7,267 research outputs found
Generic guide concepts for the European Spallation Source
The construction of the European Spallation Source (ESS) faces many
challenges from the neutron beam transport point of view: The spallation source
is specified as being driven by a 5 MW beam of protons, each with 2 GeV energy,
and yet the requirements in instrument background suppression relative to
measured signal vary between 10 and 10. The energetic particles,
particularly above 20 MeV, which are expected to be produced in abundance in
the target, have to be filtered in order to make the beamlines safe,
operational and provide good quality measurements with low background.
We present generic neutron guides of short and medium length instruments
which are optimized for good performance at minimal cost. Direct line of sight
to the source is avoided twice, with either the first point out of line of
sight or both being inside the bunker (20\,m) to minimize shielding costs.
These guide geometries are regarded as a baseline to define standards for
instruments to be constructed at ESS. They are used to find commonalities and
develop principles and solutions for common problems. Lastly, we report the
impact of employing the over-illumination concept to mitigate losses from
random misalignment passively, and that over-illumination should be used
sparingly in key locations to be effective. For more widespread alignment
issues, a more direct, active approach is likely to be needed
MeV Neutron Production from Thermal Neutron Capture in {6}^Li Simulated with Geant4
Various Li compounds are commonly used at neutron facilities as neutron
absorbers. These compounds provide one of the highest ratios of neutron
attenuation to -ray production. Unfortunately, the usage of these
compounds can also give rise to fast neutron emission with energies up to
almost 16 MeV. Historically, some details in this fast neutron production
mechanism can be absent from some modeling packages under some optimization
scenarios. In this work, we tested Geant4 to assess the performance of this
simulation toolkit for the fast neutron generation mechanism. We compare the
results of simulations performed with Geant4 to available measurements. The
outcome of our study shows that results of the Geant4 simulations are in good
agreement with the available measurements for Li fast neutron production,
and suitable for neutron instrument background evaluation at spallation neutron
sources.Comment: 6 pages, 3 figures, Proceeding of The Sixth European Conference on
Neutron Scattering, Zaragoza Spain, August 30 to September 4 201
Battery health determination by subspace parameter estimation and sliding mode control for an all-electric Personal Rapid Transit vehicle â the ULTra
The paper describes a real-time adaptive battery modelling methodology for use in an all electric personal rapid transit (PRT) vehicle. Through use of a sliding-mode observer and online subspace parameter estimation, the voltages associated with monitoring the state of charge (SoC) of the battery system are shown to be accurately estimated, even with erroneous initial conditions in both the model and parameters. In this way, problems such as self- discharge during storage of the cells and SoC drift (as usually incurred by coulomb-counting methods due to overcharging or ambient temperature fluctuations) are overcome. Moreover, through online monitoring of the degradation of the estimated parameters, battery ageing (State of Health) can be monitored and, in the case of safety- critical systems, cell failure may be predicted in time to avoid inconvenience to passenger networks. Due to the adaptive nature of the proposed methodology, this system can be implemented over a wide range of operating environments, applications and battery topologies, by adjustment of the underlying state-space model
In-Beam Background Suppression Shield
The long (3ms) proton pulse of the European Spallation Source (ESS) gives
rise to unique and potentially high backgrounds for the instrument suite. In
such a source an instrument capabilities will be limited by it's Signal to
Noise (S/N) ratio. The instruments with a direct view of the moderator, which
do not use a bender to help mitigate the fast neutron background, are the most
challenging. For these beam lines we propose the innovative shielding of
placing blocks of material directly into the guide system, which allow a
minimum attenuation of the cold and thermal fluxes relative to the background
suppression. This shielding configuration has been worked into a beam line
model using Geant4. We study particularly the advantages of single crystal
sapphire and silicon blocks .Comment: 12 pages, 8 figures, proceeding of NDS 2015, 4th International
Workshop on Neutron Delivery Systems, 28 -30 September 2015, ILL Grenoble,
Franc
Measurements and Monte-Carlo simulations of the particle self-shielding effect of B4C grains in neutron shielding concrete
A combined measurement and Monte-Carlo simulation study was carried out in
order to characterize the particle self-shielding effect of B4C grains in
neutron shielding concrete. Several batches of a specialized neutron shielding
