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A STUDY OF OSCILLATING FLOWS OVEr prOpAGATING rIppLES:pArT Ⅱ. VOrTICITY DYNAMICS

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Journal of Hydrodynamics 2000年第1期12卷 8-15页

作者： Lu xi yun Department of Modern Mechanics, univ.rsity of Science and Technology of china, Hefei 230026, p.r.china univ.of Science and Technology of China Hefei China

Vortex shedding for an oscillating flow over ripples is numerically investigated by solving 2 D time dependent incompressible Navier Stokes equations in curvilinear coordinates. The dynamics of vortex structures generated by flow separation is studied in order to understand some phenomena which take place near the bottom and in particular to get insight into the mechanism through which sediment grains are lifted up and maintained in suspension. Based on our calculated results, some important phenomena, such as vortex shedding, vortices pairing, vortices coalescence, vortex interaction with the free shear layer and so on, can be found. The behaviors of energy dissipation in the flow field and of shear stress along the ripple surface are also discussed for studying the dynamics of sediment grains in suspension and to obtain new information on the suspended load over the ripples.

关键词： oscillating flow ripple vorticity dynamics separation flow

A comparative study on mechanical and vibroacoustic performance of sandwich cylindrical shells with positive,negative,and zero poisson’s ratio cellular cores

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Journal of Ocean Engineering and Science 2024年第4期9卷 379-390页

作者： Qing Li peichang Li Yongjin Guo xi’an Liu State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai200240China china Ship Development and Design Center Wuhan430064China MOE Key Laboratory of Marine intelligent Equipment and System Shanghai Jiao Tong UniversityShanghai200240China

Deep-sea submersibles are significant mobile platforms requiring multi-functional capabilities that are strongly determined by the constituent *** cylindrical protective cover can be advanced by designing their sandwiched cellular materials whose physical properties can be readily parameterized and flexibly *** honeycomb materials are capable of possessing tuned positive,negative,or zero poisson’s ratios(ppr,Npr,and Zpr),which is expected to produce distinct physical performance when utilized as a cellular core of cylindrical shells for the deep-sea submersibles.A novel cylindrical meta-structure sandwiched with the semi-re-entrant Zpr metamaterial has been designed as well as its similarly-shaped sandwich cylindrical shell structures with ppr and Npr *** mechanical and vibroacoustic performance of sandwich cylindrical shells with cellular materials featuring a full characteristic range of poisson’s ratios are then compared systematically to explore their potential for engineering applications on submerged pressure-resistant *** respective unit cells are designed to feature an equivalent load-bearing *** properties of pressure resistance,buckling,and sound insulation are simulated,respectively,and the orders of each property are then generalized by systematic *** results indicate that the ppr honeycomb core takes advantage of higher structural strength and stability while the Zpr one yields better energy absorption and sound insulation *** Npr one yields moderate properties and has the potential for lower circumferential *** work explores the application of cellular materials with varied poisson’s ratios and provides guidance for the multi-functional design of sandwich cylindrical meta-structures.

关键词： Sandwich cylindrical shells poisson’s ratio pressure-resistant Buckling Vibroacoustic

Sea-level change in coastal areas of china:Status in 2021

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Advances in Climate Change research 2024年第3期15卷 515-524页

作者： Wen-Shan LI Hui WANG Wen-xi xiANG Ai-Mei WANG Wei-Qing XU Yu-xi JIANG xin-Hui WU Meng-Yuan QUAN National Marine Data and information Service Tianjin 300171China Ocean univ.rsity of Chin1 Qingdao 266100China univ.rsity of Michigan‒Shanghai Jiao Tong univ.rsity Joint institute Shanghai 200030China

The sea level in coastal areas of china reached the second highest in 2021,just after that recorded in *** force and dynamic analyses based on tide gauges,satellite observations,reanalysis data and regional numerical outputs were conducted to understand these abnormally high sea levels and determine their possible *** show that the coastal sea level of china had increased at an annual rate of 3.4±0.3 mm during 1980-2021,with an acceleration of 0.06±0.02 mm per *** superposition of significant oscillations of quasi-2,3-7,quasi-9,quasi-11,quasi-19 and 20-30 years contributed to the anomalously high sea *** negative-phased El Nino/Southern Oscillation was correlated with the anomalously high sea level and the north-south anti-phase pattern of the coastal sea level in ***,phase lags of 1-4 months occurred with the sea-level *** a decadal timescale,the pacific Decadal Oscillation(pDO)was negatively correlated with the anomalous mean sea level(MSL),and the negative-phased pDO contributed to the anomalous sea-level change in ***,the monthly MSL peaked in April and July,and the contribution of wind stress to the anomalously high sea level was 38.5%in the south of the Taiwan Strait in April and 30%along the coast of china in *** results were consistent with the tide gauge and satellite *** agreement was also observed between the coastal sea-level fingerprint and the air and sea surface temperatures.

