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基于非均质模型的水稳碎石材料细观开裂行为

吉林大学学报（工学版） 2024年第5期54卷 1258-1266页

作者：赵晓康胡哲牛振兴张久鹏裴建中温永长安大学公路学院西安710064

本文采用离散元法(DEM)研究非均质水稳碎石(CSM)材料的细观开裂行为,基于Weibull材料随机场,建立了不同均质度水平的CSM细观断裂模型,通过虚拟半圆弯曲(SCB)试验模拟细观开裂过程,分析砂浆基体均质度的影响。结果表明:CSM裂纹沿着砂浆... 详细信息

本文采用离散元法(DEM)研究非均质水稳碎石(CSM)材料的细观开裂行为,基于Weibull材料随机场,建立了不同均质度水平的CSM细观断裂模型,通过虚拟半圆弯曲(SCB)试验模拟细观开裂过程,分析砂浆基体均质度的影响。结果表明:CSM裂纹沿着砂浆薄弱点和界面共同扩展,砂浆基体的断裂占主导地位。峰值强度和破坏形变随均质度的提高而增大,砂浆中少量的性能薄弱点有益于改善结构形变特性而提升其整体强度,适当均质度水平有助于CSM材料抗裂性能的发挥。

关键词：道路工程水泥稳定碎石细观非均质半圆弯曲试验离散元法

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围绕创新链布局产业链:基于中关村科技园周边新企业进入的分析

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中国工业经济 2024年第1期 75-92页

作者：陈强远殷赏程芸倩孙久文中国人民大学国家发展与战略研究院中国人民大学应用经济学院

围绕创新链布局产业链是培育未来产业的主要思路,而产业链与创新链的空间融合是未来产业布局的突出特征。就产业布局为何邻近创新集群,鲜有研究给出充分的学理依据和经验证据。基于中国工商企业登记注册数据、中国企业专利授权和转移数... 详细信息

围绕创新链布局产业链是培育未来产业的主要思路,而产业链与创新链的空间融合是未来产业布局的突出特征。就产业布局为何邻近创新集群,鲜有研究给出充分的学理依据和经验证据。基于中国工商企业登记注册数据、中国企业专利授权和转移数据、中国税收调查数据、百度地图兴趣点(POI)数据等形成的匹配数据,本文利用中关村科技园各分园成立时点构建空间双重差分模型,首次考察了创新集群对城市内新企业空间布局的影响和作用机制。研究发现:创新集群对新创企业表现为明显的向心力,将吸引新创企业更多入驻距离创新集群0—1.4千米的地理范围内,并且这一结果在科技分园主导产业的下游产业体现得更明显;企业空间布局邻近创新集群,有利于新创企业的技术获取、声誉溢价和信息捕获;新创企业邻近创新集群布局,将显著提高企业的经营绩效和生存概率。本文研究既为学理上认识创新集群对一般性企业选址的影响提供重要启示,也为实践中推动产业链创新链深度融合提供现实依据。

关键词：创新集群产业链空间布局新企业进入空间溢出中关村科技园

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

Microstructure evolution of cold-sprayed coating during deposition and through post-spraying heat treatment

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中国有色金属学会会刊：英文版 2004年第Z1期14卷 49-54页

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

The microstructural features of cold-sprayed coatings were investigated using Cu, Ti and Zn feedstocks by optical microscopy, scanning electron microscopy and transmission electron microscopy to reveal the microstructure evolution mechanisms in cold spray. Four typical effects including tamping, refinement, impact-induced fusion and annealing were examined on microstrueture. It is found that the microstructure of cold spray coating is remarkably influenced by spray materials. Ti coatings consist of evident porous layer and Cu coatings present a limited porous layer only near the surface. It is clear that the successive tamping effect and dynamic refinement of grains significantly influence the microstructure evolution of cold-sprayed coating. The tamping effect leads to the densification of porous coating layer gradually and the refinement effect leads to the formation of fine microstructure. It is considered that the large difference in the formation of porous layer is attributed to the dynamic impact pressure and hardenability of materials. It is also found that the impact-induced fusion during deposition of Zn coating can also modify the interfacial microstructure between particles in cold spray coating. Moreover, the nanocrystalline phase can be formed at the interfaces among particles resulting from the localized melting of the interfaces and tamping effect. Furthermore, the annealing treatment can modify the microstructure and property of a cold-sprayed coating.

