379 research outputs found

    Fluorescence of CdSe/ZnS Quantum Dots in Toluene: Effect of Cyclic Temperature

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    Quantum dots (QDs) are the potential material for the application in optical thermometry, and have been successfully applied to solar cells, LEDs, bio-labeling, structural health monitoring, etc. In this paper, we study the fluorescence properties of CdSe/ZnS QDs in toluene under the action of heating-cooling cycles. The experimental results show that, in a heating-cooling cycle, increasing temperature causes red-shift of the emission peak and the decrease of the PL intensity, and decreasing temperature causes blue-shift of the emission peak and the increase of the PL intensity. The surface structures of the QDs likely are dependent on the cycle numbers, which cause the change of the excited energy state of the QDs in toluene. The results presented in this paper reveals the strong effects of cyclic temperature on the photoluminescence characteristics of QDs

    Toward Sufficient Spatial-Frequency Interaction for Gradient-aware Underwater Image Enhancement

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    Underwater images suffer from complex and diverse degradation, which inevitably affects the performance of underwater visual tasks. However, most existing learning-based Underwater image enhancement (UIE) methods mainly restore such degradations in the spatial domain, and rarely pay attention to the fourier frequency information. In this paper, we develop a novel UIE framework based on spatial-frequency interaction and gradient maps, namely SFGNet, which consists of two stages. Specifically, in the first stage, we propose a dense spatial-frequency fusion network (DSFFNet), mainly including our designed dense fourier fusion block and dense spatial fusion block, achieving sufficient spatial-frequency interaction by cross connections between these two blocks. In the second stage, we propose a gradient-aware corrector (GAC) to further enhance perceptual details and geometric structures of images by gradient map. Experimental results on two real-world underwater image datasets show that our approach can successfully enhance underwater images, and achieves competitive performance in visual quality improvement

    Geometry-based spherical JND modeling for 360∘^\circ display

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    360∘^\circ videos have received widespread attention due to its realistic and immersive experiences for users. To date, how to accurately model the user perceptions on 360∘^\circ display is still a challenging issue. In this paper, we exploit the visual characteristics of 360∘^\circ projection and display and extend the popular just noticeable difference (JND) model to spherical JND (SJND). First, we propose a quantitative 2D-JND model by jointly considering spatial contrast sensitivity, luminance adaptation and texture masking effect. In particular, our model introduces an entropy-based region classification and utilizes different parameters for different types of regions for better modeling performance. Second, we extend our 2D-JND model to SJND by jointly exploiting latitude projection and field of view during 360∘^\circ display. With this operation, SJND reflects both the characteristics of human vision system and the 360∘^\circ display. Third, our SJND model is more consistent with user perceptions during subjective test and also shows more tolerance in distortions with fewer bit rates during 360∘^\circ video compression. To further examine the effectiveness of our SJND model, we embed it in Versatile Video Coding (VVC) compression. Compared with the state-of-the-arts, our SJND-VVC framework significantly reduced the bit rate with negligible loss in visual quality

    Shakedown, ratcheting and fatigue analysis of cathode coating in lithium-ion battery under steady charging-discharging process

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    The cyclic plasticity behaviour and failure mechanism of the cathode material in lithium-ion batteries urgently need to be understood due to the cyclic lithium-ion diffusion-induced stress during charging-discharging process. Many researches have focused on the shakedown and ratcheting responses of lithium-ion battery anode. However, the systematic investigation on the plasticity behaviour of lithium-ion battery cathode is still lacking. In this paper, the cyclic plasticity behaviour of LiNixMnyCozO2 electrode subjected to cyclic lithiation/delithiation under a constant mechanical load is investigated comprehensively. The shakedown, ratcheting and fatigue analyses of active layer are conducted using direct numerical techniques based on the Linear Matching Method framework, while coin cell electrochemical experiments are performed simultaneously to support the analysis. The effect of thickness of coating on the shakedown and ratcheting response is investigated, and the thickness is confirmed as a crucial parameter that can influence the battery performance. The strain-fatigue life curve is also obtained to effectively predict the life of active coating. Moreover, the numerical results reveal the existence of low cycle fatigue at the centre, and ratcheting mechanism on the edge of the cathode, which is consistent well with the experimental result

