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Friction and wear properties of casting in-situ silicon particle reinforced za27 composites

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China Foundry 2009年第1期6卷 1-8页

作者： Chen Tijun Yuan Chengren Fu Mingfeng ma Ying LiYuandong Hao Yuan Key Laboratory of Gansu Advanced Nonferrous materials Lanzhou University of Technology Lanzhou 730050 China

The effects of silicon particle content and testing temperature on friction and wear properties of casting in-situ silicon particle reinforced za27 composites were *** wear mechanisms were mainly discussed by observations of both worn surfaces and their side *** results indicated that the variations of wear resistance with increasing of silicon particle content,at all of the testing temperatures applied,showed a similar tendency with a manner of non-monotonous *** was surprised that the wear resistance decreased with the increase of silicon particle content from 2 vol.%to 5 vol.%,while it increased when the content was less than 2 vol.%or more than 5 vol.%.Similarly,the friction coefficient also did not change *** dominative wear mechanism changed from a relatively severe regime of plastic deformation accompanied by adhesion wear to a mild regime of smear,then to a very severe regime of severe plastic deformation induced wear,and finally again to a relatively mild regime of smear accompanied by abrasive wear as the silicon content *** wear resistance always decreased with elevating testing temperature,but the decrease ranges were different for the composites with different silicon *** friction coefficients changed irregularly for the different composites with the increase of testing ***,the wear mechanism alternated from a mild regime of smear accompanied by abrasive wear to a severe regime of plastic deformation accompanied by adhesion wear.

关键词：合金硅粒子铸造技术摩擦磨损性能耐磨性

Small-animal PET demonstrates brain metabolic change after using bevacizumab in a rat model of cerebral ischemic injury

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Neuroscience Bulletin 2014年第5期30卷 838-844页

作者： Ying Dong Fahuan Song Jianjuan ma Xuexin He Said Amer Weizhong Gu Mei Tian Department of Oncology Department of Nuclear Medicine The Second Affiliated Hospital of Zhejiang University School of Medicine Zhejiang University Medical PET Center Institute of Nuclear Medicine and Molecular Imaging of Zhejiang University Key Laboratory of Medical Molecular Imaging of Zhejiang Province Department of Zoology Faculty of ScienceKafr El Sheikh University Department of Pathology The Children's Hospital of Zhejiang University School of Medicine

ABSTRACT To evaluate the effect of bevacizumab on cerebral ischemia, we used 2-deoxy-2-18F-fluoro-D-glucose （18F-FDG） small-animal positron emission tomography （PET） in the middle cerebral artery occlusion （MCAO） rat model. After baseline neurologic function tests and PET studies, MCAO Sprague-Dawley rats received bevacizumab or normal saline （controls）. Weekly PET imaging and neurologic function tests showed that the 18F-FDG accumulation in the bevacizumab group was similar to that in the controls during the first 2 weeks, but lower than in controls at weeks 3 and 4. However, no difference was found in neurological scores between the groups. The number of von Willebrand factor-positive cells in the bevacizumab group was lower than that in controls. The expression of vascular endothelial growth factor was higher than in controls at week 4. These results suggested that bevacizumab does not influence functional recovery in this model of cerebral ischemia during a 4-week period, but inhibits vascular formation and metabolic recovery, which may be considered in cancer patients with a recent ischemic stroke.

关键词： cerebral ischemia bevacizumab positron emission tomography cancer

MICROSTRUCTURE ANALYSIS AND MECHANICAL PROPERTIES OF Zn-Al ALLOY ROD PRODUCED BY HEATED MOLD CONTINUOUS CASTING

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Acta Metallurgica Sinica(English Letters) 2003年第3期16卷 241-248页

作者： Y.ma Y.Hao F.Y.Yan H.J.Liu State Key Laboratory of Advanced Nonferrous materials Lanzhou University of Science & Technology Lanzhou 730050 ChinaState Key Laboratory of Advanced Nonferrous Materials Lanzhou University of Science & Technology Lanzhou 730050 ChinaState Key Laboratory of Advanced Nonferrous Materials Lanzhou University of Science & Technology Lanzhou 730050 ChinaSchool of Mechano-Electronic EngineeringHua Qian University Quanzhou 362011China

The new technology of continuous casting by heated mold was used to produce directional solidification za.a.loy lines to eliminate the inter defects of these lines and increase their mechanical properties. The results are as follows: (1) The microstruc-ture of the za.a.loy lines is the parallel directional dendritic columnar crystal. Every dendritic crystal of eutectic alloy za5 was composed of many layer eutectic β and η phases. The micro structure of hypereutectic za.a.loys is primary dendritic crystal and interdendritic eutectic structure. The primary phase of za8 and za12 is β, among them, but the primary phase of za22 and za27 is a. (2) Through the test to the as-cast za.a.loy lines made in continuous casting by heated mold, it is found that the tensile strength and hardness increase greatly, but the elongation decreases. With the increase of aluminum amount from za 5 to za 12, za22 and za27, the tensile strength increases gradually. za27 has the best comprehensive mechanical properties in these four kinds of za.a.loys. (3) Heat treatment can decrease the dendritic segregation and improve the elongation of za.a.loy, but make their strength decrease slightly.

