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Optimization of spray conditions in cold spraying based on numerical analysis of particle velocity

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中国有色金属学会会刊：英文版 2004年第z1期14卷 43-48页

作者： li Wen-ya li Chang-jiu State Key Laboratory for Mechanical Behavior of Materials Xi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of MaterialsXi''an Jiaotong University Xi''an 710049 China

The effects of the parameters involved in cold spray on the acceleration of particles are systematically investigated by a CFD code in order to reveal the main factors influencing significantly particle velocity. The parameters involved include nozzle geometry parameters, processing parameters and properties of spray particles. It is found that driving gas type, operating pressure and temperature are main processing parameters which influence particle velocity. As for nozzle geometry, the expansion ratio and divergent section length of spray gun nozzle show significant effects. Moreover, the density, size and morphology of powder also have significant effects on particle velocity. The effects of those main parameters are summarized in a comprehensive equation obtained through nonlinear regression of the simulated results for the estimation of particle velocity. The interactions of the parameters on particle acceleration can be examined through the equation. Moreover, the optimization of the dimensions of spray gun nozzle and spray parameters can be realized based on the obtained results.

关键词： cold spraying numerical modeling particle acceleration impact velocity

图书馆老年用户数字技能提升的影响机理和对策路径研究

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大学图书情报学刊 2025年第1期43卷 91-100页

作者：李雅郑文昕苏州大学社会学院 215123 华东师范大学信息管理系上海200062

数字技术的迅猛发展对老年群体的数字技能提出了更高要求。公共图书馆具有提升老年群体数字技能水平的社会职责。文章通过对30位受访者的半结构化访谈,运用扎根理论,借助Nvivo12软件完成三级编码工作,揭示公共图书馆服务老年用户提升数... 详细信息

数字技术的迅猛发展对老年群体的数字技能提出了更高要求。公共图书馆具有提升老年群体数字技能水平的社会职责。文章通过对30位受访者的半结构化访谈,运用扎根理论,借助Nvivo12软件完成三级编码工作,揭示公共图书馆服务老年用户提升数字技能的影响机理,构建行为机制概念模型。分析结果显示,老年用户利用图书馆提升数字技能的意向受到行为态度、知觉行为控制、主观规范等因素的影响。文章就图书馆提供老年用户数字技能服务提出建议,以期为进一步完善图书馆服务提供参考。

关键词：数字技能公共图书馆行为模式老年群体扎根理论

Probing granular inhomogeneity of a particle-emitting source by imaging two-pion Bose–Einstein correlations

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Nuclear Science and Techniques 2021年第2期32卷 81-89页

作者： li-ya li Peng Ru Ying Hu School of Mathematics and Economics Hubei University of EducationWuhan 430205HubeiChina guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum MatterSouth China Normal UniversityGuangzhou 510006China

Using the source imaging technique in two-pion interferometry,we study the image of the hydrodynamic particle-emitting source with the HIJINg initial conditions for relativistic heavy-ion collisions on an event-by-event *** is shown that the initial-state fluctuations may give rise to bumpy structures of the medium during hydrodynamical evolution,which affects the two-pion emission space and leads to a visible two-tiered shape in the source function imaged using the two-pion Bose–Einstein *** two-tiered shape can be understood within a similar but more analytic granular source model and is found to be closely related to the introduced quantity n,which characterizes the granular inhomogeneity of the *** fitting the imaged source function with a granular source parametrization,we extract the granular inhomogeneity of the hydrodynamic source,which is found to be sensitive to both the gaussian smearing width of the HIJINg initial condition and the centrality of the collisions.