    Opening CALASYS to All Members

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    Since the Chinese American Librarians Association’s Academic Resources and Repository System (CALASYS, https://ir.cala-web.org/) was initiated in 2013, its collections have grown gradually by way of the Committee’s curation and entries with occasional help from LIS students. In order to resolve the bottleneck problems, promote CALASYS and expand its content, the 2020-2021 CALASYS Committee has strongly pursued the idea of opening CALASYS to all of the CALA members. The Committee began to implement the author self-contribution plug-in in the CALASYS’ Omeka platform in 2020. This poster will focus on the implementation of the self-contribution plug-in. It will cover the main steps and tasks of the implementation, including making metadata contribution templates, selecting copyright options, establishing contributor verification, testing workflow and developing end-user guide and back-end management documentations. It will also address the Committee’s work on creating training materials on workflow and metadata and plans on providing training sessions online to the CALA community. It will include the CALASYS’ history, its main features, collections, and usage statistics as well. By opening CALASYS to all members, it is hoped that it will better achieve the CALA’s strategic plan of 2020-2025, “Make CALA’s impact on local, state, national, and international levels.” Meanwhile, the bottleneck problems will be resolved and CALASYS will continue to grow at a faster pace in a more inclusive direction. The accompanying video is also available at: https://youtu.be/q9g4SXsnuO0

    Saliency-Aware Spatio-Temporal Artifact Detection for Compressed Video Quality Assessment

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    Compressed videos often exhibit visually annoying artifacts, known as Perceivable Encoding Artifacts (PEAs), which dramatically degrade video visual quality. Subjective and objective measures capable of identifying and quantifying various types of PEAs are critical in improving visual quality. In this paper, we investigate the influence of four spatial PEAs (i.e. blurring, blocking, bleeding, and ringing) and two temporal PEAs (i.e. flickering and floating) on video quality. For spatial artifacts, we propose a visual saliency model with a low computational cost and higher consistency with human visual perception. In terms of temporal artifacts, self-attention based TimeSFormer is improved to detect temporal artifacts. Based on the six types of PEAs, a quality metric called Saliency-Aware Spatio-Temporal Artifacts Measurement (SSTAM) is proposed. Experimental results demonstrate that the proposed method outperforms state-of-the-art metrics. We believe that SSTAM will be beneficial for optimizing video coding techniques

    Growth and New Directions: CALA Academic Resources and Repository System

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    The Chinese American Librarians Association’s Academic Resources & Repository System (CALASYS) was established in 2013 and has been growing gradually ever since. To seek sustainable and greater growth in the future, the CALASYS 2019-2020 Committee reviewed previous efforts and explored new potentials in the repository’s content development, interface and functionality improvement and community engagement. This presentation will cover several issues that the Committee has addressed since its forming: developing new content for CALASYS such as a new top-level collection called ”Chinese Culture Heritage & Chinese Studies” and its children collections including the CALA Best Book Award Collection; starting or resuming testing on several Omeka plugins whose implementation would enhance the system’s functionality and performance significantly, such as Exhibit Builder, User Profile, Search by Metadata, CSS Editor and Geolocation; exploring other Omeka instances’ interfaces and improving the CALASYS’ appearance and presentation. This poster will also cover the continuing development of the CALA Archives, CALA Chapter Collections and CALA Member Scholarly Achievements collection, metadata editing and enhancement, statistics and usage of the repository, as well as involving students and CALA members in working with the repository. To develop an organization’s institutional repository is a long-term task, this presentation will conclude with a discussion of the lessons learned and strategies and tips on working with the repository for the committee members and the community
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