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Laser Polishing of Laser Powder Bed Fusion AlSi10Mg Parts—Influence of Initial Surface Roughness on Achievable Surface Quality 认领
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作者 Markus Hofele Andre Roth +3 位作者 Jochen Schanz David K. Harrison Anjali K. M. De Silva Harald Riegel 《材料科学与应用期刊(英文)》 2021年第1期15-41,共27页
Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing technique, which allows production of highly complex solid metal parts with good mechanical properties, compared to conventionally manufactured parts. Nevert... Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing technique, which allows production of highly complex solid metal parts with good mechanical properties, compared to conventionally manufactured parts. Nevertheless, the layer-by-layer fabrication process also offers several disadvantages, including a relatively high surface roughness depending on the shape of the component, its position and orientation during the fabrication process. This paper deals with investigations on the surface roughness reduction capability, and residual surface structures by laser polishing of LPBF AlSi10Mg parts under varying initial surface roughness in order to investigate the influence of the surface behavior and initial surface roughness to the achievable surface quality by laser polishing. Hereto test specimens with varying fabrication orientations regarding to the built platform are printed and further polished. Thereby the initial arithmetic roughness varies between 19.2 μm and 8.0 μm. It could be shown that the achievable surface roughness by laser polishing with continuous and pulsed laser radiation is increasing with rising initial roughness, but the relative roughness reduction is almost constant in the range of 95% - 97.5%. The analyzation of the residual roughness structures shows, that the main roughness differences is found in the middle and long structure wavelength regime, which are directly depending on the initial surface structures of 3D printing. 展开更多
关键词 Additive Manufacturing Surface Roughness Aluminium AlSi10Mg Laser Polishing Fabrication Orientation
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中国城市社区协商民主实践创新:定位、特征与时代意义 认领
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作者 李欣 《陕西行政学院学报》 2021年第1期65-69,共5页
21世纪以来,随着"中国特色社会主义协商民主"概念的提出,协商民主作为一种民主形式和制度安排,已经成为当代中国特色社会主义民主政治的重要内容。在政府改革的逻辑中,城市社区协商民主是作为中国协商民主体系的多层次形态之... 21世纪以来,随着"中国特色社会主义协商民主"概念的提出,协商民主作为一种民主形式和制度安排,已经成为当代中国特色社会主义民主政治的重要内容。在政府改革的逻辑中,城市社区协商民主是作为中国协商民主体系的多层次形态之一而被纳入改革视域的。伴随着国家对基层认识和管理方式的不断深化,推进城市社区协商民主已经成为中国民主政治制度中不可或缺的组成部分。因此,深化对我国城市社区协商民主的定位、主要特征与时代意义等重要问题的认识,将有助于推进基层社区协商民主实践的进一步发展,完善中国特色社会主义协商民主体系。 展开更多
关键词 协商民主 城市社区 定位 特征
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碳纳米纤维增强聚甲醛复合材料制备及性能 认领
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作者 孟晓宇 吕毅男 +3 位作者 叶海木 丛川波 周琼 徐立新 《工程塑料应用》 CAS 北大核心 2021年第1期7-12,19,共7页
通过纳米碳纤维(CNFs)在聚甲醛(POM)基体中的均匀分散以及取向,制备了具有优异力学性能和热性能的POM/CNFs复合材料。利用扫描电子显微镜、透射电子显微镜、拉伸性能测试、热重分析、动态热机械分析测试表征了POM/CNFs复合材料的结构和... 通过纳米碳纤维(CNFs)在聚甲醛(POM)基体中的均匀分散以及取向,制备了具有优异力学性能和热性能的POM/CNFs复合材料。利用扫描电子显微镜、透射电子显微镜、拉伸性能测试、热重分析、动态热机械分析测试表征了POM/CNFs复合材料的结构和力学、热学性能。结果表明,CNFs与POM分子链形成氢键相互作用,促进了CNFs在POM基体内分散,同时使POM/CNFs复合材料的结晶度显著提高。随着CNFs含量增加,POM/CNFs复合材料的拉伸强度、储能模量和损耗模量均得到提高。当添加0.5%的CNFs时,拉伸强度、储能模量及损耗模量分别提高了20.5%,127%和58%。进一步研究了高温拉伸对POM/CNFs复合材料性能的影响。结果表明,CNFs沿拉伸方向定向排列,同时复合材料拉伸后结晶度提高,拉伸强度显著增加。 展开更多
