839 research outputs found
sputniPIC: an Implicit Particle-in-Cell Code for Multi-GPU Systems
Large-scale simulations of plasmas are essential for advancing our
understanding of fusion devices, space, and astrophysical systems.
Particle-in-Cell (PIC) codes have demonstrated their success in simulating
numerous plasma phenomena on HPC systems. Today, flagship supercomputers
feature multiple GPUs per compute node to achieve unprecedented computing power
at high power efficiency. PIC codes require new algorithm design and
implementation for exploiting such accelerated platforms. In this work, we
design and optimize a three-dimensional implicit PIC code, called sputniPIC, to
run on a general multi-GPU compute node. We introduce a particle decomposition
data layout, in contrast to domain decomposition on CPU-based implementations,
to use particle batches for overlapping communication and computation on GPUs.
sputniPIC also natively supports different precision representations to achieve
speed up on hardware that supports reduced precision. We validate sputniPIC
through the well-known GEM challenge and provide performance analysis. We test
sputniPIC on three multi-GPU platforms and report a 200-800x performance
improvement with respect to the sputniPIC CPU OpenMP version performance. We
show that reduced precision could further improve performance by 45% to 80% on
the three platforms. Because of these performance improvements, on a single
node with multiple GPUs, sputniPIC enables large-scale three-dimensional PIC
simulations that were only possible using clusters.Comment: Accepted for publication at the 32nd International Symposium on
Computer Architecture and High Performance Computing (SBAC-PAD 2020
EFSUMB Recommendations and Guidelines for Gastrointestinal Ultrasound - Part 1: Examination Techniques and Normal Findings (Short version)
Abstract
▼
In October 2014 the European Federation of Societies
for Ultrasound in Medicine and Biology formed
a Gastrointestinal Ultrasound (GIUS) task force
group to promote the use of GIUS in a clinical setting.
One of the main objectives of the task force
group was to develop clinical recommendations
and guidelines for the use of GIUS under the auspices
of EFSUMB. The first part, gives an overview of
the examination techniques for GIUS recommended
by experts in the field. It also presents the
current evidence for the interpretation of normal
sonoanatomical and physiological features as examined
with different ultrasound modalities
EFSUMB Recommendations and Guidelines for Gastrointestinal Ultrasound - Part 1: Examination Techniques and Normal Findings (Long version).
Abstract
▼
In October 2014 the European Federation of Societies
for Ultrasound in Medicine and Biology formed
a Gastrointestinal Ultrasound (GIUS) task force
group to promote the use of GIUS in a clinical setting.
One of the main objectives of the task force
group was to develop clinical recommendations
and guidelines for the use of GIUS under the auspices
of EFSUMB. The first part, gives an overview of
the examination techniques for GIUS recommended
by experts in the field. It also presents the
current evidence for the interpretation of normal
sonoanatomical and physiological features as examined
with different ultrasound modalities
AUTONOMOUS FORMATION KEEPING AND RECONFIGURATION FOR REMOTE SENSING SPACECRAFT
ABSTRACT This paper is devoted to the realistic demonstration of a complete Guidance, Navigation and Control (GNC) system for formation flying spacecraft in Low Earth orbit (LEO). Numerous technical novelties in the areas of formation flying guidance, GPS-based relative navigation, and impulsive relative orbit control have made this possible, but the primary contribution of this research work stems from the design and implementation of a comprehensive formation flying system through the successful integration of various techniques. This research has led to the full development, testing and validation of the GNC flight code to be embedded in the on-board computer of the Main spacecraft of the Swedish PRISMA technology demonstration. Furthermore key guidance and control algorithms presented here are going to be demonstrated for the first time on-board the German TanDEM-X formation flying mission. Overall this paper focuses on realistic application cases closely related to upcoming formation flying missions. The intention is to realize a practical and reliable way to a technology which is discussed and studied since decades but is still confined in research laboratories. Hardwarein-the-loop real-time simulations including flight computers show that simple techniques, which exploit the natural orbit motion to full extent, can meet the demanding requirements of the long-term close formation flying
Origin and Properties of the Gap in the Half-Ferromagnetic Heusler Alloys
We study the origin of the gap and the role of chemical composition in the
half-ferromagnetic Heusler alloys using the full-potential screened KKR method.
