1,420 research outputs found
Multi-Spacecraft Observations of Recurrent 3He-Rich Solar Energetic Particles
We study the origin of 3He-rich solar energetic particles (<1 MeV/nucleon)
that are observed consecutively on STEREO-B, ACE, and STEREO-A spacecraft when
they are separated in heliolongitude by more than 90{\deg}. The 3He-rich period
on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16,
respectively. The ACE 3He-rich period consists of two sub-events starting on
2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7
3He-rich events with the same sizeable active region producing X-ray flares
accompanied by prompt electron events, when it was near the west solar limb as
seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events
were dispersionless with enormous 3He enrichment, lacking solar energetic
electrons and occurring in corotating interaction regions. We associate these
events with a small, recently emerged active region near the border of a
low-latitude coronal hole that produced numerous jet-like emissions temporally
correlated with type III radio bursts. For the first time we present
observations of 1) solar regions with long-lasting conditions for 3He
acceleration and 2) solar energetic 3He that is temporary
confined/re-accelerated in interplanetary space.Comment: accepted for publication in The Astrophysical Journa
Parallel software tools at Langley Research Center
This document gives a brief overview of parallel software tools available on the Intel iPSC/860 parallel computer at Langley Research Center. It is intended to provide a source of information that is somewhat more concise than vendor-supplied material on the purpose and use of various tools. Each of the chapters on tools is organized in a similar manner covering an overview of the functionality, access information, how to effectively use the tool, observations about the tool and how it compares to similar software, known problems or shortfalls with the software, and reference documentation. It is primarily intended for users of the iPSC/860 at Langley Research Center and is appropriate for both the experienced and novice user
Kernel Spectral Clustering and applications
In this chapter we review the main literature related to kernel spectral
clustering (KSC), an approach to clustering cast within a kernel-based
optimization setting. KSC represents a least-squares support vector machine
based formulation of spectral clustering described by a weighted kernel PCA
objective. Just as in the classifier case, the binary clustering model is
expressed by a hyperplane in a high dimensional space induced by a kernel. In
addition, the multi-way clustering can be obtained by combining a set of binary
decision functions via an Error Correcting Output Codes (ECOC) encoding scheme.
Because of its model-based nature, the KSC method encompasses three main steps:
training, validation, testing. In the validation stage model selection is
performed to obtain tuning parameters, like the number of clusters present in
the data. This is a major advantage compared to classical spectral clustering
where the determination of the clustering parameters is unclear and relies on
heuristics. Once a KSC model is trained on a small subset of the entire data,
it is able to generalize well to unseen test points. Beyond the basic
formulation, sparse KSC algorithms based on the Incomplete Cholesky
Decomposition (ICD) and , , Group Lasso regularization are
reviewed. In that respect, we show how it is possible to handle large scale
data. Also, two possible ways to perform hierarchical clustering and a soft
clustering method are presented. Finally, real-world applications such as image
segmentation, power load time-series clustering, document clustering and big
data learning are considered.Comment: chapter contribution to the book "Unsupervised Learning Algorithms
Corporate Governance, Opaque Bank Activities, and Risk/Return Efficiency: Pre- and Post-Crisis Evidence from Turkey
Does better corporate governance unambiguously improve the risk/return efficiency of banks? Or does either a re-orientation of banks' revenue mix towards more opaque products, an economic downturn, or tighter supervision create off-setting or reinforcing effects? The authors relate bank efficiency to shortfalls from a stochastic risk/return frontier. They analyze how internal governance mechanisms (CEO duality, board experience, political connections, and education profile) and external governance mechanisms (discipline exerted by shareholders, depositors, or skilled employees) determine efficiency in a sample of Turkish banks. The 2000 financial crisis was a wakeup call for bank efficiency and corporate governance. As a result, better corporate governance mechanisms have been able to improve risk/return efficiency when the economic, regulatory, and supervisory environments are more stable and bank products are more complex.corporate governance;bank risk;noninterest income;crisis;frontier
Cohomology of bundles on homological Hopf manifold
We discuss the properties of complex manifolds having rational homology of
including those constructed by Hopf, Kodaira and
Brieskorn-van de Ven. We extend certain previously known vanishing properties
of cohomology of bundles on such manifolds.As an application we consider
degeneration of Hodge-deRham spectral sequence in this non Kahler setting.Comment: To appear in Proceedings of 2007 conference on Several complex
variables and Complex Geometry. Xiamen. Chin
Goal-neglect links Stroop interference with working memory capacity
Relationships between Stroop interference and working memory capacity may reflect individual differences in resolving conflict, susceptibility to goal neglect, or both of these factors. We compared relationships between working memory capacity and three Stroop tasks: a classic, printed color-word Stroop task, a cross-modal Stroop, and a new version of cross-modal Stroop with a concurrent auditory monitoring component. Each of these tasks showed evidence of interference between the semantic meaning of the color word and the to-be-named color, suggesting these tasks each require resolution of interference. However, only Stroop interference in the print-based task with high proportions of congruent trials correlated significantly with working memory capacity. This evidence suggests that the relationships observed between Stroop interference and working memory capacity are primarily driven by individual differences in the propensity to actively maintain a goal. (C) 2012 Elsevier B.V. All rights reserved
Observations of the longitudinal spread of solar energetic particle events in solar cycle 24
With the twin STEREO spacecraft, significantly separated from L1-based satellites such as ACE, simultaneous multi-point measurements of solar energetic particle (SEP) events can be made for H-Fe ions from a few hundred keV/nuc to over 100 MeV/nuc and for electrons from tens to hundreds of keV. These observations allow studies of the longitudinal characteristics of SEP events to advance beyond statistical analysis of single point measurements. Although there have been few large SEP events thus far in cycle 24, there have been a number of smaller events that have been detected by more than one spacecraft. The composition of these SEP events, as indicated by the H/He and Fe/O abundance ratios, shows a dependence on longitudinal distance from the solar source in some events, at times with ratios varying by an order of magnitude. However, these variations are not organized by either the speed or width of the associated coronal mass ejections
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Observations of Past Lunar Landing Sites by the D-CIXS X-Ray Spectrometer on SMART-1
D-CIXS initial observations show a first unambiguous remote sensing of calcium in the lunar regolith. Data obtained are broadly consistent with current understanding of mare and highland composition. Ground truth is provided by the returned Apollo and Luna sample sets
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