关键词 聚甲醛 纳米碳纤维 取向 力学性能 结晶
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子宫穴考 认领
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作者 付思思 岳增辉 《河南中医》 2021年第3期346-348,共3页
《备急千金要方·卷三·妇人方中》最早对子宫穴的位置进行了描述,位于"侠玉泉三寸"。由于对"侠"字释义理解的错误,导致《针灸大成》认为,本穴位于"中极两旁各开三寸",从而错误定位子宫穴的位置... 《备急千金要方·卷三·妇人方中》最早对子宫穴的位置进行了描述,位于"侠玉泉三寸"。由于对"侠"字释义理解的错误,导致《针灸大成》认为,本穴位于"中极两旁各开三寸",从而错误定位子宫穴的位置,引起诸多争议。应将中极穴旁开1.5寸和旁开3寸均归为子宫穴,临床运用时,在此4个点周围寻找疾病反应点或敏化点(如热敏点、痛敏点),最终确定穴位位置。如果未发现疾病反应点或敏化点,则四点同取,加强疗效。 展开更多
关键词 子宫穴 定位 考证
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Orientations of nuclei during static recrystallization in a cold-rolled Mg-Zn-Gd alloy 认领
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作者 L.Y.Zhao H.Yan +1 位作者 R.S.Chen En-Hou Han 《材料科学技术:英文版》 SCIE EI CAS 2021年第1期162-167,共6页
The static recrystallization process of a cold-rolled Mg-Zn-Gd alloy was tracked by a quasi-in-situ electron backscatter diffraction method to investigate the orientations of nuclei.The results show that orientation d... The static recrystallization process of a cold-rolled Mg-Zn-Gd alloy was tracked by a quasi-in-situ electron backscatter diffraction method to investigate the orientations of nuclei.The results show that orientation distribution of nuclei is associated with nucleation mechanism.The continuous static recrystallization nuclei display similar orientations to the parent grains with TD orientation.Differently,discontinuous static recrystallization nuclei formed within the parent grains(TD-45~0 orientation) show random orientations and a variety of misorientation angles but preferred axes <5273> or <5270>.Interestingly,a special oriented nucleation is found.Discontinuous static recrystallization nuclei originated from boundaries of the parent grain(TD-70° orientation) show concentrated TD orientations in another side due to the preferred misorientation relationship 70°<1120>(∑18 b).It is speculated that these two special misorientation relationships are related to the dislocation type. 展开更多
关键词 Mg alloys ORIENTATION NUCLEATION Quasi-in-situ EBSD Static recrystallization
Biofabrication of aligned structures that guide cell orientation and applications in tissue engineering 认领
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作者 Kejie Lu Ying Qian +5 位作者 Jiaxing Gong Ziyu Zhu Jun Yin Liang Ma Mengfei Yu Huiming Wang 《生物设计与制造(英文)》 SCIE EI 2021年第2期258-277,共20页
The organized alignment of cells in various tissues plays a significant role in the maintenance of specific functions.To induce such an alignment,ideal scaffolds should simulate the characteristics and morphologies of... The organized alignment of cells in various tissues plays a significant role in the maintenance of specific functions.To induce such an alignment,ideal scaffolds should simulate the characteristics and morphologies of natural tissues.Aligned structures that guide cell orientation are used to facilitate tissue regeneration and repair.We here review how various aligned structures are fabricated,including aligned electrospun nanofibers,aligned porous or channeled structures,micropatterns and combinations thereof,and their application in nerve,skeletal muscle,tendon,and tubular dentin regeneration.The future use of aligned structures in tissue engineering is also discussed. 展开更多
