157 research outputs found
Joint Cuts and Matching of Partitions in One Graph
As two fundamental problems, graph cuts and graph matching have been
investigated over decades, resulting in vast literature in these two topics
respectively. However the way of jointly applying and solving graph cuts and
matching receives few attention. In this paper, we first formalize the problem
of simultaneously cutting a graph into two partitions i.e. graph cuts and
establishing their correspondence i.e. graph matching. Then we develop an
optimization algorithm by updating matching and cutting alternatively, provided
with theoretical analysis. The efficacy of our algorithm is verified on both
synthetic dataset and real-world images containing similar regions or
structures
Molecular Conformation Generation via Shifting Scores
Molecular conformation generation, a critical aspect of computational
chemistry, involves producing the three-dimensional conformer geometry for a
given molecule. Generating molecular conformation via diffusion requires
learning to reverse a noising process. Diffusion on inter-atomic distances
instead of conformation preserves SE(3)-equivalence and shows superior
performance compared to alternative techniques, whereas related generative
modelings are predominantly based upon heuristical assumptions. In response to
this, we propose a novel molecular conformation generation approach driven by
the observation that the disintegration of a molecule can be viewed as casting
increasing force fields to its composing atoms, such that the distribution of
the change of inter-atomic distance shifts from Gaussian to Maxwell-Boltzmann
distribution. The corresponding generative modeling ensures a feasible
inter-atomic distance geometry and exhibits time reversibility. Experimental
results on molecular datasets demonstrate the advantages of the proposed
shifting distribution compared to the state-of-the-art.Comment: 18 pages, 7 figure
Federated Learning for Semantic Parsing: Task Formulation, Evaluation Setup, New Algorithms
This paper studies a new task of federated learning (FL) for semantic
parsing, where multiple clients collaboratively train one global model without
sharing their semantic parsing data. By leveraging data from multiple clients,
the FL paradigm can be especially beneficial for clients that have little
training data to develop a data-hungry neural semantic parser on their own. We
propose an evaluation setup to study this task, where we re-purpose widely-used
single-domain text-to-SQL datasets as clients to form a realistic heterogeneous
FL setting and collaboratively train a global model. As standard FL algorithms
suffer from the high client heterogeneity in our realistic setup, we further
propose a novel LOss Reduction Adjusted Re-weighting (Lorar) mechanism to
mitigate the performance degradation, which adjusts each client's contribution
to the global model update based on its training loss reduction during each
round. Our intuition is that the larger the loss reduction, the further away
the current global model is from the client's local optimum, and the larger
weight the client should get. By applying Lorar to three widely adopted FL
algorithms (FedAvg, FedOPT and FedProx), we observe that their performance can
be improved substantially on average (4%-20% absolute gain under MacroAvg) and
that clients with smaller datasets enjoy larger performance gains. In addition,
the global model converges faster for almost all the clients.Comment: ACL 2023 long pape
Variational Wasserstein Barycenters for Geometric Clustering
We propose to compute Wasserstein barycenters (WBs) by solving for Monge maps
with variational principle. We discuss the metric properties of WBs and explore
their connections, especially the connections of Monge WBs, to K-means
clustering and co-clustering. We also discuss the feasibility of Monge WBs on
unbalanced measures and spherical domains. We propose two new problems --
regularized K-means and Wasserstein barycenter compression. We demonstrate the
use of VWBs in solving these clustering-related problems
Cu-In Halide Perovskite solar absorbers
The long-term chemical instability and the presence of toxic Pb in otherwise
stellar solar absorber APbX have hindered their large-scale
commercialization. Previously explored ways to achieve Pb-free halide
perovskites involved replacing Pb with other similar M cations in
ns electron configuration, e.g., Sn or by Bi (plus Ag),
but unfortunately this showed either poor stability (M = Sn) or weakly
absorbing oversized indirect gaps (M = Bi), prompting concerns that perhaps
stability and good optoelectronic properties might be contraindicated. Herein,
we exploit the electronic structure underpinning of classic Cu[In,Ga]Se
(CIGS) chalcopyrite solar absorbers to design Pb-free halide perovskites by
transmuting 2Pb to the pair [B + C]. The resulting group of
double perovskites with formula ABCX (A = K, Rb, Cs; B = Cu, Ag; C =
Ga, In; X = Cl, Br, I) benefits from the ionic, yet narrow-gap character of
halide perovskites, and at the same time borrows the advantage of the strong
and rapidly rising Cu(d)/Se(p) Ga/In(s/p)
valence-to-conduction-band absorption spectra known from CIGS. This constitutes
a new group of CuIn-based Halide Perovskite (CIHP). Our first-principles
calculations guided by such design principles indicate that the CIHPs class has
members with clear thermodynamic stability, showing rather strong direct-gap
optical transitions, and manifesting a wide-range of tunable gap values (from
zero to about 2.5 eV) and combination of light electron and heavy-light hole
effective masses. Materials screening of candidate CHIPs then identifies the
best-of-class Rb[CuIn]Cl, Rb[AgIn]Br and Cs[AgIn]Br,
having direct band gaps of 1.36, 1.46 and 1.50 eV, and a theoretical
spectroscopic limited maximal efficiency comparable to chalcopyrites and
CHNHPbI.Comment: 25 pages, 6 figure
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