13,069 research outputs found
Analysis of parametric biological models with non-linear dynamics
In this paper we present recent results on parametric analysis of biological
models. The underlying method is based on the algorithms for computing
trajectory sets of hybrid systems with polynomial dynamics. The method is then
applied to two case studies of biological systems: one is a cardiac cell model
for studying the conditions for cardiac abnormalities, and the second is a
model of insect nest-site choice.Comment: In Proceedings HSB 2012, arXiv:1208.315
Quasi-Relative Interiors for Graphs of Convex Set-Valued Mappings
This paper aims at providing further studies of the notion of quasi-relative
interior for convex sets introduced by Borwein and Lewis. We obtain new
formulas for representing quasi-relative interiors of convex graphs of
set-valued mappings and for convex epigraphs of extended-real-valued functions
defined on locally convex topological vector spaces. We also show that the
role, which this notion plays in infinite dimensions and the results obtained
in this vein, are similar to those involving relative interior in
finite-dimensional spaces.Comment: This submission replaces our previous version
Learning a local-variable model of aromatic and conjugated systems
A collection of new
approaches to building and training neural
networks, collectively referred to as deep learning, are attracting
attention in theoretical chemistry. Several groups aim to replace
computationally expensive <i>ab initio</i> quantum mechanics
calculations with learned estimators. This raises questions about
the representability of complex quantum chemical systems with neural
networks. Can local-variable models efficiently approximate nonlocal
quantum chemical features? Here, we find that convolutional architectures,
those that only aggregate information locally, cannot efficiently
represent aromaticity and conjugation in large systems. They cannot
represent long-range nonlocality known to be important in quantum
chemistry. This study uses aromatic and conjugated systems computed
from molecule graphs, though reproducing quantum simulations is the
ultimate goal. This task, by definition, is both computable and known
to be important to chemistry. The failure of convolutional architectures
on this focused task calls into question their use in modeling quantum
mechanics. To remedy this heretofore unrecognized deficiency, we introduce
a new architecture that propagates information back and forth in waves
of nonlinear computation. This architecture is still a local-variable
model, and it is both computationally and representationally efficient,
processing molecules in sublinear time with far fewer parameters than
convolutional networks. Wave-like propagation models aromatic and
conjugated systems with high accuracy, and even models the impact
of small structural changes on large molecules. This new architecture
demonstrates that some nonlocal features of quantum chemistry can
be efficiently represented in local variable models
Effects of aluminum on hydrogen solubility and diffusion in deformed Fe-Mn alloys
We discuss hydrogen diffusion and solubility in aluminum alloyed Fe-Mn
alloys. The systems of interest are subjected to tetragonal and isotropic
deformations. Based on ab initio modelling, we calculate solution energies,
then employ Oriani's theory which reflects the influence of Al alloying via
trap site diffusion. This local equilibrium model is complemented by
qualitative considerations of Einstein diffusion. Therefore, we apply the
climbing image nudged elastic band method to compute the minimum energy paths
and energy barriers for hydrogen diffusion. Both for diffusivity and solubility
of hydrogen, we find that the influence of the substitutional Al atom has both
local chemical and nonlocal volumetric contributions.Comment: 9 page
Chinese Firms’ Political Connection, Ownership, and Financing Constraints
We empirically examine some listed Chinese firms’ political connection, ownership, and financing constraints. Politically-connected firms display no financing constraints whereas firms without connection experience significant constraints. Non-connected family-controlled firms bear greater constraints than non-connected state-owned firms.Political connection; investments; financing constraints; Chinese firms
Financial liberalization and financing constraints: some evidence from panel data of listed Chinese firms
This paper examines the impact of recent financial liberalization in China on the financing constraints and investment of publicly-listed Chinese firms. Two continuous indices are constructed to measure the evolution and intensity of financial reforms: a financial liberalization index and a capital control index. Dynamic panel GMM method is used to estimate firms’ financing constraints in an Euler-equation investment model. The results indicate that while smaller firms face significant financing constraints than larger firms, financial liberalization has raised the financing constraints for the latter and failed to relieve the constraints for the former. It appears financial reforms in China have subjected larger firms to greater market discipline but the reforms probably have not been profound enough to benefit smaller firms.Financial liberalization; investments; financing constraints; Chinese firms
Enriching Knowledge Bases with Counting Quantifiers
Information extraction traditionally focuses on extracting relations between
identifiable entities, such as . Yet, texts
often also contain Counting information, stating that a subject is in a
specific relation with a number of objects, without mentioning the objects
themselves, for example, "California is divided into 58 counties". Such
counting quantifiers can help in a variety of tasks such as query answering or
knowledge base curation, but are neglected by prior work. This paper develops
the first full-fledged system for extracting counting information from text,
called CINEX. We employ distant supervision using fact counts from a knowledge
base as training seeds, and develop novel techniques for dealing with several
challenges: (i) non-maximal training seeds due to the incompleteness of
knowledge bases, (ii) sparse and skewed observations in text sources, and (iii)
high diversity of linguistic patterns. Experiments with five human-evaluated
relations show that CINEX can achieve 60% average precision for extracting
counting information. In a large-scale experiment, we demonstrate the potential
for knowledge base enrichment by applying CINEX to 2,474 frequent relations in
Wikidata. CINEX can assert the existence of 2.5M facts for 110 distinct
relations, which is 28% more than the existing Wikidata facts for these
relations.Comment: 16 pages, The 17th International Semantic Web Conference (ISWC 2018
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