关键词 Aligned structures Cell orientation Electrospun nanofibers Channeled structures MICROPATTERNS Tissue engineering
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三国杂传五种叙录 认领
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作者 熊明 《中国海洋大学学报:社会科学版》 2021年第2期127-137,共11页
从建安元年(196年)开始,至魏咸熙二年或晋泰始元年(265年)司马炎代魏,几近七十年的时间,是历史上的三国时期。三国时期的杂传创作,渐趋兴盛,近七十年间产生的杂传作品约有七十余种。其中属于类传者不多,而今尚有佚文存世者,则有《三辅... 从建安元年(196年)开始,至魏咸熙二年或晋泰始元年(265年)司马炎代魏,几近七十年的时间,是历史上的三国时期。三国时期的杂传创作,渐趋兴盛,近七十年间产生的杂传作品约有七十余种。其中属于类传者不多,而今尚有佚文存世者,则有《三辅决录》《汝南先贤传》《海内士品》《海内先贤传》《会稽先贤传》等数部而已,今略加考释叙录。从《三辅决录》等五传所遗文字看,三国时期杂传对人物的传录,已普遍与正史人物列传相区别,表现出自为一体的鲜明特征,在某种意义上,可视为杂传文体自觉意识的体现。 展开更多
关键词 三国杂传 类传五种 叙录 单一化 指向性
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Clarifying the roles of grain boundary and grain orientation on the corrosion and discharge processes of α-Mg based Mg-Li alloys for primary Mg-air batteries 认领
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作者 Huabao Yang Liang Wu +5 位作者 Bin Jiang Wenjun Liu Jiangfeng Song Guangsheng Huang Dingfei Zhang Fusheng Pan 《材料科学技术:英文版》 SCIE EI CAS 2021年第3期128-138,共11页
The corrosion behavior at open circuit potential(OCP)and discharge properties under applied anodic currents of twoα-Mg based Mg-Li alloys,i.e.,LAZ131 and LAZ531,with different microstructural features for primary Mg-... The corrosion behavior at open circuit potential(OCP)and discharge properties under applied anodic currents of twoα-Mg based Mg-Li alloys,i.e.,LAZ131 and LAZ531,with different microstructural features for primary Mg-air batteries are investigated.The results show that the grain boundaries contribute equally to the corrosion and discharge processes,which are attacked preferentially than the grain interiors and accelerate the dissolution processes ofα-Mg based Mg-Li alloys.The(10-10)/(11-20)orientated grains are attacked preferentially than the(0002)orientated grains on the corrosion and discharge process.The increased corrosion rate and improved discharge properties are attributed to the refinement of grain size,decreased content of(0002)orientated grains and increased content of(10-10)/(11-20)orientated grains.Of those,the LAZ531 alloy possesses high and steady discharge voltage at small discharge current density for long time,with the values of 1.4801 V at 2.5 mA cm^(-2)and 1.3742 V at 10 mA cm^(-2). 展开更多
关键词 Grain boundary Grain orientation Corrosion behavior Discharge property Mg-air battery
多级双向拉伸挤出系统在聚合物加工中的应用进展 认领
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作者 李春海 吴宏 +8 位作者 李姜 沈佳斌 熊英 陈蓉 张先龙 郑宇 张捷 刘桂廷 郭少云 《高分子材料科学与工程》 EI CAS 北大核心 2021年第1期349-358,374,共11页
以自主研发的分割-双向拉伸-叠加单元(LME)为核心,借助数学中的积分思想,通过串联一系列的LME,累积单个LME中双向拉伸/剪切力场作用效果,发明一套新型多级双向拉伸挤出系统(MBSE)。分析讨论MBSE构造及原理,介绍MBSE拉伸/剪切复合力场的... 以自主研发的分割-双向拉伸-叠加单元(LME)为核心,借助数学中的积分思想,通过串联一系列的LME,累积单个LME中双向拉伸/剪切力场作用效果,发明一套新型多级双向拉伸挤出系统(MBSE)。分析讨论MBSE构造及原理,介绍MBSE拉伸/剪切复合力场的实现及分布,从纯聚合物、聚合物/聚合物共混材料,聚合物/无机纳米粒子复合材料等物料体系着重讨论了MBSE的特点与优势。研究结果表明,相对于传统的基于单一剪切力场的挤出成型方法,MBSE中的双向拉伸/剪切复合力场,在调控分散相形态、调控聚合物晶体结构、促进纳米填分散及调控纳米填料粒子网络等方面具有突出的优势,在高分子及其复合材料的加工成型中具有广阔的应用前景。 展开更多
关键词 拉伸力场 剪切力场 加工成型 原位成纤 取向 分散
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基于图像处理的爬壁机器人焊缝识别与跟踪 认领
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作者 杨玥旻 闫维新 《机械与电子》 2021年第3期65-68,74,共5页
