Spatiotemporal Saliency Detection Based on Superpixel-level Trajectory

International audienceIn this paper, we propose a novel spatiotemporal saliency model based on superpixel-level trajectories for saliency detection in videos. The input video is first decomposed into a set of temporally consistent superpixels, on which superpixel-level trajectories are directly generated, and motion histograms at superpixel level as well as frame level are extracted. Based on motion vector fields of multiple successive frames, the inside–outside maps are estimated to roughly indicate whether pixels are inside or outside objects with motion different from background. Then two descriptors, i.e. accumulated motion histogram and trajectory velocity entropy, are exploited to characterize the short-term and long-term temporal features of superpixel-level trajectories. Based on trajectory descriptors and inside–outside maps, superpixel-level trajectory distinctiveness is evaluated and trajectory classification is performed to obtain trajectory-level temporal saliency. Superpixel-level and pixel-level temporal saliency maps are generated in turn by exploiting motion similarity with neighboring superpixels around each trajectory, and color-spatial similarity with neighboring superpixels around each pixel, respectively. Finally, a quality-guided fusion method is proposed to integrate the pixel-level temporal saliency map with the pixel-level spatial saliency map, which is generated based on global contrast and spatial sparsity of superpixels, to generate the pixel-level spatiotemporal saliency map with reasonable quality. Experimental results on two public video datasets demonstrate that the proposed model outperforms the state-of-the-art spatiotemporal saliency models on saliency detection performance

Optimization Milling Force and Surface Roughness of Ti-6Al-4V Based on Ultrasonic-Assisted Milling (UAM): An Experimental Study

This study aimed to develop a longitudinal ultrasonic-assisted milling system to investigate the machinability of titanium (Ti) Alloy Ti-6Al-4V (TC4). Aiming at reduced milling force and enhanced surface quality, ultrasonic-assisted milling was investigated taking into account the following processing parameters: spindle speed (cutting rate) n, feed per tooth fz, milling depth ap, and ultrasonic amplitude A. A comparison was made with conventional milling. The results of univariate tests demonstrated that the ultrasonic amplitude had the most significant impact on the milling force along the z-axis, resulting in a reduction of 15.48% compared with conventional milling. The range analysis results of multivariate tests demonstrated that ap and fz were the dominant factors influencing the cutting force. The minimum reduction in the milling force in ultrasonic-assisted milling along the x-, y-, and z-axes was 11.77%, 15.52%, and 17.66%, respectively, compared with that in conventional milling. The ultrasonic-assisted milling led to reduced surface roughness and enhanced surface quality; the maximum surface roughness in ultrasonic-assisted milling was 25.93%, 36.36% and 26.32% in terms of n, fz, and ap, respectively. In longitudinal ultrasonic-assisted milling, the periodic “separation-contact” was accompanied by microimpacts, resulting in even smaller intermittent periodic cutting forces. Hence, regular fish scale machining mesh was observed on the processed surface, and the workpiece surface exhibited high cleanness and smoothness. The reasonable configuration of ultrasonic-assisted milling parameters can effectively improve the milling force and surface quality of Ti alloys and accumulate reference data for the subsequent machining process research

Size-controlled synthesis and morphology evolution of bismuth trifluoride nanocrystals via a novel solvent extraction route

Monodisperse orthorhombic-phase BiF3 nanocrystals with various shapes were prepared easily by a novel solvent extraction approach using an acid-base-coupled extractant. More importantly, the extractant used in this route can be recycled after synthesis. Our results show great promise for further extending the method to the preparation of other metal-fluoride nanoparticles

Density functional investigation on cathode/electrolyte interface in solid-state lithium batteries

