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Recent progress on the jetting of single deformed cavitation bubbles near boundaries

Journal of Hydrodynamics 2023年第5期35卷 832-857页

作者： Jing-zhu Wang Guang-hang Wang Qing-yun Zeng yi-wei Wang Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing100190China School of Engineering Science University of the Chinese Academy of SciencesBeijing100049China School of Future Technology University of the Chinese Academy of SciencesBeijing100049China College of Shipbuilding Engineering Harbin Engineering UniversityHarbin150001China Nanhai Institute of Harbin Engineering University Sanya572024China Guangdong Aerospace Research Academy Guangzhou511458China

Cavitation occurs widely in nature and engineering and is a complex problem with multiscale features in both time and space due to its associating violent oscillations. To understand the important but complicated phenomena and fluid mechanics behind cavitation, a great deal of effort has been invested in investigating the collapse of a single bubble near different boundaries. This review aims to cover recent developments in the collapse of single bubbles in the vicinity of complex boundaries, including single boundaries and two parallel boundaries, and open questions for future research are discussed. Microjets are the most prominent features of the non-spherical collapse of cavitation bubbles near boundaries and are directed toward rigid walls and away from free surfaces. Such a bubble generally splits, resulting in the formation of two axial jets directed opposite to each other under the constraints of an elastic boundary or two parallel boundaries. The liquid jet penetrates the bubble, impacts the boundary, and exerts a great deal of stress on any nearby boundary. This phenomenon can cause damage, such as the erosion of blades in hydraulic machinery, the rupture of human blood vessels, and underwater explosions, but can also be exploited for applications, such as needle-free injection, drug and gene delivery, surface cleaning, and printing. Many fascinating developments related to these topics are presented and summarized in this review. Finally, three directions are proposed that seem particularly fruitful for future research on the interaction of cavitation bubbles and boundaries.

关键词： Jetting cavitation bubble near complex boundaries bubble-based technique and their applications

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Singularity radius gradient-based rapid singularity-escape steering law for SGCMGs

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Chinese Journal of Aeronautics 2020年第10期33卷 2728-2742页

作者： Tao yi Yunhai GENG Baolin wu Research Center of Satellite Technology Harbin Institute of TechnologyHarbin 150080China

In order to visualize singularity of SGCMGs in gimbal angle space,a novel continuous bounded singularity parameter--Singularity Radius,whose sign can distinctly determine singularity type,is *** a rapid singularity-escape steering law is proposed basing on gradient of Singularity Radius and residual base vector to drive the SGCMG system to neighboring singular boundary,and quickly escape elliptic ***,simulation results on Pyramid-type and skew-type configuration demonstrate the effectiveness and rapidness of the proposed steering law.

关键词： Gaussian curvature Rapid singularity escape Single gimbal control moment gyroscope Singularity-escape steering law Singularity parameter Singularity type

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The influence of prostate volume on cancer detection in the Chinese population

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Asian Journal of Andrology 2014年第3期16卷 482-486页

作者： yi-Shuo wu Department of Urology Huashan Hospital Shanghai Urology Research Center Fudan University Shanghai China Center for Cancer Genomics Wake Forest University School of Medicine Winston-Salem North Carolina USA

In western populations, prostate volume （PV） has been proven to be one of the strongest predictors of detecting prostate cancer （PCa） in biopsies. We performed this study in a biopsy cohort, to evaluate associations among the prostate volume, prostate-specific antigen （PSA） and PCa detection in the Chinese population. Between the years, 2007-13, 1486 men underwent prostate biopsy at Huashan Hospital, Fudan University, Shanghai, China. The study population was divided into two groups for analysis according to total PSA （tPSA） range （4 ng m1-1 〈tPSA 〈20 ng m1-1 and tPSA 〉20 ng ml-1）. PV, age, tPSA, digital rectal examination （DRE） and transrectal ultrasound （TRUS） results were also included in the analysis. Although the positive biopsy rates decreased in both tPSA range groups, the downtrend was more pronounced in the 4 ng ml-2 〈tPSA 〈20 ng m1-1 group; therefore, we focused on 853 men in this group with increasing PV. In multivariate logistic regression analysis, only DRE was found to be associated with PCa in four PV groups （P 〈 0.05） and tPSA did not show a good predictive ability when PV exceeded 50 ml （P 〉 0.05）. Further, it may suggest that with increasing PV, the cancer detection rate decreased in men with different tPSA, DRE and TRUS nodule statuses （all P values for trends were 〈0.001）. Our study indicates that in tPSA ranging from 4 to 20 ng ml-1, the use of PV ranges of 0-35 ml, 35-50 ml and 〉50 ml might be taken into consideration for the biopsy decision-making in the Chinese population.

