73 research outputs found
Vision Learners Meet Web Image-Text Pairs
Most recent self-supervised learning methods are pre-trained on the
well-curated ImageNet-1K dataset. In this work, given the excellent scalability
of web data, we consider self-supervised pre-training on noisy web sourced
image-text paired data. First, we conduct a benchmark study of representative
self-supervised pre-training methods on large-scale web data in a like-for-like
setting. We compare a range of methods, including single-modal ones that use
masked training objectives and multi-modal ones that use image-text
constrastive training. We observe that existing multi-modal methods do not
outperform their single-modal counterparts on vision transfer learning tasks.
We derive an information-theoretical view to explain these benchmark results,
which provides insight into how to design a novel vision learner. Inspired by
this insight, we present a new visual representation pre-training method,
MUlti-modal Generator~(MUG), that learns from scalable web sourced image-text
data. MUG achieves state-of-the-art transfer performance on a variety of tasks
and demonstrates promising scaling properties. Pre-trained models and code will
be made public upon acceptance.Comment: Project page: https://bzhao.me/MUG
Facile Synthesis of a 3,4-Ethylene-Dioxythiophene (EDOT) Derivative for Ease of Bio-Functionalization of the Conducting Polymer PEDOT
In the pursuit of conducting polymer based bio-functional devices, a cost-effective and high yield synthesis method for a versatile monomer is desired. We report here a new synthesis strategy for a versatile monomer 2-methylene-2,3-dihydrothieno (3,4-b) (1,4) dioxine, or 3,4-ethylenedioxythiophene with a exomethylene side group (EDOT-EM). Compared to the previously reported synthesis route, the new strategy uses less steps, with faster reaction rate, and higher yield. The presence of EM group opens up endless possibility for derivatization via either hydro-alkoxy addition or thiol-ene click chemistry. EDOT-EM could be polymerized into stable and low impedance PEDOT-EM polymer using electro-polymerization method on different conducting substrates at both macro and micro scales. Facile post-functionalization of PEDOT-EM with molecules of varying size and functionality (from small molecules to DNAs and proteins) was achieved. The new synthetic route of EDOT-EM and the ease of post-functionalization of PEDOT-EM will greatly accelerate the use of conducting polymer in a broad range of organic electronics and bioelectronics applications
Facile Synthesis of a 3,4-Ethylene-Dioxythiophene (EDOT) Derivative for Ease of Bio-Functionalization of the Conducting Polymer PEDOT
In the pursuit of conducting polymer based bio-functional devices, a cost-effective and high yield synthesis method for a versatile monomer is desired. We report here a new synthesis strategy for a versatile monomer 2-methylene-2,3-dihydrothieno (3,4-b) (1,4) dioxine, or 3,4-ethylenedioxythiophene with a exomethylene side group (EDOT-EM). Compared to the previously reported synthesis route, the new strategy uses less steps, with faster reaction rate, and higher yield. The presence of EM group opens up endless possibility for derivatization via either hydro-alkoxy addition or thiol-ene click chemistry. EDOT-EM could be polymerized into stable and low impedance PEDOT-EM polymer using electro-polymerization method on different conducting substrates at both macro and micro scales. Facile post-functionalization of PEDOT-EM with molecules of varying size and functionality (from small molecules to DNAs and proteins) was achieved. The new synthetic route of EDOT-EM and the ease of post-functionalization of PEDOT-EM will greatly accelerate the use of conducting polymer in a broad range of organic electronics and bioelectronics applications
SPHR-SAR-Net: Superpixel High-resolution SAR Imaging Network Based on Nonlocal Total Variation
High-resolution is a key trend in the development of synthetic aperture radar
(SAR), which enables the capture of fine details and accurate representation of
backscattering properties. However, traditional high-resolution SAR imaging
algorithms face several challenges. Firstly, these algorithms tend to focus on
local information, neglecting non-local information between different pixel
patches. Secondly, speckle is more pronounced and difficult to filter out in
high-resolution SAR images. Thirdly, the process of high-resolution SAR imaging
generally involves high time and computational complexity, making real-time
imaging difficult to achieve. To address these issues, we propose a Superpixel
High-Resolution SAR Imaging Network (SPHR-SAR-Net) for rapid despeckling in
high-resolution SAR mode. Based on the concept of superpixel techniques, we
initially combine non-convex and non-local total variation as compound
regularization. This approach more effectively despeckles and manages the
relationship between pixels while reducing bias effects caused by convex
constraints. Subsequently, we solve the compound regularization model using the
Alternating Direction Method of Multipliers (ADMM) algorithm and unfold it into
a Deep Unfolded Network (DUN). The network's parameters are adaptively learned
in a data-driven manner, and the learned network significantly increases
imaging speed. Additionally, the Deep Unfolded Network is compatible with
high-resolution imaging modes such as spotlight, staring spotlight, and sliding
spotlight. In this paper, we demonstrate the superiority of SPHR-SAR-Net
through experiments in both simulated and real SAR scenarios. The results
indicate that SPHR-SAR-Net can rapidly perform high-resolution SAR imaging from
raw echo data, producing accurate imaging results
A van der Waals pn heterojunction with organic/inorganic semiconductors
van der Waals (vdW) heterojunctions formed by two-dimensional (2D) materials
have attracted tremendous attention due to their excellent electrical/optical
properties and device applications. However, current 2D heterojunctions are
largely limited to atomic crystals, and hybrid organic/inorganic structures are
rarely explored. Here, we fabricate hybrid 2D heterostructures with p-type
dioctylbenzothienobenzothiophene (C8-BTBT) and n-type MoS2. We find that
few-layer C8-BTBT molecular crystals can be grown on monolayer MoS2 by vdW
epitaxy, with pristine interface and controllable thickness down to monolayer.
The operation of the C8-BTBT/MoS2 vertical heterojunction devices is highly
tunable by bias and gate voltages between three different regimes: interfacial
recombination, tunneling and blocking. The pn junction shows diode-like
behavior with rectifying ratio up to 105 at the room temperature. Our devices
also exhibit photovoltaic responses with power conversion efficiency of 0.31%
and photoresponsivity of 22mA/W. With wide material combinations, such hybrid
2D structures will offer possibilities for opto-electronic devices that are not
possible from individual constituents.Comment: 16 pages, 4 figure
Optimal configuration of energy storage considering flexibility requirements and operational risks in a power system
The integration of renewable energy units into power systems brings a huge challenge to the flexible regulation ability. As an efficient and convenient flexible resource, energy storage systems (ESSs) have the advantages of fast-response characteristics and bi-directional power conversion, which can provide flexible support for the power system. This paper establishes an optimization model for the ESS based on a bi-level programming model. The upper-level model optimizes the decision strategy of ESS configuration planning. The lower-level model is based on scenario analysis theory to simulate the operation of typical daily scenarios. Flexibility requirement constraints are added to characterize the required flexibility resources of the power system. In addition, the conditional value-at-risk (CVaR) is applied to characterize the risk of wind curtailment and load shedding during operation. To simplify the model, a set of association constraints is introduced to convert the original bi-level programming model into a direct-solvable single-level mixed-integer linear programming (MILP) model. Finally, the effectiveness of the proposed model is verified through case studies
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