331 research outputs found
Localized Dimension Growth in Random Network Coding: A Convolutional Approach
We propose an efficient Adaptive Random Convolutional Network Coding (ARCNC)
algorithm to address the issue of field size in random network coding. ARCNC
operates as a convolutional code, with the coefficients of local encoding
kernels chosen randomly over a small finite field. The lengths of local
encoding kernels increase with time until the global encoding kernel matrices
at related sink nodes all have full rank. Instead of estimating the necessary
field size a priori, ARCNC operates in a small finite field. It adapts to
unknown network topologies without prior knowledge, by locally incrementing the
dimensionality of the convolutional code. Because convolutional codes of
different constraint lengths can coexist in different portions of the network,
reductions in decoding delay and memory overheads can be achieved with ARCNC.
We show through analysis that this method performs no worse than random linear
network codes in general networks, and can provide significant gains in terms
of average decoding delay in combination networks.Comment: 7 pages, 1 figure, submitted to IEEE ISIT 201
Rotation and Confined Eruption of a Double Flux-Rope System
We perform a data-constrained simulation with the zero- assumption to
study the mechanisms of strong rotation and failed eruption of a filament in
active region 11474 on 2012 May 5 observed by Solar Dynamics Observatory and
Solar Terrestrial Relations Observatory. The initial magnetic field is provided
by nonlinear force-free field extrapolation, which is reconstructed by the
regularized Biot-Savart laws and magnetofrictional method. Our simulation
reproduces most observational features very well, e.g., the filament
large-angle rotation of about , the confined eruption and the
flare ribbons, allowing us to analyze the underlying physical processes behind
observations. We discover two flux ropes in the sigmoid system, an upper flux
rope (MFR1) and a lower flux rope (MFR2), which correspond to the filament and
hot channel in observations, respectively. Both flux ropes undergo confined
eruptions. MFR2 grows by tether-cutting reconnection during the eruption. The
rotation of MFR1 is related to the shear-field component along the axis. The
toroidal field tension force and the non-axisymmetry forces confine the
eruption of MFR1. We also suggest that the mutual interaction between MFR1 and
MFR2 contributes to the large-angle rotation and the eruption failure. In
addition, we calculate the temporal evolution of the twist and writhe of MFR1,
which is a hint of probable reversal rotation.Comment: 18 pages, 7 figures, Accepted for publication in Ap
Semi-Supervised Domain Generalization for Cardiac Magnetic Resonance Image Segmentation with High Quality Pseudo Labels
Developing a deep learning method for medical segmentation tasks heavily
relies on a large amount of labeled data. However, the annotations require
professional knowledge and are limited in number. Recently, semi-supervised
learning has demonstrated great potential in medical segmentation tasks. Most
existing methods related to cardiac magnetic resonance images only focus on
regular images with similar domains and high image quality. A semi-supervised
domain generalization method was developed in [2], which enhances the quality
of pseudo labels on varied datasets. In this paper, we follow the strategy in
[2] and present a domain generalization method for semi-supervised medical
segmentation. Our main goal is to improve the quality of pseudo labels under
extreme MRI Analysis with various domains. We perform Fourier transformation on
input images to learn low-level statistics and cross-domain information. Then
we feed the augmented images as input to the double cross pseudo supervision
networks to calculate the variance among pseudo labels. We evaluate our method
on the CMRxMotion dataset [1]. With only partially labeled data and without
domain labels, our approach consistently generates accurate segmentation
results of cardiac magnetic resonance images with different respiratory
motions. Code is available at: https://github.com/MAWanqin2002/STACOM2022MaComment: Accepted by International Workshop on Statistical Atlases and
Computational Models of the Heart (STACOM2022) of MICCAI202
Gadd45a promotes DNA demethylation through TDG
