66 research outputs found
Optimizing the thermal performance of building envelopes for energy saving in underground office buildings in various climates of China
This article investigates the influence of the thermal performance of building envelopes on annual energy consumption in a ground-buried office building by means of the dynamic building energy simulation, aiming at offering reasonable guidelines for the energy efficient design of envelopes for underground office buildings in China. In this study, the accuracy of dealing with the thermal process for underground buildings by using the Designer's Energy Simulation Tool (DeST) is validated by measured data. The analyzed results show that the annual energy consumptions for this type of buildings vary significantly, and it is based on the value of the overall heat transfer coefficient (U-value) of the envelopes. Thus, it is necessary to optimize the U-value for underground buildings located in various climatic zones in China. With respect to the roof, an improvement in its thermal performance is significantly beneficial to the underground office building in terms of annual energy demand. With respect to the external walls, the optimized U-values completely change with the distribution of the climate zones. The recommended optimal values for various climate zones of China are also specified as design references for public office building in underground in terms of the building energy efficiency
Learning Robust Medical Image Segmentation from Multi-source Annotations
Collecting annotations from multiple independent sources could mitigate the
impact of potential noises and biases from a single source, which is a common
practice in medical image segmentation. Learning segmentation networks from
multi-source annotations remains a challenge due to the uncertainties brought
by the variance of annotations and the quality of images. In this paper, we
propose an Uncertainty-guided Multi-source Annotation Network (UMA-Net), which
guides the training process by uncertainty estimation at both the pixel and the
image levels. First, we developed the annotation uncertainty estimation module
(AUEM) to learn the pixel-wise uncertainty of each annotation, which then
guided the network to learn from reliable pixels by weighted segmentation loss.
Second, a quality assessment module (QAM) was proposed to assess the
image-level quality of the input samples based on the former assessed
annotation uncertainties. Importantly, we introduced an auxiliary predictor to
learn from the low-quality samples instead of discarding them, which ensured
the preservation of their representation knowledge in the backbone without
directly accumulating errors within the primary predictor. Extensive
experiments demonstrated the effectiveness and feasibility of our proposed
UMA-Net on various datasets, including 2D chest X-ray segmentation, fundus
image segmentation, and 3D breast DCE-MRI segmentation
Scale-aware Super-resolution Network with Dual Affinity Learning for Lesion Segmentation from Medical Images
Convolutional Neural Networks (CNNs) have shown remarkable progress in
medical image segmentation. However, lesion segmentation remains a challenge to
state-of-the-art CNN-based algorithms due to the variance in scales and shapes.
On the one hand, tiny lesions are hard to be delineated precisely from the
medical images which are often of low resolutions. On the other hand,
segmenting large-size lesions requires large receptive fields, which
exacerbates the first challenge. In this paper, we present a scale-aware
super-resolution network to adaptively segment lesions of various sizes from
the low-resolution medical images. Our proposed network contains dual branches
to simultaneously conduct lesion mask super-resolution and lesion image
super-resolution. The image super-resolution branch will provide more detailed
features for the segmentation branch, i.e., the mask super-resolution branch,
for fine-grained segmentation. Meanwhile, we introduce scale-aware dilated
convolution blocks into the multi-task decoders to adaptively adjust the
receptive fields of the convolutional kernels according to the lesion sizes. To
guide the segmentation branch to learn from richer high-resolution features, we
propose a feature affinity module and a scale affinity module to enhance the
multi-task learning of the dual branches. On multiple challenging lesion
segmentation datasets, our proposed network achieved consistent improvements
compared to other state-of-the-art methods.Comment: Journal paper under review. 10 pages. The first two authors
contributed equall
Deep Omni-supervised Learning for Rib Fracture Detection from Chest Radiology Images
Deep learning (DL)-based rib fracture detection has shown promise of playing
an important role in preventing mortality and improving patient outcome.
Normally, developing DL-based object detection models requires huge amount of
bounding box annotation. However, annotating medical data is time-consuming and
expertise-demanding, making obtaining a large amount of fine-grained
annotations extremely infeasible. This poses pressing need of developing
label-efficient detection models to alleviate radiologists' labeling burden. To
tackle this challenge, the literature of object detection has witnessed an
increase of weakly-supervised and semi-supervised approaches, yet still lacks a
unified framework that leverages various forms of fully-labeled,
weakly-labeled, and unlabeled data. In this paper, we present a novel
omni-supervised object detection network, ORF-Netv2, to leverage as much
available supervision as possible. Specifically, a multi-branch omni-supervised
detection head is introduced with each branch trained with a specific type of
supervision. A co-training-based dynamic label assignment strategy is then
proposed to enable flexibly and robustly learning from the weakly-labeled and
unlabeled data. Extensively evaluation was conducted for the proposed framework
with three rib fracture datasets on both chest CT and X-ray. By leveraging all
forms of supervision, ORF-Netv2 achieves mAPs of 34.7, 44.7, and 19.4 on the
three datasets, respectively, surpassing the baseline detector which uses only
box annotations by mAP gains of 3.8, 4.8, and 5.0, respectively. Furthermore,
ORF-Netv2 consistently outperforms other competitive label-efficient methods
over various scenarios, showing a promising framework for label-efficient
fracture detection.Comment: 11 pages, 4 figures, and 7 table
Two-dimensional Massless Dirac Fermions in Antiferromagnetic AFe2As2 (A = Ba, Sr)
We report infrared studies of AFeAs (A = Ba, Sr), two
representative parent compounds of iron-arsenide superconductors, at magnetic
fields (B) up to 17.5 T. Optical transitions between Landau levels (LLs) were
observed in the antiferromagnetic states of these two parent compounds. Our
observation of a dependence of the LL transition energies, the
zero-energy intercepts at B = 0 T under the linear extrapolations of the
transition energies and the energy ratio ( 2.4) between the observed LL
transitions, combined with the linear band dispersions in two-dimensional (2D)
momentum space obtained by theoretical calculations, demonstrates the existence
of massless Dirac fermions in antiferromagnetic BaFeAs. More
importantly, the observed dominance of the zeroth-LL-related absorption
features and the calculated bands with extremely weak dispersions along the
momentum direction indicate that massless Dirac fermions in
BaFeAs are 2D. Furthermore, we find that the total substitution of
the barium atoms in BaFeAs by strontium atoms not only maintains 2D
massless Dirac fermions in this system, but also enhances their Fermi velocity,
which supports that the Dirac points in iron-arsenide parent compounds are
topologically protected.Comment: Magneto-infrared study, Landau level spectroscopy, DFT+DMFT
calculation
Pseudo Bias-Balanced Learning for Debiased Chest X-ray Classification
Deep learning models were frequently reported to learn from shortcuts like
dataset biases. As deep learning is playing an increasingly important role in
the modern healthcare system, it is of great need to combat shortcut learning
in medical data as well as develop unbiased and trustworthy models. In this
paper, we study the problem of developing debiased chest X-ray diagnosis models
from the biased training data without knowing exactly the bias labels. We start
with the observations that the imbalance of bias distribution is one of the key
reasons causing shortcut learning, and the dataset biases are preferred by the
model if they were easier to be learned than the intended features. Based on
these observations, we proposed a novel algorithm, pseudo bias-balanced
learning, which first captures and predicts per-sample bias labels via
generalized cross entropy loss and then trains a debiased model using pseudo
bias labels and bias-balanced softmax function. We constructed several chest
X-ray datasets with various dataset bias situations and demonstrated with
extensive experiments that our proposed method achieved consistent improvements
over other state-of-the-art approaches.Comment: To appear in MICCAI 2022. Code available at
https://github.com/LLYXC/PBB
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