基于爬壁机器人移动平台和单目相机的图像采集系统,设计了一种焊后焊缝图像处理方法,将改进的自适应中值滤波算法与灰度形态学方法结合,实现从信噪比较高的图像中提取特征。采用基于边缘检测和Hough变换的焊缝位置提取算法,经测试识别... 基于爬壁机器人移动平台和单目相机的图像采集系统,设计了一种焊后焊缝图像处理方法,将改进的自适应中值滤波算法与灰度形态学方法结合,实现从信噪比较高的图像中提取特征。采用基于边缘检测和Hough变换的焊缝位置提取算法,经测试识别准确率达70%,且单幅图像平均处理时间为200 ms,能满足管道爬壁机器人行进过程中的实时焊缝跟踪,并提供了一种引导机器人沿焊缝前进的自主定向方案。 展开更多
关键词 爬壁机器人 图像处理 特征提取 焊缝跟踪 定向
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Visual response characteristics of neurons in the second visual area of marmosets 认领
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作者 Yin Yang Ke Chen +3 位作者 Marcello G.P.Rosa Hsin-Hao Yu Li-Rong Kuang Jie Yang 《中国神经再生研究:英文版》 SCIE CAS 2021年第9期1871-1876,共6页
The physiological characteristics of the marmoset second visual area(V2) are poorly understood compared with those of the primary visual area(V1). In this study, we observed the physiological response characteristics ... The physiological characteristics of the marmoset second visual area(V2) are poorly understood compared with those of the primary visual area(V1). In this study, we observed the physiological response characteristics of V2 neurons in four healthy adult marmosets using intracortical tungsten microelectrodes. We recorded 110 neurons in area V2, with receptive fields located between 8° and 15° eccentricity. Most(88.2%) of these neurons were orientation selective, with half-bandwidths typically ranging between 10° and 30°. A significant proportion of neurons(28.2%) with direction selectivity had a direction index greater than 0.5. The vast majority of V2 neurons had separable spatial frequency and temporal frequency curves and, according to this criterion, they were not speed selective. The basic functional response characteristics of neurons in area V2 resemble those found in area V1. Our findings show that area V2 together with V1 are important in primate visual processing, especially in locating objects in space and in detecting an object's direction of motion. The methods used in this study were approved by the Monash University Animal Ethics Committee, Australia(MARP 2009-2011) in 2009. 展开更多
关键词 direction selectivity electrophysiological recording MARMOSET orientation selectivity receptive field second visual area spatial frequency speed selectivity temporal frequency
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Neurite Orientation Dispersion and Density Imaging of Rat Brain Microstructural Changes due to Middle Cerebral Artery Occlusion at a 3T MRI 认领
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作者 Zhen-xiong WANG Wen-zhen ZHU +2 位作者 Shun ZHANG Mehran Shaghaghi Ke-jia CAi 《当代医学科学(英文)》 SCIE CAS 2021年第1期167-172,共6页
The purpose of this work was to demonstrate the feasibility of neurite orientation dispersion and density imaging(NODDI)in characterizing the brain tissue microstructural changes of middle cerebral artery occlusion(MC... The purpose of this work was to demonstrate the feasibility of neurite orientation dispersion and density imaging(NODDI)in characterizing the brain tissue microstructural changes of middle cerebral artery occlusion(MCAO)in rats at 3T MRI,and to validate NODDI metrics with histology.A multi-shell diffusion MRI protocol was performed on 11 MCAO rats and 10 control rats at different post-operation time points of 0.5,2,6,12,24 and 72 h.NODDI orientation dispersion index(ODI)and intracellular volume fraction(V_(ic))metrics were compared