Growth arrest and DNA-damage-inducible protein 45 (Gadd45) family members have been implicated in DNA demethylation in vertebrates. However, it remained unclear how they contribute to the demethylation process. Here, we demonstrate that Gadd45a promotes active DNA demethylation through thymine DNA glycosylase (TDG) which has recently been shown to excise 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) generated in Ten-eleven-translocation (Tet)—initiated oxidative demethylation. The connection of Gadd45a with oxidative demethylation is evidenced by the enhanced activation of a methylated reporter gene in HEK293T cells expressing Gadd45a in combination with catalytically active TDG and Tet. Gadd45a interacts with TDG physically and increases the removal of 5fC and 5caC from genomic and transfected plasmid DNA by TDG. Knockout of both Gadd45a and Gadd45b from mouse ES cells leads to hypermethylation of specific genomic loci most of which are also targets of TDG and show 5fC enrichment in TDG-deficient cells. These observations indicate that the demethylation effect of Gadd45a is mediated by TDG activity. This finding thus unites Gadd45a with the recently defined Tet-initiated demethylation pathwa
Starling: An I/O-Efficient Disk-Resident Graph Index Framework for High-Dimensional Vector Similarity Search on Data Segment
High-dimensional vector similarity search (HVSS) is gaining prominence as a
powerful tool for various data science and AI applications. As vector data
scales up, in-memory indexes pose a significant challenge due to the
substantial increase in main memory requirements. A potential solution involves
leveraging disk-based implementation, which stores and searches vector data on
high-performance devices like NVMe SSDs. However, implementing HVSS for data
segments proves to be intricate in vector databases where a single machine
comprises multiple segments for system scalability. In this context, each
segment operates with limited memory and disk space, necessitating a delicate
balance between accuracy, efficiency, and space cost. Existing disk-based
methods fall short as they do not holistically address all these requirements
simultaneously. In this paper, we present Starling, an I/O-efficient
disk-resident graph index framework that optimizes data layout and search
strategy within the segment. It has two primary components: (1) a data layout
incorporating an in-memory navigation graph and a reordered disk-based graph
with enhanced locality, reducing the search path length and minimizing disk
bandwidth wastage; and (2) a block search strategy designed to minimize costly
disk I/O operations during vector query execution. Through extensive
experiments, we validate the effectiveness, efficiency, and scalability of
Starling. On a data segment with 2GB memory and 10GB disk capacity, Starling
can accommodate up to 33 million vectors in 128 dimensions, offering HVSS with
over 0.9 average precision and top-10 recall rate, and latency under 1
millisecond. The results showcase Starling's superior performance, exhibiting
43.9 higher throughput with 98% lower query latency compared to
state-of-the-art methods while maintaining the same level of accuracy.Comment: This paper has been accepted by SIGMOD 202
Evidence and impact of map error on land use and land cover dynamics in Ashi River watershed using intensity analysis
Abstract:Previously, applications of intensity analysis (IA) on land use and land cover change (LULCC) studies have focused on deviations from uniform intensity (UI) and failed to quantify the reasons behind these deviations. This study presents the application of IA with hypothetical errors that could explain non-uniform LULCC in the context of IA at four-time points. LULCC in the Ashi watershed was examined using Landsat images from 1990, 2000, 2010 and 2014 showing the classes: Urban, water, agriculture, close canopy, open canopy and other vegetation. Matrices were created to statistically examine LULCC using IA. The results reveal that the seeming LULCC intensities are not uniform with respect to the interval, category and transition levels of IA. Error analysis indicates that, hypothetical errors in 13%, 19% and 11.2% of the 2000, 2010 and 2014 maps respectively could account for all differences between the observed gain intensities and the UI; while errors in 12%, 21%, and 11% of the 1990, 2000 and 2010 maps respectively could account for all differences between the observed loss intensities and the UI. A hypothetical error in 0.6% and 1.6% of the 1990 map; 1.5% and 4% of the 2000 map; 1.2% and 2.1% of the 2010 map could explain divergences from uniform transitions given URB gain and AGR gain during 1990–2000, 2000–2010 and 2010–2014 respectively. Evidence for a specific deviation from the relevant hypothesized UI is either strong or weak depending on the size of these errors. We recommend that users of IA concept consider assessing their map errors, since limited ground information on past time point data exist. These errors will indicate strength of evidence for deviations and reveals patterns that increase researcher’s insight on LULCC processes
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