关键词： zinc-aluminum alloy heated mold continuous casting mechanical properties heat treatment

高技术产业集聚促进绿色发展效率了吗?--动态与空间溢出视角

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管理现代化 2022年第3期42卷 24-31页

作者：马亮高峻兰州理工大学经济管理学院甘肃兰州730000

基于动态面板模型与空间计量模型,探究了中国省际高技术产业集聚及其集聚模式对绿色发展效率的影响。研究结果表明:高技术产业集聚和绿色发展效率在地理分布上均呈现东高西低的空间分布特征;基于动态视角,高技术产业集聚有助于绿色发展... 详细信息

基于动态面板模型与空间计量模型,探究了中国省际高技术产业集聚及其集聚模式对绿色发展效率的影响。研究结果表明:高技术产业集聚和绿色发展效率在地理分布上均呈现东高西低的空间分布特征;基于动态视角,高技术产业集聚有助于绿色发展效率的提升且两者之间存在“U”型曲线关系,专业化集聚促进区域绿色发展,而多样化集聚抑制区域绿色发展;基于空间溢出视角,专业化集聚对邻近地区存在显著负向溢出效应,而多样化集聚对邻近地区存在显著正向溢出效应;从发展阶段角度看,研究期间高技术产业集聚始终对绿色发展效率产生促进作用,但呈下降趋势,专业化集聚对绿色发展效率均表现出促进效果,而多样化集聚对绿色发展效率表现出由负到正的影响特征。

关键词：高技术产业集聚绿色发展效率专业化集聚多样化集聚

Multi-scale UDCT dictionary learning based highly undersampled MR image reconstruction using patch-based constraint splitting augmented Lagrangian shrinkage algorithm

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Frontiers of Information Technology & Electronic Engineering 2015年第12期16卷 1069-1087页

作者： Min YUAN Bing-xin YANG Yi-de ma Jiu-wen ZHANG Fu-xiang LU Tong-feng ZHANG School of Information Science & Engineering Lanzhou University

Recently, dictionary learning(DL) based methods have been introduced to compressed sensing magnetic resonance imaging(CS-MRI), which outperforms pre-defined analytic sparse priors. However, single-scale trained dictionary directly from image patches is incapable of representing image features from multi-scale, multi-directional perspective, which influences the reconstruction performance. In this paper, incorporating the superior multi-scale properties of uniform discrete curvelet transform(UDCT) with the data matching adaptability of trained dictionaries, we propose a flexible sparsity framework to allow sparser representation and prominent hierarchical essential features capture for magnetic resonance(MR) images. Multi-scale decomposition is implemented by using UDCT due to its prominent properties of lower redundancy ratio, hierarchical data structure, and ease of implementation. Each sub-dictionary of different sub-bands is trained independently to form the multi-scale dictionaries. Corresponding to this brand-new sparsity model, we modify the constraint splitting augmented Lagrangian shrinkage algorithm(C-SALSA) as patch-based C-SALSA(PB C-SALSA) to solve the constraint optimization problem of regularized image reconstruction. Experimental results demonstrate that the trained sub-dictionaries at different scales, enforcing sparsity at multiple scales, can then be efficiently used for MRI reconstruction to obtain satisfactory results with further reduced undersampling rate. Multi-scale UDCT dictionaries potentially outperform both single-scale trained dictionaries and multi-scale analytic transforms. Our proposed sparsity model achieves sparser representation for reconstructed data, which results in fast convergence of reconstruction exploiting PB C-SALSA. Simulation results demonstrate that the proposed method outperforms conventional CS-MRI methods in maintaining intrinsic properties, eliminating aliasing, reducing unexpected artifacts, and removing noise. It

关键词： Compressed sensing(CS) magnetic resonance imaging(MRI) Uniform discrete curvelet transform(UDCT) Multi-scale dictionary learning(MSDL) Patch-based constraint splitting augmented Lagrangian shrinkage algorithm(PB C-SALSA)

Synthesis and application of chiral N,N'-dialkylated cyclohexanediamine for asymmetric hydrogenation of aryl ketones

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Chinese Chemical Letters 2011年第2期22卷 155-158页

作者： Meng Lin ma Chuan Hong Ren Ya Jing Lv Hua Chen Xian Jun Li Department of Chemistry Xihua UniversityChengdu 610039China Key Lab of Green Chemistry and Technology Ministry of EducationThe Institute of Homogeneous Catalysis Faculty of ChemistrySichuan UniversityChengdu 610064China

Chiral N,N＇-dialkylated cyclohexanediamine derived ligands have been synthesized and used in the asymmetric hydrogenation of aryl *** active alcohols with up to 90%enantiomeric excess were obtained in high yields.

