244 research outputs found
Effect of polymer on disproportionate permeability reduction to gas and water for fractured shales
Large volumes of fracturing fluid are required in shale slickwater fracs, and a considerable amount of polymer friction reducer would remain in microfractures if the polymer has not been broken before gas production. It is of major interest to evaluate the effect of polymer on water/gas flow behavior in the microfractures of shale reservoirs. We fabricated six shale fracture models with different fracture widths and set up a core flooding apparatus to conduct brine/gas-injection experiments before and after polymer treatment. A method by which to calculate the residual resistance factor for gas (Frr,gas) was defined. The experimental results illustrate that polymer can reduce the permeability to water more than to gas. In the first cycle of brine/gas injection experiments after polymer treatment, the residual resistance factor for brine (Frr,water) and Frr,gas exhibited power-law characteristics through their shear rate and superficial gas velocity, respectively. The Frr,water and Frr,gas tended to decrease as the fracture width grew. Surprisingly, the Frr,gas was less than one in larger fractures in which Frr,gas tended to stabilize after polymer treatment, which indicates that polymer treatment does not impair gas flow in wider fractures, and may even improve it. The mechanisms responsible for disproportionate permeability reduction (DPR) in the fractured shales were proposed in this paper. --Abstract, page iii
DISC: Deep Image Saliency Computing via Progressive Representation Learning
Salient object detection increasingly receives attention as an important
component or step in several pattern recognition and image processing tasks.
Although a variety of powerful saliency models have been intensively proposed,
they usually involve heavy feature (or model) engineering based on priors (or
assumptions) about the properties of objects and backgrounds. Inspired by the
effectiveness of recently developed feature learning, we provide a novel Deep
Image Saliency Computing (DISC) framework for fine-grained image saliency
computing. In particular, we model the image saliency from both the coarse- and
fine-level observations, and utilize the deep convolutional neural network
(CNN) to learn the saliency representation in a progressive manner.
Specifically, our saliency model is built upon two stacked CNNs. The first CNN
generates a coarse-level saliency map by taking the overall image as the input,
roughly identifying saliency regions in the global context. Furthermore, we
integrate superpixel-based local context information in the first CNN to refine
the coarse-level saliency map. Guided by the coarse saliency map, the second
CNN focuses on the local context to produce fine-grained and accurate saliency
map while preserving object details. For a testing image, the two CNNs
collaboratively conduct the saliency computing in one shot. Our DISC framework
is capable of uniformly highlighting the objects-of-interest from complex
background while preserving well object details. Extensive experiments on
several standard benchmarks suggest that DISC outperforms other
state-of-the-art methods and it also generalizes well across datasets without
additional training. The executable version of DISC is available online:
http://vision.sysu.edu.cn/projects/DISC.Comment: This manuscript is the accepted version for IEEE Transactions on
Neural Networks and Learning Systems (T-NNLS), 201
Road Network Guided Fine-Grained Urban Traffic Flow Inference
Accurate inference of fine-grained traffic flow from coarse-grained one is an
emerging yet crucial problem, which can help greatly reduce the number of
traffic monitoring sensors for cost savings. In this work, we notice that
traffic flow has a high correlation with road network, which was either
completely ignored or simply treated as an external factor in previous works.
To facilitate this problem, we propose a novel Road-Aware Traffic Flow
Magnifier (RATFM) that explicitly exploits the prior knowledge of road networks
to fully learn the road-aware spatial distribution of fine-grained traffic
flow. Specifically, a multi-directional 1D convolutional layer is first
introduced to extract the semantic feature of the road network. Subsequently,
we incorporate the road network feature and coarse-grained flow feature to
regularize the short-range spatial distribution modeling of road-relative
traffic flow. Furthermore, we take the road network feature as a query to
capture the long-range spatial distribution of traffic flow with a transformer
architecture. Benefiting from the road-aware inference mechanism, our method
can generate high-quality fine-grained traffic flow maps. Extensive experiments
on three real-world datasets show that the proposed RATFM outperforms
state-of-the-art models under various scenarios
Three dimensional photonic Dirac points in metamaterials
Topological semimetals, representing a new topological phase that lacks a
full bandgap in bulk states and exhibiting nontrivial topological orders,
recently have been extended to photonic systems, predominantly in photonic
crystals and to a lesser extent, metamaterials. Photonic crystal realizations
of Dirac degeneracies are protected by various space symmetries, where Bloch
modes span the spin and orbital subspaces. Here, we theoretically show that
Dirac points can also be realized in effective media through the intrinsic
degrees of freedom in electromagnetism under electromagnetic duality. A pair of
spin polarized Fermi arc like surface states is observed at the interface
between air and the Dirac metamaterials. These surface states show linear
k-space dispersion relation, resulting in nearly diffraction-less propagation.
Furthermore, eigen reflection fields show the decomposition from a Dirac point
to two Weyl points. We also find the topological correlation between a Dirac
point and vortex/vector beams in classic photonics. The theoretical proposal of
photonic Dirac point lays foundation for unveiling the connection between
intrinsic physics and global topology in electromagnetism.Comment: 15 pages, 5 figure
STEERER: Resolving Scale Variations for Counting and Localization via Selective Inheritance Learning
Scale variation is a deep-rooted problem in object counting, which has not
been effectively addressed by existing scale-aware algorithms. An important
factor is that they typically involve cooperative learning across
multi-resolutions, which could be suboptimal for learning the most
discriminative features from each scale. In this paper, we propose a novel
method termed STEERER (\textbf{S}elec\textbf{T}iv\textbf{E}
inh\textbf{ER}itance l\textbf{E}a\textbf{R}ning) that addresses the issue of
scale variations in object counting. STEERER selects the most suitable scale
for patch objects to boost feature extraction and only inherits discriminative
features from lower to higher resolution progressively. The main insights of
STEERER are a dedicated Feature Selection and Inheritance Adaptor (FSIA), which
selectively forwards scale-customized features at each scale, and a Masked
Selection and Inheritance Loss (MSIL) that helps to achieve high-quality
density maps across all scales. Our experimental results on nine datasets with
counting and localization tasks demonstrate the unprecedented scale
generalization ability of STEERER. Code is available at
\url{https://github.com/taohan10200/STEERER}.Comment: Accepted by ICCV2023, 9 page
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