11,753 research outputs found
Plankton functional group models – An assessment
This Discussant’s Report provides a summary of the discussions that followed presentation of the approaches and ideas described in Thingstad et al. (this volume). The discussions, which addressed aspects of conceptual understanding and parameterization that are relevant to development of ecosystem models capable of emergent behavior at a range of scales, the benefits of functional group modeling, and some of the limitations of this approach, provide insights that are relevant to setting directions for future research efforts. One important point emerging from the discussions was that reconciling the requirements of simplicity versus complexity with the desire to obtain predictive capability is an important area where biogeochemical and ecosystem models can be improved
Riesz Transform on Locally Symmetric Spaces and Riemannian Manifolds with a Spectral Gap
In this paper we study the Riesz transform on complete and connected
Riemannian manifolds with a certain spectral gap in the spectrum of
the Laplacian. We show that on such manifolds the Riesz transform is
bounded for all . This generalizes a result by Mandouvalos
and Marias and extends a result by Auscher, Coulhon, Duong, and Hofmann to the
case where zero is an isolated point of the spectrum of the Laplacian.Comment: 8 p
Policy-Aware Unbiased Learning to Rank for Top-k Rankings
Counterfactual Learning to Rank (LTR) methods optimize ranking systems using
logged user interactions that contain interaction biases. Existing methods are
only unbiased if users are presented with all relevant items in every ranking.
There is currently no existing counterfactual unbiased LTR method for top-k
rankings. We introduce a novel policy-aware counterfactual estimator for LTR
metrics that can account for the effect of a stochastic logging policy. We
prove that the policy-aware estimator is unbiased if every relevant item has a
non-zero probability to appear in the top-k ranking. Our experimental results
show that the performance of our estimator is not affected by the size of k:
for any k, the policy-aware estimator reaches the same retrieval performance
while learning from top-k feedback as when learning from feedback on the full
ranking. Lastly, we introduce novel extensions of traditional LTR methods to
perform counterfactual LTR and to optimize top-k metrics. Together, our
contributions introduce the first policy-aware unbiased LTR approach that
learns from top-k feedback and optimizes top-k metrics. As a result,
counterfactual LTR is now applicable to the very prevalent top-k ranking
setting in search and recommendation.Comment: SIGIR 2020 full conference pape
Kim Hofmann
With over 25 years’ experience, Kim has extensive skills in multiple aspects of management, cost control, training, DISC, and customer service (and she is a past school nutrition director). She is a Trainer/Consultant and eLearning developer for ICN, and a certified trainer for DISC training. She has published numerous articles for Carroll Service’s Child Nutrition Professional’s magazine, has presented at many SNA conferences, taught Food Systems Management at the University of Akron, was a cost control specialist for US Foods, and was a trainer for Career Track/Fred Pryor specializing in management training.https://egrove.olemiss.edu/icn_ohistories/1071/thumbnail.jp
Dynamics of strong and radiative decays of Ds-mesons in the hadrogenesis conjecture
The positive parity scalar D(2317) and axial-vector D(2460)
charmed strange mesons are generated by coupled-channel dynamics through the
s-wave scattering of Goldstone bosons off the pseudoscalar and vector
D(D)-meson ground states. The specific masses of these states are obtained
as a consequence of the attraction arising from the Weinberg-Tomozawa
interaction in the chiral Lagrangian. Chiral corrections to order Q
are calculated and found to be small. The D(2317) and D(2460)
mesons decay either strongly into the isospin-violating D and
D channels or electromagnetically. We show that the -
and (KD-KD) mixings act constructively to generate strong
widths of the order of 140 keV and emphasize the sensitivity of this value to
the component of the states. The one-loop contribution to the radiative
decay amplitudes of scalar and axial-vector states is calculated using the
electromagnetic Lagrangian to chiral order Q. We show the importance
of taking into account processes involving light vector mesons explicitly in
the dynamics of electromagnetic decays. The radiative width are sensitive to
both and components, hence providing information complementary
to the strong widths on the positive parity -meson structure.Comment: 4 pages, Invited Contribution to QNP09, Beijing, September 21-26,
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