关键词： Heavy-ion collision Bose-Einstein correlations Imaging technique

行距配置和种植密度对棉花干物质生产及产量的影响

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作物学报 2025年第1期51卷 221-232页

作者：辛明华秘雅迪王国平李小飞李亚兵董合林韩迎春冯璐中国农业科学院棉花研究所/棉花生物学国家重点实验室河南安阳455000 中国农业科学院西部农业研究中心新疆昌吉831100

行距配置和种植密度是影响棉花产量和品质的重要因素。当前新疆棉花种植主要采用宽窄行配置,也有等行距配置方式,但对这两种方式的认识尚存在争议。为此,本研究以中棉所88号为供试材料,采用裂区设计,行距配置(等行距和宽窄行)为主区,种... 详细信息

行距配置和种植密度是影响棉花产量和品质的重要因素。当前新疆棉花种植主要采用宽窄行配置,也有等行距配置方式,但对这两种方式的认识尚存在争议。为此,本研究以中棉所88号为供试材料,采用裂区设计,行距配置(等行距和宽窄行)为主区,种植密度12×104株hm^(–2) (D1)、16×104株hm^(–2) (D2)和18×104株hm^(–2) (D3)为裂区,开展了2年大田试验,比较研究了行距配置和密度对棉花群体生长发育、干物质积累和分配、以及产量和纤维品质的影响。结果表明,中等密度(16×10^(4)株hm^(–2))下等行距和宽窄行处理组合的叶面积指数(LAI)增速、LAI峰值,以及吐絮期生殖器官生物量的分配比例均高于其他处理组合,且二者无显著差异。各处理组合间的棉花群体生长率(CgR)、净同化率(NAR)和棉铃生长率(BgR)均无显著差异。2年平均,中等密度下等行距和宽窄行处理组合的籽棉产量相当,纤维品质指标也无显著差异。表明在中等密度下,无论采用等行距还是宽窄行种植模式,均能达到理想的产量和品质。本研究为新疆棉花行距配置和密度选择提供了科学依据。

关键词：棉花单双行配置密度生长指标干物质积累与分配产量及品质

Study of the interactive effect of prey toxin and optimal foraging strategy on a predator-prey model

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International Journal of Biomathematics 2018年第4期11卷 95-110页

作者： ya li School of Mathematics and Systems Science & LMIB Beijing 100191 P. R. China

The optimal foraging theory predicts that predators choose prey with more net rate of energy intake and less energy costs if there are multiple food sources available. Toxins are found in many species in nature. Those toxins may be produced by prey as self- protection from predatory animals, or come from other sources such as pesticide residue. Therefore, it requires a balance between energy intake and toxicity damage. In order to study the interactive effect of prey toxin and optimal foraging strategy, we construct a predator-prey model with toxin-induced functional response and optimal foraging property. Dynamical analysis shows that the optimal strategy system presents more complex dynamical behavior than the fixed preference system. We conclude that optimal foraging strategy might play a key role in stabilizing or destabilizing the coexistence states of the species in the system, depending on the level of prey toxins.

关键词： Predator-prey model toxicity optimal foraging stability bifurcation.

Imaging and structural feature decomposition of a complex target using multi-aspect polarimetric scattering

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Science China(Information Sciences) 2016年第8期59卷 220-233页

作者： Yongchen li ya-Qiu JIN Key Laboratory for Information Science of Electromagnetic Waves Fudan University

Based on the Huynen parametric decomposition of target scattering matrix, the polarimetric ellipse parameters are transformed and applied to decomposition of scattering mechanisms of a complex target in VHR POL-SAR images(very high resolution, polarimetric synthetic aperture radar). Making use of multi-aspect(or circle-aspect) and wideband VHR POL-SAR images, scattering mechanisms of a volumetric target and its structural components are recognized over image pixels. Utilizing the layover features, the target height profile is also estimated from two-dimensional image. As example, polarimetric scattering data of some vehicles on ground, including multi-aspect simulated data and experimental measurements, are applied to validations of scattering mechanism decompositions and target structural feature recognition.