concrete, with varying B4C grain sizes, were exposed to a 2 {\AA} neutron beam
at the R2D2 test beamline at the Institute for Energy Technology located in
Kjeller, Norway. The direct and scattered neutrons were detected with a neutron
detector placed behind the concrete blocks and the results were compared to
Geant4 simulations. The particle self-shielding effect was included in the
Geant4 simulations by calculating effective neutron cross-sections during the
Monte-Carlo simulation process. It is shown that this method well reproduces
the measured results. Our results show that shielding calculations for
low-energy neutrons using such materials would lead to an underestimate of the
shielding required for a certain design scenario if the particle self-shielding
effect is not included in the calculations.Comment: This manuscript version is made available under the CC-BY-NC-ND 4.0
license http://creativecommons.org/licenses/by-nc-nd/4.0
DRINet for medical image segmentation
Convolutional neural networks (CNNs) have revolutionized medical image analysis over the past few years. The UNet architecture is one of the most well-known CNN architectures for semantic segmentation and has achieved remarkable successes in many different medical image segmentation applications. The U-Net architecture consists of standard convolution layers, pooling layers, and upsampling layers. These convolution layers learn representative features of input images and construct segmentations based on the features. However, the features learned by standard convolution layers are not distinctive when the differences among different categories are subtle in terms of intensity, location, shape, and size. In this paper, we propose a novel CNN architecture, called Dense-Res-Inception Net (DRINet), which addresses this challenging problem. The proposed DRINet consists of three blocks, namely a convolutional block with dense connections, a deconvolutional block with residual Inception modules, and an unpooling block. Our proposed architecture outperforms the U-Net in three different challenging applications, namely multi-class segmentation of cerebrospinal fluid (CSF) on brain CT images, multi-organ segmentation on abdominal CT images, multi-class brain tumour segmentation on MR images
Political trials and the suppression of popular radicalism in England, 1799-1820
This chapter examines the decision-making process between the Home Office and the governmentâs law officers in prosecuting individuals for sedition and treason in the period 1799â1820. The term state trial suggests a more centralised and government-led repression of popular radicalism than the process was in practice. Provincial reformers also faced the complex layers of their local justice system, which was more loyalist, committed to stamping out political radicalism. The trial of the âThirty Eightâ Manchester radicals in June 1812 demonstrates the mutable definitions of treason, sedition and processes of justice in the theatre of the court.Peer reviewe
Ovalbumin sensitization and challenge increases the number of lung cells possessing a mesenchymal stromal cell phenotype
Abstract Background Recent studies have indicated the presence of multipotent mesenchymal stromal cells (MSCs) in human lung diseases. Excess airway smooth muscle, myofibroblasts and activated fibroblasts have each been noted in asthma, suggesting that mesenchymal progenitor cells play a role in asthma pathogenesis. We therefore sought to determine whether MSCs are present in the lungs of ovalbumin (OVA)-sensitized and challenged mice, a model of allergic airways disease. Methods Balb/c mice were sensitized and challenged with PBS or OVA over a 25 day period. Flow cytometry as well as colony forming and differentiation potential were used to analyze the emergence of MSCs along with gene expression studies using immunochemical analyses, quantitative polymerase chain reaction (qPCR), and gene expression beadchips. Results A CD45-negative subset of cells expressed Stro-1, Sca-1, CD73 and CD105. Selection for these markers and negative selection against CD45 yielded a population of cells capable of adipogenic, osteogenic and chondrogenic differentiation. Lungs from OVA-treated mice demonstrated a greater average colony forming unit-fibroblast (CFU-F) than control mice. Sorted cells differed from unsorted lung adherent cells, exhibiting a pattern of gene expression nearly identical to bone marrow-derived sorted cells. Finally, cells isolated from the bronchoalveolar lavage of a human asthma patient showed identical patterns of cell surface markers and differentiation potential. Conclusions In summary, allergen sensitization and challenge is accompanied by an increase of MSCs resident in the lungs that may regulate inflammatory and fibrotic responses.http://deepblue.lib.umich.edu/bitstream/2027.42/78265/1/1465-9921-11-127.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78265/2/1465-9921-11-127.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/78265/3/1465-9921-11-127-S1.DOCPeer Reviewe
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