关键词： cold spraying coating microstructure evolution annealing treatment

Effect of Rare Earth on Void band of Diffusion Layer and Properties of Aluminized Steel

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Journal of Iron and Steel Research International 2006年第5期13卷 60-64,78页

作者： ZHANG Wei FAN Zhi-kang HU Peng-fei LONG Yong-qiang LIU Hua wen jiu-ba School of Materials Science and Engineering Xi＇an University of Technology Xi＇an 710048 Shaanxi China Department of Materials Engineering Luoyang College of Technology Luoyang 471003 Henan China School of Materials Science and Engineering Henan University of Science and Technology Luoyang 471003 Henan China

The effects of the addition of rare earth （RE） elements on the void band in the diffusion layer, and the re sistances to both oxidation and spalling of aluminized steel were investigated through high temperature oxidation and spalling tests. The results showed that RE had significant effects on the void band in the diffusion layer and the properties of aluminized steel. After diffusion treatment, a considerable number of the voids between the middle layer and transitional layer of pure aluminized coating, aggregated into wavy-line-shaped void bands parallel to the outer surface. For the RE added aluminized coating, only a few voids aggregated into intermittent block shapes. During high temperature oxidation at 800 ℃ for 200 h, the wavy void band of pure aluminized coating aggregated further into a linear crack parallel to the outer surface, and the internal oxidation occurred within them; the open cracks perpendicular to the surface penetrated through the diffusion layer. For the RE added aluminized coating, only a few voids aggregated into intermittent meniscus shapes. During cyclic spalling tests, the peeling, spallation, and pulver ulent cracking occurred along the void band in the diffusion layer of pure aluminized coating, but only a little spallation occurred in the diffusion layer of the RE-added aluminized coating, in which cracks perpendicular to the surface were much smaller than those of pure aluminized coating and did not penetrate through the diffusion layer. It is evident that RE addition can restrain the formation and aggregation of voids and subsequently improve the resistances to oxidation and spalling. The mechanism of the RE effect on the void band in the diffusion layer is also discussed.

关键词： rare earth void band crack internal oxidation oxidation resistance spalling resistance aluminized steel

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新型热泵增湿除湿海水淡化系统性能研究

现代化工 2024年第9期44卷 227-231页

作者：王炳东沈九兵朱文婷王文欢江苏科技大学能源与动力学院江苏镇江212103

为解决增湿除湿海水淡化技术高能耗问题,提出了一种新型热泵增湿除湿海水淡化系统,将热泵蒸发器用作二级除湿器,并增设过冷器对深度除湿后的空气进行复温。选用R134a为热泵工质,通过数学模型的建立与求解,分析讨论了制冷剂充注量、进料... 详细信息

为解决增湿除湿海水淡化技术高能耗问题,提出了一种新型热泵增湿除湿海水淡化系统,将热泵蒸发器用作二级除湿器,并增设过冷器对深度除湿后的空气进行复温。选用R134a为热泵工质,通过数学模型的建立与求解,分析讨论了制冷剂充注量、进料海水温度和液气质量比对系统性能的影响,并与现有文献中的热泵增湿除湿海水淡化系统性能进行对比。结果表明,系统存在最佳的制冷剂充注量、进料海水温度和液气质量比;当进料海水流量为720 kg/h时,最佳制冷剂充注量为240 kg/h,对应的最佳淡水产量和造水比分别为28.83 kg/h和7.21,均优于文献报道值,表明新系统具备实际产品开发的价值和广阔的应用前景。