关键词： Sealevel La Nina pDO Wind stress

Learning background restoration and local sparse dictionary for infrared small target detection

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Optoelectronics Letters 2024年第7期20卷 437-448页

作者： HE Yue ZHANG rui xi Chunmei ZHU Hu School of Communications and information Engineering Nanjing University of Posts and TelecommunicationsNanjing 210003China12

This paper proposes a method for learning background restoration for infrared small target detection,employing a local sparse dictionary alongside an equalized structural texture *** method is specifically designed for the detection of small infrared targets,accommodating various levels of brightness,spatial size,and *** proposed model intelligently combines global low-rankness and local sparsity to estimate the rank of the background tensor,leveraging spatial and structural information to overcome the limitations posed by insufficient detailed texture ***,a structural texture representation,combining local gradient maps and local intensity maps,is applied to emphasize small *** comparing our method with nine advanced and representative approaches and quantifying the comparison using various metrics,the experimental results indicate that our proposed method has achieved favorable outcomes in both quantitative assessments and visual results.

关键词： local structural overcome

An efficient schedulability analysis based on worst-case interference time for real-time systems

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Science china(information Sciences) 2024年第9期67卷 88-104页

作者： Hongbiao LIU Mengfei YANG Lei QIAO xi CHEN Jian GONG School of Computer Science and Technology Xidian University china Academy of Space Technology Beijing institute of Control Engineering

real-time systems are widely implemented in the Internet of Things(IoT) and safety-critical systems, both of which have generated enormous social value. Aiming at the classic schedulability analysis problem in real-time systems, we proposed an exact Boolean analysis based on interference(EBAI) for schedulability analysis in real-time systems. EBAI is based on worst-case interference time(WCIT), which considers both the release jitter and blocking time of the task. We improved the efficiency of the three existing tests and provided a comprehensive summary of related research results in the field. Abundant experiments were conducted to compare EBAI with other related results. Our evaluation showed that in certain cases, the runtime gain achieved using our analysis method may exceed 73% compared to the stateof-the-art schedulability test. Furthermore, the benefits obtained from our tests grew with the number of tasks, reaching a level suitable for practical application. EBAI is oriented to the five-tuple real-time task model with stronger expression ability and possesses a low runtime overhead. These characteristics make it applicable in various real-time systems such as spacecraft, autonomous vehicles, industrial robots, and traffic command systems.

关键词： five-tuple real-time task model real-time system spacecraft Internet of Things exact schedulability analysis worst-case interference time

Corporate Credit ratings Based on Hierarchical Heterogeneous Graph Neural Networks

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Machine Intelligence research 2024年第2期21卷 257-271页

作者： Bo-Jing Feng xi Cheng Hao-Nan Xu Wen-Fang Xue Center for research on intelligent perception and Computing National Laboratory of Pattern RecognitionInstitute of AutomationChinese Academy of SciencesBeijing 100190China

order to help investors understand the credit status of target corporations and reduce investment risks,the corporate credit rating model has become an important evaluation tool in the financial *** models are based on statistical learning,machine learning and deep learning especially graph neural networks(GNNs).However,we found that only few models take the hierarchy,heterogeneity or unlabeled data into account in the actual corporate credit rating ***,we propose a novel framework named hierarchical heterogeneous graph neural networks(HHGNN),which can fully model the hierarchy of corporate features and the heterogeneity of relationships between *** addition,we design an adversarial learning block to make full use of the rich unlabeled samples in the financial *** experiments conducted on the public-listed corporate rating dataset prove that HHGNN achieves SOTA compared to the baseline methods.

