3,663 research outputs found
Enhancing Hydrogen Generation Through Nanoconfinement of Sensitizers and Catalysts in a Homogeneous Supramolecular Organic Framework.
Enrichment of molecular photosensitizers and catalysts in a confined nanospace is conducive for photocatalytic reactions due to improved photoexcited electron transfer from photosensitizers to catalysts. Herein, the self-assembly of a highly stable 3D supramolecular organic framework from a rigid bipyridine-derived tetrahedral monomer and cucurbit[8]uril in water, and its efficient and simultaneous intake of both [Ru(bpy)3 ]2+ -based photosensitizers and various polyoxometalates, that can take place at very low loading, are reported. The enrichment substantially increases the apparent concentration of both photosensitizer and catalyst in the interior of the framework, which leads to a recyclable, homogeneous, visible light-driven photocatalytic system with 110-fold increase of the turnover number for the hydrogen evolution reaction
Probing Dark Energy with the Kunlun Dark Universe Survey Telescope
Dark energy is an important science driver of many upcoming large-scale
surveys. With small, stable seeing and low thermal infrared background, Dome A,
Antarctica, offers a unique opportunity for shedding light on fundamental
questions about the universe. We show that a deep, high-resolution imaging
survey of 10,000 square degrees in \emph{ugrizyJH} bands can provide
competitive constraints on dark energy equation of state parameters using type
Ia supernovae, baryon acoustic oscillations, and weak lensing techniques. Such
a survey may be partially achieved with a coordinated effort of the Kunlun Dark
Universe Survey Telescope (KDUST) in \emph{yJH} bands over 5000--10,000 deg
and the Large Synoptic Survey Telescope in \emph{ugrizy} bands over the same
area. Moreover, the joint survey can take advantage of the high-resolution
imaging at Dome A to further tighten the constraints on dark energy and to
measure dark matter properties with strong lensing as well as galaxy--galaxy
weak lensing.Comment: 9 pages, 6 figure
Generalized Delayed Feedback Model with Post-Click Information in Recommender Systems
Predicting conversion rate (e.g., the probability that a user will purchase
an item) is a fundamental problem in machine learning based recommender
systems. However, accurate conversion labels are revealed after a long delay,
which harms the timeliness of recommender systems. Previous literature
concentrates on utilizing early conversions to mitigate such a delayed feedback
problem. In this paper, we show that post-click user behaviors are also
informative to conversion rate prediction and can be used to improve
timeliness. We propose a generalized delayed feedback model (GDFM) that unifies
both post-click behaviors and early conversions as stochastic post-click
information, which could be utilized to train GDFM in a streaming manner
efficiently. Based on GDFM, we further establish a novel perspective that the
performance gap introduced by delayed feedback can be attributed to a temporal
gap and a sampling gap. Inspired by our analysis, we propose to measure the
quality of post-click information with a combination of temporal distance and
sample complexity. The training objective is re-weighted accordingly to
highlight informative and timely signals. We validate our analysis on public
datasets, and experimental performance confirms the effectiveness of our
method.Comment: NeurIPS'2
Continuity of weak solutions to an elliptic problem on -fractional Laplacian
In this paper we study an elliptic variational problem regarding the
-fractional Laplacian in on the basis of recent result
\cite{Ha1}, which generalizes the nice work \cite{AT,AP,XZR1}, and then give
some sufficient conditions under which some weak solutions to the above
elliptic variational problem are continuous in . In the final
appendix we correct the proofs of both \cite[Lemma 10]{PXZ1} and \cite[Lemma
A.6]{PXZ} for
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