关键词： scattering mechanism polarimetric decomposition multi-aspect imaging target recognition

Target decomposition and recognition from wide-angle SAR imaging based on a gaussian amplitude-phase model

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Science China(Information Sciences) 2017年第6期60卷 212-224页

作者： Yongchen li ya-Qiu JIN Key Laboratory for Information Science of Electromagnetic Waves Fudan University

Wide-angle synthetic aperture radar(W-SAR) imaging accounts for multi-azimuthal scattering and is feasible for retrieving more comprehensive features of complex targets. Because a typical target is seen as composed of its components(typically, some simple geometric objects), a gaussian amplitude-phase(gAP)model has been developed for the analysis of multi-azimuthal scattering from these objects. Based on the timefrequency analysis of wide-angle scattering, the parameters of the gAP model were estimated, including the gaussian variance, the surface curvature, and the number of objects in all imaged pixels. Numerical simulations and real measurements demonstrate the capability of the gAP model for decomposing and recognizing complex electric-large targets.

关键词： wide-angle SAR gaussian amplitude-phase time-frequency target decomposition target recognition

Regional Multi-Agent Cooperative Reinforcement Learning for City-Level Traffic grid Signal Control

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IEEE/CAA Journal of Automatica Sinica 2024年第9期11卷 1987-1998页

作者： Yisha li ya Zhang Xinde li Changyin Sun School of Automation Southeast UniversityNanjing 210096 Key Laboratory of Measurement and Control of Complex Systems of Engineering Ministry of EducationSoutheast UniversityNanjing 210096China

This article studies the effective traffic signal control problem of multiple intersections in a city-level traffic system.A novel regional multi-agent cooperative reinforcement learning algorithm called RegionSTlight is proposed to improve the traffic *** a regional multi-agent Q-learning framework is proposed,which can equivalently decompose the global Q value of the traffic system into the local values of several regions Based on the framework and the idea of human-machine cooperation,a dynamic zoning method is designed to divide the traffic network into several strong-coupled regions according to realtime traffic flow *** order to achieve better cooperation inside each region,a lightweight spatio-temporal fusion feature extraction network is *** experiments in synthetic real-world and city-level scenarios show that the proposed RegionS Tlight converges more quickly,is more stable,and obtains better asymptotic performance compared to state-of-theart models.

关键词： Human-machine cooperation mixed domain attention mechanism multi-agent reinforcement learning spatio-temporal feature traffic signal control

Microstructure evolution and precipitation behavior of Al-Mg-Si alloy during initial aging

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China Foundry 2023年第1期20卷 57-62页

作者： ya-ya Zheng Bing-hui Luo Wei Xie Wang li Department of Materials Engineering Hunan University of HumanitiesScience and TechnologyLoudi 417000HunanChina College of Materials Science and Engineering Central South UniversityChangsha 410083China Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle Changsha University of Science&TechnologyChangsha 410114China

The microstructure evolution and precipitation behavior of Al-Mg-Si alloy during initial aging were studied using hardness testing, conductivity testing, differential scanning calorimetry(DSC), and high resolution transmission electron microscopy(HRTEM). The results show that the precipitation sequence of the Al-Mg-Si alloy during initial aging can be represented as: supersaturated solid solution → spherical Mg/Si clusters → needle-like guinier Preston(gP) zone → β″. Clusters are completely coherent with the Al matrix. The gP zone with relatively complete independent lattice parameters that differ slightly from the Al matrix parameters, is oriented along the direction of Aland lying on {111}Alplane. The strength of the Al-Mg-Si alloy is greatly enhanced by the threedimensional strain field that exists between the β″ phase and the two {200}Alplanes. After aging at 170 ℃ for 6 h, the hardness reaches the peak of 127 HV and remains for a long time. At this stage, the electrical conductivity keeps relatively stable due to the formation of coherent precipitates(Mg/Si clusters/gP zones) and the reduction in solute atom concentration in the Al matrix. The severe coarsening and decreased number density of the β″ phase during the over-aging stage result in a significant decrease in the hardness.

关键词： Al-Mg-Si alloy precipitation behavior strengthening mechanism strain field β″