12,805 research outputs found
Preliminary Feasibility of Dedicated Breast CT With an Inverse Geometry
In this study we theoretically investigated the minimum scan time of an inverse-geometry dedicated breast CT system that provides sufficient sampling and dose equivalent to mammography without exceeding the limits of source power or detector count rate. The inverse geometry, which utilizes a large-area scanned source and a narrower photon-counting detector, is expected to have improved dose efficiency compared to cone-beam methods due to reduced scatter effects and improved detector efficiency. The analysis assumed the specifications of available inverse-geometry source and detector hardware (SBDX, NovaRay, Inc, Newark CA). The scan time was calculated for a 10, 14, and 18-cm diameter breast composed of 50% glandular / 50% adipose tissue. The results demonstrate a minimum scan time of 6.5, 14.3, and 14.7 seconds for a 10, 14, and 18-cm-diameter breast, respectively. The scan times are comparable to those of proposed cone-beam systems. For all three breast sizes, the scan time was limited by the detector count rate. For example, for the 14-cm-diameter breast, the minimum scan time that met the source power limitation was 1.1 seconds, and the minimum scan time that achieved sufficient sampling was 0.8 seconds. The scan time can be reduced by increasing the detector count rate or area. Effective bowtie filters will be required to prevent detector saturation at the object edges. Overall, the results support preliminary feasibility of dedicated breast CT with an inverse geometry
Quantitative characterization of pore structure of several biochars with 3D imaging
Pore space characteristics of biochars may vary depending on the used raw
material and processing technology. Pore structure has significant effects on
the water retention properties of biochar amended soils. In this work, several
biochars were characterized with three-dimensional imaging and image analysis.
X-ray computed microtomography was used to image biochars at resolution of 1.14
m and the obtained images were analysed for porosity, pore-size
distribution, specific surface area and structural anisotropy. In addition,
random walk simulations were used to relate structural anisotropy to diffusive
transport. Image analysis showed that considerable part of the biochar volume
consist of pores in size range relevant to hydrological processes and storage
of plant available water. Porosity and pore-size distribution were found to
depend on the biochar type and the structural anisotopy analysis showed that
used raw material considerably affects the pore characteristics at micrometre
scale. Therefore attention should be paid to raw material selection and quality
in applications requiring optimized pore structure.Comment: 16 pages, 4 figures. The final publication is available at Springer
via http://dx.doi.org/10.1007/s11356-017-8823-
Eavesdropping Whilst You're Shopping: Balancing Personalisation and Privacy in Connected Retail Spaces
Physical retailers, who once led the way in tracking with loyalty cards and
`reverse appends', now lag behind online competitors. Yet we might be seeing
these tables turn, as many increasingly deploy technologies ranging from simple
sensors to advanced emotion detection systems, even enabling them to tailor
prices and shopping experiences on a per-customer basis. Here, we examine these
in-store tracking technologies in the retail context, and evaluate them from
both technical and regulatory standpoints. We first introduce the relevant
technologies in context, before considering privacy impacts, the current
remedies individuals might seek through technology and the law, and those
remedies' limitations. To illustrate challenging tensions in this space we
consider the feasibility of technical and legal approaches to both a) the
recent `Go' store concept from Amazon which requires fine-grained, multi-modal
tracking to function as a shop, and b) current challenges in opting in or out
of increasingly pervasive passive Wi-Fi tracking. The `Go' store presents
significant challenges with its legality in Europe significantly unclear and
unilateral, technical measures to avoid biometric tracking likely ineffective.
In the case of MAC addresses, we see a difficult-to-reconcile clash between
privacy-as-confidentiality and privacy-as-control, and suggest a technical
framework which might help balance the two. Significant challenges exist when
seeking to balance personalisation with privacy, and researchers must work
together, including across the boundaries of preferred privacy definitions, to
come up with solutions that draw on both technology and the legal frameworks to
provide effective and proportionate protection. Retailers, simultaneously, must
ensure that their tracking is not just legal, but worthy of the trust of
concerned data subjects.Comment: 10 pages, 1 figure, Proceedings of the PETRAS/IoTUK/IET Living in the
Internet of Things Conference, London, United Kingdom, 28-29 March 201
- …