between MCAO group and control group.The evolution of NODDI metrics was characterized and validated by histology.Infarction was consistent with significantly increased ODI and V_(ic)in comparison to control tissues at all time points(P<0.001).Lesion ODI increased gradually from 0.5 to 72 h,while its V_(ic)showed a more complicated and fluctuated evolution.ODI and V_(ic)were significantly different between hyperacute and acute stroke periods(P<0.001).The NODDI metrics were found to be consistent with the histological findings.In conclusion,NODDI can reflect microstructural changes of brain tissues in MCAO rats at 3T MRI and the metrics are consistent with histology.This study helps to prepare NODDI for the diagnosis and management of ischemic stroke in translational research and clinical practice. 展开更多
关键词 diffusion magnetic resonance imaging neurite orientation dispersion and density imaging middle cerebral artery occlusion model stroke rats
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Research on the Relationship between Export Orientation and R&D Investment of China’s Pharmaceutical Industry in Different Regions 认领
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作者 Qiao Jiahui Wang Su Chen Yuwen 《亚洲社会药学》 2021年第1期48-59,共12页
Objective To study the relationship between export orientation and research and development(R&D)investment so as to provide suggestions and references for improving the R&D investment level and innovation capa... Objective To study the relationship between export orientation and research and development(R&D)investment so as to provide suggestions and references for improving the R&D investment level and innovation capabilities of pharmaceutical industry due to the progress of globalization and the continuous development of export trade of China’s pharmaceutical industry.Methods The relevant data of China’s pharmaceutical industry from 2001 to 2016 was selected to establish an error correction model based on the co-integration theory,and then the Granger causality test was conducted to determine the relationship between the export orientation and R&D investment of China’s pharmaceutical industry in different regions.Results and Conclusion It is found that the export orientation of the pharmaceutical industry in different regions has a significant negative impact on the investment of R&D.Among them,the middle region has the greatest impact,followed by the eastern and western regions.The export orientation of the pharmaceutical industry in the middle region has a lag effect on R&D investment,and the lag phase is two years. 展开更多
关键词 pharmaceutical industry export orientation R&D investment co-integration analysis
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全极化昆虫雷达生物参数反演方法与外场定量试验验证 认领
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作者 王锐 李卫东 +2 位作者 胡程 李沐阳 毛华锋 《信号处理》 北大核心 2021年第2期199-208,共10页
全极化雷达是新一代昆虫雷达的发展方向。本文介绍了全极化雷达的昆虫体轴朝向、体重和体长等生物参数反演方法。相对传统方法,这些方法精度更高,然而,这些方法仅经过微波暗室测量昆虫数据验证了可行性,还未经过实际全极化雷达外场测量... 全极化雷达是新一代昆虫雷达的发展方向。本文介绍了全极化雷达的昆虫体轴朝向、体重和体长等生物参数反演方法。相对传统方法,这些方法精度更高,然而,这些方法仅经过微波暗室测量昆虫数据验证了可行性,还未经过实际全极化雷达外场测量验证。本文利用Ku波段全极化昆虫雷达,设计并开展了基于双无人机协同飞行悬吊昆虫的外场定量试验,测量了44只不同体型昆虫在不同朝向下的雷达数据,基于测量数据,成功验证了面向全极化雷达的昆虫生物参数反演方法在实际外场雷达的应用,并分析了测量精度。 展开更多
关键词 全极化昆虫雷达 朝向 体重 体长 外场定量试验