关键词： Chiral diamine Aryl ketone Asymmetric hydrogenation Ruthenium complex

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果园核桃机械化采收装置的设计

中国农机化学报 2013年第5期34卷 185-189页

作者：高团结坎杂马俊贵谢凡何荣石河子大学机械电气工程学院新疆石河子832003

为解决我国人工采收核桃费时费力、效率低等问题，设计了一种曲柄连杆振动式果园核桃机械采收装置。本文阐述了该装置结构及工作原理，主要对装置的夹持振动机构、传动系统和集果装置进行了设计。该采收装置利用曲柄连杆机构运动原理，... 详细信息

为解决我国人工采收核桃费时费力、效率低等问题，设计了一种曲柄连杆振动式果园核桃机械采收装置。本文阐述了该装置结构及工作原理，主要对装置的夹持振动机构、传动系统和集果装置进行了设计。该采收装置利用曲柄连杆机构运动原理，以高振动频率低振幅的往复直线运动方式实现了果园核桃的机械化采收。本文设计的采收装置预期达到生产率≥20株／h；采净率≥80％，初步确定该采收装置的振动频率为500～700次／min，振幅为30-40mm。

关键词：果园核桃采收装置曲柄连杆机械化

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轴辐式应急救援网络规划

交通运输工程学报 2023年第3期23卷 198-208页

作者：马昌喜石褚巍杜波兰州交通大学交通运输学院甘肃兰州730070 兰州交通大学高原铁路运输智慧管控铁路行业重点实验室甘肃兰州730070 兰州财经大学信息工程学院甘肃兰州730020 伍伦贡大学智能基础设施研究中心新南威尔士伍伦贡2522

为了实现对受灾城市的快速支援,同时尽可能降低应急救援网络的建设成本,以应急救援站选址和应急救援通道布局为落脚点,研究了三级轴辐式应急救援网络的多目标规划方法;考虑轴辐式网络的多级结构及应急救援站间的连通关系特征,以三级应... 详细信息

为了实现对受灾城市的快速支援,同时尽可能降低应急救援网络的建设成本,以应急救援站选址和应急救援通道布局为落脚点,研究了三级轴辐式应急救援网络的多目标规划方法;考虑轴辐式网络的多级结构及应急救援站间的连通关系特征,以三级应急救援站选址、应急救援站间的连通关系及应急救援通道等级为决策变量,以各级应急救援站的建设成本和网络平均救援时间最小为双目标函数,构建三级轴辐式应急救援网络规划模型;结合决策变量的特征为三级轴辐式应急救援网络规划模型设计了三段式编码结构的小生境Pareto遗传算法;依托甘肃省14个城市的公路网络进行应急救援网络的建模求解,验证方法的有效性,并将优化结果与传统三级应急救援网络进行了对比。研究结果表明:三段式编码结构的小生境Pareto遗传算法能够有效求解该轴辐式应急救援网络规划模型;与传统应急救援网络模型的最优解相比,选取的Pareto解方案可使三级轴辐式应急救援网络在应急救援站的建设成本上降低8.3%,在网络平均救援时间上加快了3.5 h,其优化结果可支配传统应急救援网络的最优解。可见,提出的三级轴辐式应急救援网络规划方法能够兼顾轴辐式网络的集约特性,同时取得更短的应急救援时间。

关键词：交通规划轴辐式应急救援网络多目标规划应急救援站应急救援通道平均救援时间小生境Pareto遗传算法

卡姆斯特煤田侏罗系八道湾组地层层序及聚煤特征

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中国地质 2011年第5期38卷 1312-1323页

作者：吴天伟田继军木合塔尔.扎日陈斌马帅柳磊新疆大学地质与勘查工程学院新疆乌鲁木齐830047

综合利用卡姆斯特煤田钻孔测井、野外露头及古生物化石等资料,应用经典层序地层学基本理论和方法,对卡姆斯特煤田八道湾组进行了层序地层划分,共识别出SQ1和SQ2两个三级层序,并根据地层叠置样式、沉积旋回特征细分为6个体系域。通过沉... 详细信息

综合利用卡姆斯特煤田钻孔测井、野外露头及古生物化石等资料,应用经典层序地层学基本理论和方法,对卡姆斯特煤田八道湾组进行了层序地层划分,共识别出SQ1和SQ2两个三级层序,并根据地层叠置样式、沉积旋回特征细分为6个体系域。通过沉积基础图件、沉积环境的分析明确了研究区八道湾组沉积演化主要受古地形起伏、古气候条件等古地理因素的综合影响。确定研究区内目的层段主要在高位和低位时期聚煤,湖侵时期不利于聚煤。通过详细研究卡姆斯特煤田八道湾组的沉积环境和聚煤特征,为今后寻找和开发卡姆斯特地区煤炭资源提供地质依据。

关键词：卡姆斯特煤田八道湾组层序地层聚煤特征侏罗系准噶尔盆地