these events, a significant number (the majority) are actually corrupt (Hawkesworth et al, 1991). The corrupt events may result from either random or scattered pairing of the emitted γ rays.…”

Section: The Detection Processmentioning

confidence: 99%

“…This camera was designed for the application PET to engineering studies. Descriptions of the camera can be found in Hawkesworth, et al (1991) and Parker et al (1993Parker et al ( , 1994. The camera consists of a pair of multi-wired proportional chambers, operated in coincidence.…”

Section: Initial Cameramentioning

confidence: 99%

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Characterising porosity of multi-component mixtures in rotary mills

Sichalwe¹,

Govender²,

Mainza³

2011

Minerals Engineering

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“…The accuracy of PEPT also decreases as the speed of the particles increases due to the speed at which the camera can collect data (Hawkesworth et al, 1991). The use of tracers that are representative of the bulk powder is also a variable that needs to be addressed as segregation can occur and impact on the results obtained in the PEPT.…”

Section: Techniques Of Studying Powder Flowmentioning

confidence: 99%

Powder flow in vertical high shear mixer granulators

Tran¹

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An integral component in understanding the fundamental mechanisms of granulation is the powder flow behaviour within mixer granulators. All three classes of granulation rate processes: wetting and nucleation, consolidation and coalescence, and attrition and breakage require detailed knowledge of flow fields in mixing systems to enable rational approaches to the prediction of granule attributes. The three objectives of this thesis are to 1) develop a powder flow regime map to characterise the powder flow field, 2) investigate the effect of impeller speed, powder cohesion and blade-rake angle on powder flow and mixing behaviour and, 3) outline a framework for compartment models of vertical-axis high shear mixer (vHSM) granulators.In the development of the powder flow regime map, two distinct regimes were identified. Ideal roping regime occurs at high impeller speeds when the rotating blades pushes the powder out and up the mixer wall, and then back down the free surface forming the "roping" flow pattern. This stable flow behaviour promotes high vertical bed turnover which is essential for controlled granulation. In this regime, the powder in the blade region has sufficient rotational inertia to overcome gravitational forces (i.e. powder Froude number greater than unity). If this criterion is not met, the mixing system remains in the undesirable bumping regime. This regime is characterised by poor bed turnover and non-uniform shear distribution within the powder bed. In the bumping regime, multiple transitional states are observed with increasing impeller speeds for this particular system, which has not been fully characterised in the literature before. An explanation for the observed apparent roping behaviour based on bed resonance is given. These intermediary transitional states can be differentiated by blade-powder interactions.From these observations, a powder flow regime map for vertical-axis mixer granulators is proposed based on two dimensionless groups: powder Froude number, the ratio of the powder rotational inertial to gravitational forces and the Bed Resonance number, which characterises the interaction of the bulk motion of the powder bed with the passage of impeller blades beneath it. The regime map was validated by experimental results utilising ii iii the well-established, non-invasive tracking technique of Positron Emission Particle Tracking (PEPT) and torque measurements.Investigations into the effect of impeller speed, powder cohesion and blade-rake angle on powder flow and mixing behaviour were conducted using PEPT. Results showed that powder velocity, bed porosity and shear rates varied spatially within the mixer granulator. Studies of the stable roping regime revealed that the average powder velocity in the impeller zone was 1.66 m/s (≈25% of the impeller tip speed). In comparison, the average powder velocity in the circulation and surface zone was approximately half of the impeller zone at 0.9 and 0.74 m/s, respectively (12% and 11% of the impeller tip speed). With the addition of mois...

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Nonmedical applications of a positron camera

Cited by 67 publications

References 6 publications

Geoscientific process monitoring with positron emission tomography (GeoPET)

Geoscientific process monitoring with positron emission tomography (GeoPET)

Characterising porosity of multi-component mixtures in rotary mills

Powder flow in vertical high shear mixer granulators

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