4,379 research outputs found
Digital Complex Correlator for a C-band Polarimetry survey
The international Galactic Emission Mapping project aims to map and
characterize the polarization field of the Milky Way. In Portugal it will
cartograph the C-band sky polarized emission of the Northern Hemisphere and
provide templates for map calibration and foreground control of microwave space
probes like ESA Planck Surveyor mission. The receiver system is equipped with a
novel receiver with a full digital back-end using an Altera Field Programmable
Gate Array, having a very favorable cost/performance relation. This new digital
backend comprises a base-band complex cross-correlator outputting the four
Stokes parameters of the incoming polarized radiation. In this document we
describe the design and implementation of the complex correlator using COTS
components and a processing FPGA, detailing the method applied in the several
algorithm stages and suitable for large sky area surveys.Comment: 15 pages, 10 figures; submitted to Experimental Astronomy, Springe
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Investigating distributed simulation with COTS simulation packages: Experiences with Simul8 and the HLA
Commercial-off-the-shelf simulation packages (CSPs) are used widely in industry. Several research groups are currently working towards the creation of distributed simulation with these CSPs. The motivations to do this are various and are largely unproven as there are very few good examples of this kind of distributed simulation in practice. Our goal is therefore to create a distributed simulation environment using CSPs that will allow end users to make their own decisions as to whether this technology will be useful. This paper presents continuing research in creating such an environment using the CSP Simul8 and the High Level Architecture, the IEEE 1516 standard for distributed simulation. The scope of this paper is limited to the CSPI-PDG Type I Interoperability Reference Model
Parallel Discrete Event Simulation with Erlang
Discrete Event Simulation (DES) is a widely used technique in which the state
of the simulator is updated by events happening at discrete points in time
(hence the name). DES is used to model and analyze many kinds of systems,
including computer architectures, communication networks, street traffic, and
others. Parallel and Distributed Simulation (PADS) aims at improving the
efficiency of DES by partitioning the simulation model across multiple
processing elements, in order to enabling larger and/or more detailed studies
to be carried out. The interest on PADS is increasing since the widespread
availability of multicore processors and affordable high performance computing
clusters. However, designing parallel simulation models requires considerable
expertise, the result being that PADS techniques are not as widespread as they
could be. In this paper we describe ErlangTW, a parallel simulation middleware
based on the Time Warp synchronization protocol. ErlangTW is entirely written
in Erlang, a concurrent, functional programming language specifically targeted
at building distributed systems. We argue that writing parallel simulation
models in Erlang is considerably easier than using conventional programming
languages. Moreover, ErlangTW allows simulation models to be executed either on
single-core, multicore and distributed computing architectures. We describe the
design and prototype implementation of ErlangTW, and report some preliminary
performance results on multicore and distributed architectures using the well
known PHOLD benchmark.Comment: Proceedings of ACM SIGPLAN Workshop on Functional High-Performance
Computing (FHPC 2012) in conjunction with ICFP 2012. ISBN: 978-1-4503-1577-
DEEPMIR: A DEEP neural network for differential detection of cerebral Microbleeds and IRon deposits in MRI
Lobar cerebral microbleeds (CMBs) and localized non-hemorrhage iron deposits
in the basal ganglia have been associated with brain aging, vascular disease
and neurodegenerative disorders. Particularly, CMBs are small lesions and
require multiple neuroimaging modalities for accurate detection. Quantitative
susceptibility mapping (QSM) derived from in vivo magnetic resonance imaging
(MRI) is necessary to differentiate between iron content and mineralization. We
set out to develop a deep learning-based segmentation method suitable for
segmenting both CMBs and iron deposits. We included a convenience sample of 24
participants from the MESA cohort and used T2-weighted images, susceptibility
weighted imaging (SWI), and QSM to segment the two types of lesions. We
developed a protocol for simultaneous manual annotation of CMBs and
non-hemorrhage iron deposits in the basal ganglia. This manual annotation was
then used to train a deep convolution neural network (CNN). Specifically, we
adapted the U-Net model with a higher number of resolution layers to be able to
detect small lesions such as CMBs from standard resolution MRI. We tested
different combinations of the three modalities to determine the most
informative data sources for the detection tasks. In the detection of CMBs
using single class and multiclass models, we achieved an average sensitivity
and precision of between 0.84-0.88 and 0.40-0.59, respectively. The same
framework detected non-hemorrhage iron deposits with an average sensitivity and
precision of about 0.75-0.81 and 0.62-0.75, respectively. Our results showed
that deep learning could automate the detection of small vessel disease lesions
and including multimodal MR data (particularly QSM) can improve the detection
of CMB and non-hemorrhage iron deposits with sensitivity and precision that is
compatible with use in large-scale research studies
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