关键词： Corporate credit rating hierarchical relation heterogeneous graph neural networks adversarial learning

Microstructure,wear and friction behavior of CoCrAITaY-xCNTs composite coatings deposited by laser-induction hybrid cladding

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rare Metals 2024年第4期43卷 1815-1827页

作者： Sheng-Feng Zhou Yu Long Yan-Liang Yi Cheng Deng Lian-xi Hu institute of Advanced Wear&Corrosion resistant and Functional Materials Jinan UniversityGuangzhou510632China Wuhan National Laboratory for Optoelectronics(WNLO) Huazhong University of Science and TechnologyWuhan430074China MOE Key Laboratory of New processing Technology for Non-Ferrous Metals and Materials Guangxi Key Laboratory of Processing for Non-Ferrous Metals and Featured MaterialsGuangxi UniversityNanning530004China School of Mechatronics Engineering Guangdong Polytechnic Normal UniversityGuangzhou510635China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin150001China

To improve the wear performance of CoCrAlYTa coating,part of the carbon nanotubes(CNTs)chemically reacted with Ta to form reinforcement phase(TaC),while the other CNTs were retained as lubrication ***,the CoCrAlYTa-xCNTs(x=0,1,2,and 4;wt%)composite coatings were prepared by laserinduction hybrid cladding(LIHC),and the microstructure and wear resistance of coatings were systematically *** show that the coatings are mainly composed of TaC,y-(Co,Cr)andβ-(Co,Cr)*** the CNTs content increases from 0 wt%to 4 wt%,the volume fraction of TaC increases from 13.11 vol%to 16.12 vol%.Meanwhile,the nano-hardness ofγ-(Co,Cr)andβ-(Co,Cr)Al are improved from 7.49 and 9.72 to 9.36 and 11.19 Gpa,*** a result,the microhardness of coating increases from HV536.25 to HV 738.16,the wear rate decreases from32.4×10^(-3)to 6.1×10^(-3)mg·m^(-1),and the average friction coefficient decreases from 0.55 to *** good wear performance of the coating is attributed to the formation of TaC and the existence of remained CNTs lubricant film.

关键词： Carbon nanotube MCrAlY coating Friction and wear performance Laser-induction hybrid cladding

Method for signal decomposition and denoising based on nonuniform cosine-modulated filter banks

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progress in Natural Science:Materials International 2008年第10期18卷 1293-1298页

作者： Xuemei xie Li Li Guangming Shi Bin peng School of Electronic Engineering,xidian univ.rsity,xi’an,Box 134,Shaanxi 710071,china School of Electronic Engineering Xidian University Xi’an Box 134 Shaanxi 710071 China

In this paper,a novel method for signal decomposition and denoising is proposed based on a nonuniform filter bank (NUFB),which is derived from a uniform filter *** this method,the signal is firstly decomposed into M subbands using a uniform filter bank. Then according to their energy distribution,the corresponding consecutive filters are merged to compose the nonuniform *** the resulting NUFB,the signal can be readily matched and flexibly decomposed according to its power spectrum *** another advantage,this method can be used to detect and remove the narrow-band noise from the corrupted *** verify the proposed method,a simulation of extracting the main information of an audio signal and removing its glitch is given.

关键词： Signal decomposition Denoising Nonuniform filter bank Narrow-band noise

A unified Minorization-Maximization approach for estimation of general mixture models

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Applied Mathematics(A Journal of Chinese univ.rsities) 2024年第2期39卷 343-362页

作者： HUANG xi-fen LIU Deng-ge ZHOU Yun-peng ZHU Fei School of Mathematics Yunnan Normal UniversityKunming 650092China Department of Statistics and Actuarial Science The University of Hong KongHong KongChina

The mixed distribution model is often used to extract information from heteroge-neous data and perform modeling *** the density function of mixed distribution is complicated or the variable dimension is high,it usually brings challenges to the parameter es-timation of the mixed distribution *** application of MM algorithm can avoid complex expectation calculations,and can also solve the problem of high-dimensional optimization by decomposing the objective *** this paper,MM algorithm is applied to the parameter estimation problem of mixed distribution *** method of assembly and decomposition is used to construct the substitute function with separable parameters,which avoids the problems of complex expectation calculations and the inversion of high-dimensional matrices.

关键词： MM algorithm mixed distribution model parameter estimation assembly decomposition tech-nology parameter separation