关键词：增湿除湿热泵海水淡化淡水产量造水比

基于SBE-SD法的清式家具雕刻图案美感度影响因素探究

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林产工业 2024年第4期61卷 49-54页

作者：朱龄高婧淑傅雷把小宁吕九芳南京林业大学家居与工业设计学院江苏南京210037 南京林业大学艺术设计学院江苏南京210037

为探究清式家具雕刻图案的审美要素和规律,本文在问卷调查的基础上,利用SBE法和SD法对清式家具雕刻图案进行美感度评价及对其影响因素进行分析。结果表明:构图主次和布局协调感直接影响清式家具雕刻图案的美感度评价值,而动态关系、尺... 详细信息

为探究清式家具雕刻图案的审美要素和规律,本文在问卷调查的基础上,利用SBE法和SD法对清式家具雕刻图案进行美感度评价及对其影响因素进行分析。结果表明:构图主次和布局协调感直接影响清式家具雕刻图案的美感度评价值,而动态关系、尺度比例和元素丰富度则为间接影响,且元素丰富度的影响程度略高于尺度比例。线性回归方程构建的数学模型分别为Y_(SBE)=0.555A_(3)(构图主次)+0.419A_(5)(布局协调感)和Y_(SBE)=0.27A_(6)(动态关系)+0.239A_(1)(尺度比例)=0.27A_(6)(动态关系)+0.218A_(4)(元素丰富度)。研究结果对于探究清式家具雕刻图案的美学规律具有积极的探索意义。

关键词：清式家具雕刻图案 SBE法 SD法美感度

Structural and mechanical properties of 7075 alloy strips fabricated by roll-casting in a static magnetic field

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International Journal of Minerals,Metallurgy and Materials 2014年第7期21卷 696-701页

作者： Xin Su Guang-ming Xu jiu-wen Jiang Key Laboratory of Ministry of Education for Electromagnetic Processing of Materials Northeastern University Foshan Scien Aluminum Co. Ltd.

The influences of a 0.2 T static magnetic field on the microstructure of 7075 aluminum alloys sheets produced with a twin-roll continuous caster at 675℃ were investigated in this paper. Under a uniform magnetic field, the primary dendrites were refined and tended to be equiaxed. The microstructure consisted of an intermediate case between dendritic and equiaxed grains. Moreover, the use of an external static field in the twin-roll casting process can reduce heat discharge, resulting in a decrease in undercooling, and may also account for the abatement of segregation bands. In addition, the static magnetic field effectively improved the solute mixing capacity, and the added atoms more easily diffused from precipitates to theα-Al matrix, which resulted in an increase in the mechanical properties of the rolled sheets. Specimens prepared both in the presence of a static magnetic field and in the absence of a static magnetic field exhibited brittle-fracture characteristics.

关键词： aluminum alloys magnetic field roll-casting mechanical properties

Dual-function terahertz metasurface based on vanadium dioxide and graphene

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Chinese Physics B 2022年第9期31卷 286-292页

作者： jiu-Sheng Li Zhe-wen Li Centre for THz Research China Jiliang UniversityHangzhou 310018China

A dual-function terahertz metasurface based on VO_(2) and graphene is proposed in this *** consists of a gold layer embedded with VO_(2) patches,a SiO_(2) spacer layer,a VO_(2) layer,graphene and a SiO_(2) spacer *** the bottom VO2 layer is in the metallic state,the designed metasurface can achieve *** the top VO_(2) patches are in the metallic state,the proposed metasurface can be used as a single-band absorber with terahertz absorptance of 99.7% at 0.736 *** the top VO2 patches are in the insulating state,the designed structure behaves as a dual-band absorber with an absorptance of 98.9%at 0.894 THz and 99.9% at 1.408 *** addition,the absorber is polarization insensitive and keeps good performance at large angles of *** the bottom VO_(2) is in an insulating state,the metasurface shows electromagnetically induced *** transparent window can be dynamically regulated by controlling the chemical potential of *** proposed metasurface exhibits the advantages of terahertz absorption,electromagnetically induced transparency and dynamic control,which provides more options for the design of terahertz devices in the future.

关键词： metasurface switchable terahertz absorber electromagnetically induced transparency