In the paramagnetic phase the C1_b compounds, like NiMnSb, present a gap.
Systems with 18 valence electrons, Z_t, per unit cell, like CoTiSb, are
semiconductors, but when Z_t > 18 antibonding states are also populated, thus
the paramagnetic phase becomes unstable and the half-ferromagnetic one is
stabilized. The minority occupied bands accommodate a total of nine electrons
and the total magnetic moment per unit cell in mu_B is just the difference
between Z_t and . While the substitution of the transition metal
atoms may preserve the half-ferromagnetic character, substituting the atom
results in a practically rigid shift of the bands and the loss of
half-metallicity. Finally we show that expanding or contracting the lattice
parameter by 2% preserves the minority-spin gap.Comment: 11 pages, 7 figures New figures, revised tex
Constructing masculinities in the National Rugby League's footy show
The research uses content analysis and inclusive masculinity theory in order to explore and explain the construction of esteemed and subjugated masculinities within the context of Australia’s National Rugby League’s (NRL) Footy Show. Results suggest that despite previous research on NRL players, which finds inclusive masculinities dominate, this television show instead attempts to construct orthodox versions of masculinity. We suggest that the Footy Show thus occupies a liminal state in regards to masculinities; attempting to portray, construct and endorse orthodox masculinities, whilst showcasing athletes that more closely align with the social trends of inclusive masculinities
Development and Validation of the Behavioral Tendencies Questionnaire
At a fundamental level, taxonomy of behavior and behavioral tendencies can be described
in terms of approach, avoid, or equivocate (i.e., neither approach nor avoid). While there are
numerous theories of personality, temperament, and character, few seem to take advantage
of parsimonious taxonomy. The present study sought to implement this taxonomy by
creating a questionnaire based on a categorization of behavioral temperaments/tendencies
first identified in Buddhist accounts over fifteen hundred years ago. Items were developed
using historical and contemporary texts of the behavioral temperaments, described as
“Greedy/Faithful”, “Aversive/Discerning”, and “Deluded/Speculative”. To both maintain
this categorical typology and benefit from the advantageous properties of forced-choice
response format (e.g., reduction of response biases), binary pairwise preferences for items
were modeled using Latent Class Analysis (LCA). One sample (n1 = 394) was used to estimate
the item parameters, and the second sample (n2 = 504) was used to classify the participants
using the established parameters and cross-validate the classification against
multiple other measures. The cross-validated measure exhibited good nomothetic span
(construct-consistent relationships with related measures) that seemed to corroborate the
ideas present in the original Buddhist source documents. The final 13-block questionnaire
created from the best performing items (the Behavioral Tendencies Questionnaire or BTQ)
is a psychometrically valid questionnaire that is historically consistent, based in behavioral
tendencies, and promises practical and clinical utility particularly in settings that teach and
study meditation practices such as Mindfulness Based Stress Reduction (MBSR)
Distinguishing Asthma Phenotypes Using Machine Learning Approaches.
Asthma is not a single disease, but an umbrella term for a number of distinct diseases, each of which are caused by a distinct underlying pathophysiological mechanism. These discrete disease entities are often labelled as asthma endotypes. The discovery of different asthma subtypes has moved from subjective approaches in which putative phenotypes are assigned by experts to data-driven ones which incorporate machine learning. This review focuses on the methodological developments of one such machine learning technique-latent class analysis-and how it has contributed to distinguishing asthma and wheezing subtypes in childhood. It also gives a clinical perspective, presenting the findings of studies from the past 5 years that used this approach. The identification of true asthma endotypes may be a crucial step towards understanding their distinct pathophysiological mechanisms, which could ultimately lead to more precise prevention strategies, identification of novel therapeutic targets and the development of effective personalized therapies
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