1,041 research outputs found
Matching of orbits of certain -expansions with a finite set of digits
In this paper we consider a class of continued fraction expansions: the
so-called -expansions with a finite digit set, where is an
integer. These \emph{-expansions with a finite digit set} were introduced in
[KL,L], and further studied in [dJKN,S]. For fixed they are steered by a
parameter . In [KL], for an explicit interval
was determined, such that for all the entropy
of the underlying Gauss-map is equal. In this
paper we show that for all , , such plateaux exist. In
order to show that the entropy is constant on such plateaux, we obtain the
underlying planar natural extension of the maps , the
-invariant measure, ergodicity, and we show that for any two
from the same plateau, the natural extensions are metrically
isomorphic, and the isomorphism is given explicitly. The plateaux are found by
a property called matching
Stability of port-Hamiltonian systems with mixed time delays subject to input saturation
In this paper, we investigate the stability of port-Hamiltonian systems with mixed time-varying delays as well as input saturation. Three types of time delays, including state delay, input delay, and output delay, are all assumed to be bounded. By introducing the output feedback control law and utilizing serval Lyapunov–Krasovskii functionals, we present three delay-dependent stability criteria in terms of the linear matrix inequality. Meanwhile, we use Wirtinger’s inequality, constraint conditions, and Lyapunov–Krasovskii functionals of triple and quadruple integral form to obtain less conservative results. Some numerical examples demonstrate and support our results
GSAE: an autoencoder with embedded gene-set nodes for genomics functional characterization
Bioinformatics tools have been developed to interpret gene expression data at
the gene set level, and these gene set based analyses improve the biologists'
capability to discover functional relevance of their experiment design. While
elucidating gene set individually, inter gene sets association is rarely taken
into consideration. Deep learning, an emerging machine learning technique in
computational biology, can be used to generate an unbiased combination of gene
set, and to determine the biological relevance and analysis consistency of
these combining gene sets by leveraging large genomic data sets. In this study,
we proposed a gene superset autoencoder (GSAE), a multi-layer autoencoder model
with the incorporation of a priori defined gene sets that retain the crucial
biological features in the latent layer. We introduced the concept of the gene
superset, an unbiased combination of gene sets with weights trained by the
autoencoder, where each node in the latent layer is a superset. Trained with
genomic data from TCGA and evaluated with their accompanying clinical
parameters, we showed gene supersets' ability of discriminating tumor subtypes
and their prognostic capability. We further demonstrated the biological
relevance of the top component gene sets in the significant supersets. Using
autoencoder model and gene superset at its latent layer, we demonstrated that
gene supersets retain sufficient biological information with respect to tumor
subtypes and clinical prognostic significance. Superset also provides high
reproducibility on survival analysis and accurate prediction for cancer
subtypes.Comment: Presented in the International Conference on Intelligent Biology and
Medicine (ICIBM 2018) at Los Angeles, CA, USA and published in BMC Systems
Biology 2018, 12(Suppl 8):14
MicroRNA-like RNAs from the same miRNA precursors play a role in cassava chilling responses
Abstract MicroRNAs (miRNAs) are known to play important roles in various cellular processes and stress responses. MiRNAs can be identified by analyzing reads from high-throughput deep sequencing. The reads realigned to miRNA precursors besides canonical miRNAs were initially considered as sequencing noise and ignored from further analysis. Here we reported a small-RNA species of phased and half-phased miRNA-like RNAs different from canonical miRNAs from cassava miRNA precursors detected under four distinct chilling conditions. They can form abundant multiple small RNAs arranged along precursors in a tandem and phased or half-phased fashion. Some of these miRNA-like RNAs were experimentally confirmed by re-amplification and re-sequencing, and have a similar qRT-PCR detection ratio as their cognate canonical miRNAs. The target genes of those phased and half-phased miRNA-like RNAs function in process of cell growth metabolism and play roles in protein kinase. Half-phased miR171d.3 was confirmed to have cleavage activities on its target gene P-glycoprotein 11, a broad substrate efflux pump across cellular membranes, which is thought to provide protection for tropical cassava during sharp temperature decease. Our results showed that the RNAs from miRNA precursors are miRNA-like small RNAs that are viable negative gene regulators and may have potential functions in cassava chilling responses
Supervised Sparsity Preserving Projections for Face Recognition
Recently feature extraction methods have commonly been used as a principled approach to understand the intrinsic structure hidden in high-dimensional data. In this paper, a novel supervised learning method, called Supervised Sparsity Preserving Projections (SSPP), is proposed. SSPP attempts to preserve the sparse representation structure of the data when identifying an efficient discriminant subspace. First, SSPP creates a concatenated dictionary by class-wise PCA decompositions and learns the sparse representation structure of each sample under the constructed dictionary using the least squares method. Second, by maximizing the ratio of non-local scatter to local scatter, a Laplacian discriminant function is defined to characterize the separability of the samples in the different sub-manifolds. Then, to achieve improved recognition results, SSPP integrates the learned sparse representation structure as a regular term into the Laplacian discriminant function. Finally, the proposed method is converted into a generalized eigenvalue problem. The extensive and promising experimental results on several popular face databases validate the feasibility and effectiveness of the proposed approach
Physically Interpretable Feature Learning and Inverse Design of Supercritical Airfoils
Machine-learning models have demonstrated a great ability to learn complex
patterns and make predictions. In high-dimensional nonlinear problems of fluid
dynamics, data representation often greatly affects the performance and
interpretability of machine learning algorithms. With the increasing
application of machine learning in fluid dynamics studies, the need for
physically explainable models continues to grow. This paper proposes a feature
learning algorithm based on variational autoencoders, which is able to assign
physical features to some latent variables of the variational autoencoder. In
addition, it is theoretically proved that the remaining latent variables are
independent of the physical features. The proposed algorithm is trained to
include shock wave features in its latent variables for the reconstruction of
supercritical pressure distributions. The reconstruction accuracy and physical
interpretability are also compared with those of other variational
autoencoders. Then, the proposed algorithm is used for the inverse design of
supercritical airfoils, which enables the generation of airfoil geometries
based on physical features rather than the complete pressure distributions. It
also demonstrates the ability to manipulate certain pressure distribution
features of the airfoil without changing the others
Study of transfer learning from 2D supercritical airfoils to 3D transonic swept wings
Machine learning has been widely utilized in fluid mechanics studies and
aerodynamic optimizations. However, most applications, especially flow field
modeling and inverse design, involve two-dimensional flows and geometries. The
dimensionality of three-dimensional problems is so high that it is too
difficult and expensive to prepare sufficient samples. Therefore, transfer
learning has become a promising approach to reuse well-trained two-dimensional
models and greatly reduce the need for samples for three-dimensional problems.
This paper proposes to reuse the baseline models trained on supercritical
airfoils to predict finite-span swept supercritical wings, where the simple
swept theory is embedded to improve the prediction accuracy. Two baseline
models for transfer learning are investigated: one is commonly referred to as
the forward problem of predicting the pressure coefficient distribution based
on the geometry, and the other is the inverse problem that predicts the
geometry based on the pressure coefficient distribution. Two transfer learning
strategies are compared for both baseline models. The transferred models are
then tested on the prediction of complete wings. The results show that transfer
learning requires only approximately 500 wing samples to achieve good
prediction accuracy on different wing planforms and different free stream
conditions. Compared to the two baseline models, the transferred models reduce
the prediction error by 60% and 80%, respectively
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