关键词： China prostate cancer prostate-specific antigen prostate volume

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Frequency-dependent random fatigue of panel-type structures made of ceramic matrix composites

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Acta Mechanica Solida Sinica 2017年第2期30卷 165-173页

作者： Yadong Zhou Xiaochen hang Shaoqing wu Qingguo Fei Natasa Trisovic Department of Engineering Mechanics Southeast University Nanjing 210096 PR China Department of Civil and Environmental Engineering and Department of Mechanical Engineering NorthwesternUniversity Evanston IL 60208 USA Department of Aerospace Engineering and Mechanics University of Alabama Tuscaloosa AL 35487 USA School of Mechanical Engineering Southeast University Nanjing 210096 PR China Faculty of Mechanical Engineering Department of Mechanics University of Belgrade Belgrade 11120 Serbia

The panel-type structures used in aerospace engineering can be subjected to severe highfrequency acoustic loadings in service. This paper evaluates the frequency-dependent random fatigue of panel-type structures made of ceramic matrix composites（CMCs） under acoustic loadings. Firstly, the high-frequency random responses from the broadband random excitation will result in more stress cycles in a deinite period of time. The probability density distributions of stress amplitudes will be different in different frequency bandwidths, though the peak stress estimations are identical. Secondly, the fatigue properties of CMCs can be highly frequency-dependent. The fatigue evaluation method for the random vibration case is adopted to evaluate the fatigue damage of a representative stiffened panel structure. The frequency effect through S-N curves on random fatigue damage is numerically veriied. Finally, a parameter is demonstrated to characterize the mean vibration frequency of a random process, and hence this parameter can further be considered as a reasonable loading frequency in the fatigue tests of CMCs to obtain more reliable S-N ***, the inluence of vibration frequency can be incorporated in the random fatigue model from the two perspectives.

关键词： Random fatigue Frequency effect Ceramic matrix composites(CMCs) S-N curve Loading frequency

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A brief review of integrated and passive photonic reservoir computing systems and an approach for achieving extra non-linearity in passive devices

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Science China(Information Sciences) 2020年第6期63卷 97-104页

作者： Dachuan wu Yasha yi Yuxiao Zhang Integrated Nano Optoelectronics Laboratory Department of Electrical and Computer Engineering University of Michigan Energy Institute University of Michigan

Photonic-based reservoir computing(RC) systems have attracted significant attention. Integrated and purely passive systems are compatible with complementary metal-oxide-semiconductor devices,but are limited by the lack of non-linear components. This study consists of two parts: firstly, a review on the published integrated and passive RC system is presented. The review focuses on the structural configuration(rather than the mathematical model) of the neural network; secondly, a new approach for achieving an integrated and passive photonic RC system is introduced and discussed. This approach employs a mode combiner in front of the reservoir to achieve an extra non-linearity in a purely passive device. Moreover,the approach is numerically investigated, and an XOR(exclusive or) task is used to test the device, and the result shows that the new approach satisfies the requirement of an RC system.

关键词： reservoir computing integrated photonics neural network non-linearity

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Joint user profiling with hierarchical attention networks

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Frontiers of Computer Science 2023年第3期17卷 133-143页

作者： Xiaojian LIU yi ZHU Xindong wu Key Laboratory of Knowledge Engineering with Big Data(Hefei University of Technology) Ministry of EducationHefei 230009China School of Computer Science and Information Engineering Hefei University of TechnologyHefei 230009China School of Information Engineering Yangzhou UniversityYangzhou 225009China Mininglamp Academy of Sciences MininglampBeijing 100193China

User profiling by inferring user personality traits,such as age and gender,plays an increasingly important role in many real-world *** existing methods for user profiling either use only one type of data or ignore handling the noisy information of ***,they usually consider this problem from only one *** this paper,we propose a joint user profiling model with hierarchical attention networks(JUHA)to learn informative user representations for user *** JUHA method does user profiling based on both inner-user and inter-user *** explore inner-user features from user behaviors(e.g.,purchased items and posted blogs),and inter-user features from a user-user graph(where similar users could be connected to each other).JUHA learns basic sentence and bag representations from multiple separate sources of data(user behaviors)as the first round of data *** this module,convolutional neural networks(CNNs)are introduced to capture word and sentence features of age and gender while the self-attention mechanism is exploited to weaken the noisy *** this,we build another bag which contains a user-user ***-user features are learned from this bag using propagation information between linked users in the *** acquire more robust data,inter-user features and other inner-user bag representations are joined into each sentence in the current bag to learn the final bag ***,all of the bag representations are integrated to lean comprehensive user representation by the self-attention *** experimental results demonstrate that our approach outperforms several state-of-the-art methods and improves prediction performance.