锂离子电池的广泛应用对储能器件的能量密度、安全性和充放电速度提出了新的要求. 全固态锂电池与传统锂离子电池相比具有更少的副反应和更高的安全性，已成为下一代储能器件的首选. 构建匹配的电极/电解质界面是在全固态锂电池中获得优异综合性能的关键. 本文采用第一性原理计算研究了固态电池中电解质表面及正极/电解质界面的局域结构和锂离子输运性质. 选取β-Li3PS4 (010)/LiCoO2 (104)和 Li4GeS4 (010)/LiCoO2 (104)体系计算了界面处的成键情况及锂离子的迁移势垒. 部分脱锂态的正极/电解质界面上由于Co-S成键的加强削弱了P/Ge-S键的强度，降低了对Li+的束缚，从而导致了更低的锂离子迁移势垒. 理解界面局域结构及其对Li+输运性质的影响将有助于我们在固态电池中构建性能优异的电极/电解质界面.The rapidly expanding application of lithium ion batteries stimulates research interest on energy storage devices with higher energy density, better safety and faster charge/discharge speed. All-solid-state lithium batteries have been considered as promising candidates because of their fewer side reactions and better safety compared with conventional lithium-ion batteries with organic liquid electrolytes. Looking for well-matched electrode/electrolyte interfaces is one of the keys to ensuring good comprehensive performance of solid-state lithium batteries. In this report, with the aid of first-principles simulations, the local structure and lithium ions transportation properties of electrolyte surfaces and cathode/electrolyte interfaces are investigated. The β-Li3PS4 (010)/LiCoO2 (104) and Li4GeS4(010)/LiCoO2(104) interfaces are adopted as model systems to understand the bonding interaction and Li+ migration barriers at interfaces. The ability of Li+ motion is improved in partial delithiated state for both systems, due to that Co atoms at the interface in high oxidized state oxidize the S atoms nearby and weaken the P/Ge-S bond resulting in less constrains on Li ions in neighbor and promoting the exchange of Li ions across the interface. It provides information for cathode/electrolyte interface optimization, and may help us discover appropriate techniques for solid-state lithium batteries.This work was supported by the National Natural Science Foundation of China (Grants No. 11234013), “863” Project (Grant No. 2015AA034201), Beijing S&T Project (Grant No. D161100002416003), and Youth Innovation Promotion Association (Grant No.2016005) for financial support and the Shanghai Supercomputer Center for providing computing resources.This work was supported by the National Natural Science Foundation of China (Grants No. 11234013), “863” Project (Grant No. 2015AA034201), Beijing S&T Project (Grant No. D161100002416003), and Youth Innovation Promotion Association (Grant No.2016005) for financial support and the Shanghai Supercomputer Center for providing computing resources.作者联系地址：1.北京凝聚态物理国家实验室，中国科学院物理研究所，北京，100190；2.电子科技大学能源科学与工程学院，成都，611731Author's Address: 1.Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; 2. School of Energy Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 611731通讯作者E-mail：[email protected]

Human Influenza A(H7N9) Virus Infection Associated with Poultry Farm, Northeastern China

We report on a case of human infection with influenza A(H7N9) virus in Jilin Province in northeastern China. This case was associated with a poultry farm rather than a live bird market, which may point to a new focus for public health surveillance and interventions in this evolving outbreak

T Cell Receptor-mediated Activation of CD4+CD44hi T Cells Bypasses Bcl10: AN IMPLICATION OF DIFFERENTIAL NF-κB DEPENDENCE OF NAïVE AND MEMORY T CELLS DURING T CELL RECEPTOR-MEDIATED RESPONSES*

Previous studies have demonstrated that Bcl10 (B-cell leukemia/lymphoma 10) is essential for T cell receptor-mediated NF-κB activation and subsequent proliferation and interleukin 2 (IL2) production. However, here we demonstrate that, contrary to expectations, Bcl10 is differentially required for T cell activation, including for both proliferation and cytokine production. When CD4+ and CD8+ T cells were divided based on expression levels of CD44, which distinguishes naïve cells (CD44lo) versus those that are antigen-experienced (CD44hi), IL2 production by and proliferation of CD4+CD44lo naïve cells and both subpopulations of CD8+ T cells were clearly Bcl10-dependent, whereas these same functional properties of CD4+CD44hi T cells occurred largely independent of Bcl10. As with the other subpopulations of T cells, CD4+CD44hi T cells did not activate the NF-κB pathway in the absence of Bcl10; nevertheless, these CD4+CD44hi antigen-experienced T cells efficiently secreted IL2 after T cell receptor stimulation. Strikingly, therefore, T cell receptor-mediated IL2 production in these cells is NF-κB-independent. Our studies suggest that antigen-experienced CD4+ T cells differ from their naïve counterparts and from CD8+ T cells in their ability to achieve activation independent of the Bcl10/NF-κB pathway