关键词： user profiling hierarchical attention joint learning inner-user feature inter-user feature

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Two-dimensional semiconductor heterostructures for photocatalytic CO_(2)conversion

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Science China Chemistry 2024年第8期67卷 2434-2447页

作者： Yang wu Mingyu wu Yongfu Sun yi Xie Hefei National Research Center for Physical Sciences at Microscale University of Science and Technology of ChinaHefei 230026China

The CO_(2)reduction into carbon-contained fuel via solar energy offers the powerful tools to realize the zero-emission carbon *** to the intriguing features of the two-dimensional(2D)heterostructures,it is susceptible to modulate the electronic structure as well as the surface geometry for optimizing the photocatalytic CO_(2)*** this perspective,we surveyed the fundamental insights of 2D semiconductor heterostructures,involving the fabrication strategies and classification of the 2D semiconductor ***,we have detailly discussed the overview of 2D semiconductor heterostructure for optimizing CO_(2)photocatalytic influenced factors,including the solar energy utilization,photogenerated carriers separation,and redox reaction ***,we showed the significant advantages of 2D heterostructures in elevating CO_(2)photoreduction performance,focusing on activity,selectivity and *** analyzing the limitations and developments,we ended by putting forward insights into the further researches about the CO_(2)photocatalysts and reactor design,even industrial applications.

关键词： two-dimensional semiconductor heterostructures photocatalysis CO_(2)conversion

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Parameter estimation in exponential models by linear and nonlinear fitting methods

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Frontiers of Information Technology & Electronic Engineering 2017年第3期18卷 434-444页

作者： Ping YANG Chao-peng wu yi-lu GUO Hong-bo LIU Hui HUANG hang-zhou WANG Shu-yue ZHAN Bang-yi TAO Quan-quan MU Qiang WANG Hong SONG School of Digital Media & Design Hangzhou Dianzi University Ocean College Zhejiang University State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyState Oceanic Administration State Key Laboratory of Applied Optics Changchun Institute of OpticsFine Mechanics and PhysicsChinese Academy of Sciences

Estimation of unknown parameters in exponential models by linear and nonlinear fitting methods is discussed. Based on the extreme value theorem and Taylor series expansion, it is proved theoretically that the parameters estimated by the linear fitting method alone cannot minimize the sum of the squared residual errors in the measurement data when measurement noise is involved in the data. Numerical simulation is performed to compare the performance of the linear and nonlinear fitting methods. Simulation results show that the linear method can obtain only a suboptimal estimate of the unknown parameters and that the nonlinear method gives more accurate results. Application of the fitting methods is demonstrated where the water spectral attenuation coefficient is estimated from underwater images and imaging distances, which supports the improvement in the accuracy of parameter estimation by the nonlinear fitting method.

关键词： Exponential model Parameter estimation Linear least squares Nonlinear fitting

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Recent advances and key perspectives of in-situ studies for oxygen evolution reaction in water electrolysis

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Green Energy & Environment 2024年第10期9卷 1497-1517页

作者： yi Wang Zichen Xu Xianhong wu Zhong-Shuai wu State Key Laboratory of Catalysis Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian116023China University of Chinese Academy of Sciences Shijingshan DistrictBeijing100049China Dalian National Laboratory for Clean Energy Chinese Academy of SciencesDalian116023China

Electricity-driven water splitting to produce hydrogen is one of the most efficient ways to alleviate energy crisis and environmental pollution problems,in which the anodic oxygen evolution reaction(OER)is the key half-reaction of performance-limiting in water *** the complicated reaction process and surface reconstruction of the involved catalysts under actual working conditions,unraveling the real active sites,probing multiple reaction intermediates and clarifying catalytic pathways through in-situ characterization techniques and theoretical calculations are *** this review,we summarize the recent advancements in understanding the catalytic process,unlocking the water oxidation active phase and elucidating catalytic mechanism of water oxidation by various in-situ characterization ***,we introduce conventionally proposed traditional catalytic mechanisms and novel evolutionary mechanisms of OER,and highlight the significance of optimal catalytic pathways and intrinsic ***,we provide a comprehensive overview of the fundamental working principles,different detection modes,applicable scenarios,and limitations associated with the in-situ characterization ***,we exemplified the in-situ studies and discussed phase transition detection,visualization of speciation evolution,electronic structure tracking,observation of reaction active intermediates,and monitoring of catalytic products,as well as establishing catalytic structure-activity relationships and catalytic ***,the key challenges and future perspectives for demystifying the water oxidation process are briefly proposed.

关键词： In-situ studies Water splitting Oxygen evolution reaction Catalytic mechanism

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On Nonuniqueness of Geodesics and Geodesic Disks in the Universal Asymptotic Teichmüller Space

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Acta Mathematica Sinica,English Series 2017年第2期33卷 201-209页

作者： yi QI Yan wu LMIB and School of Mathematics and Systems Science Beihang University Beijing 100191 P. R. China School of Science Linyi University Linyi 276005 P. R. China

Abstract The non-uniqueness on geodesics and geodesic disks in the universal asymptotic Teichmfiller space AT（D） are studied in this paper. It is proved that if # is asymptotically extremal in [[#]] with h （μ）〈 h＊（μ） for some point ζ∈D, then there exist infinitely many geodesic segments joining [[0]] and [[μ]], and infinitely many holomorphic geodesic disks containing [[0]] and [μ]] in AT（D）.

关键词： Asymptotic Teichmuller space geodesics geodesic disks holomorphic isometry Teichmul-ler metric

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