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Influence of bedding structure on stress-induced elastic wave anisotropy in tight sandstones 认领
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作者 Xiaying Li Xinglin Lei +1 位作者 Qi Li Dianguo Chen 《岩石力学与岩土工程学报:英文版》 SCIE 2021年第1期98-113,共16页
To understand the evolution of stress-induced elastic wave anisotropy,three triaxial experiments were performed on sandstone specimens with bedding orientations parallel,perpendicular,and oblique to the maximum princi... To understand the evolution of stress-induced elastic wave anisotropy,three triaxial experiments were performed on sandstone specimens with bedding orientations parallel,perpendicular,and oblique to the maximum principal stress.P-wave velocities along 64 different directions on each specimen were monitored frequently to understand the anisotropy change at various stress levels by fitting Thomsen’s anisotropy equation.The results show that the elastic wave anisotropy is very sensitive to mechanical loading.Under hydrostatic loading,the magnitude of anisotropy is reduced in all three specimens.However,under deviatoric stress loading,the evolution of anisotropic characteristics(magnitude and orientation of the symmetry axis)is bedding orientation dependent.Anisotropy reversal occurs in specimens with bedding normal/oblique to the maximum principal stress.P-wave anisotropyε0 is linearly related to volumetric strain Sv and dilatancy,indicating that stress-induced redistribution of microcracks has a significant effect on P-wave velocity anisotropy.The closure of initial cracks and pores aligned in the bedding direction contributes to the decrease of the anisotropy.However,opening of new cracks,aligned in the maximum principal direction,accounts for the increase of the anisotropy.The experimental results provide some insights into the microstructural behavior under loading and provide an experimental basis for seismic data interpretation and parameter selection in engineering applications. 展开更多
关键词 Elastic wave anisotropy Stress-induced anisotropy Anisotropy reversal Bedding orientation MICROSTRUCTURE Tight sandstone
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取向晶种法制备沸石分子筛膜研究进展 认领
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作者 刘益 刘毅 《高等学校化学学报》 SCIE EI CAS 北大核心 2021年第1期117-132,共16页
近年来沸石分子筛膜因在分离、催化、传感和防腐等研究领域具有重要的应用价值而引起广泛关注.其中,具有优先取向微观结构的沸石分子筛膜由于能够显著降低客体分子在膜内的扩散路径并减少膜内的晶间界缺陷密度,成为膜分离学科的研究重点... 近年来沸石分子筛膜因在分离、催化、传感和防腐等研究领域具有重要的应用价值而引起广泛关注.其中,具有优先取向微观结构的沸石分子筛膜由于能够显著降低客体分子在膜内的扩散路径并减少膜内的晶间界缺陷密度,成为膜分离学科的研究重点.本文以b-轴取向MFI沸石分子筛膜为主线,综述了国内外制备取向沸石分子筛膜的最新研究进展;详细介绍了取向晶种法制膜工艺,侧重总结了MFI沸石纳米片合成、b-轴取向沸石晶种单层制备以及二次生长调控等方面的研究成果;在深入探讨各类取向沸石分子筛膜制备策略的基础上,分析探讨了其中存在的关键问题与解决措施,最后对取向沸石分子筛膜的发展方向进行了展望. 展开更多
关键词 沸石 取向 晶种层 分离
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选区激光熔化技术制备n型Bi2Te2.7Se0.3热电材料工艺、取向性及性能的研究 认领
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作者 武雪峰 鄢永高 唐新峰 《热加工工艺》 北大核心 2021年第2期56-62,共7页
采用选区激光熔化技术制备了n型Bi2Te2.7Se0.3块体样品,并探索了激光工艺参数对材料成形质量、化学组成、微结构、取向性以及热电性能的影响,最终打印出性能与区熔制备材料接近的高致密样品。结果表明,在基板上最开始的若干单层成形过程... 采用选区激光熔化技术制备了n型Bi2Te2.7Se0.3块体样品,并探索了激光工艺参数对材料成形质量、化学组成、微结构、取向性以及热电性能的影响,最终打印出性能与区熔制备材料接近的高致密样品。结果表明,在基板上最开始的若干单层成形过程中,激光体能量密度Ev=33.3~46.67 J/mm3时,样品成形质量较好。当打印厚度超过约0.1 mm时,成形质量出现劣化,可能的原因是打印样品具有较强的取向性,导致其热导率的各向异性以及与基板具有较大的差异,因而影响了成形粉体的熔化和凝固过程。后续打印过程中采用重熔的方法,消除了因热导率变化带来的成形劣化。当打印厚度超过约1 mm时,样品成形质量再次劣化,这是由于样品的厚度已经足够大,基板对成形过程中熔池附近的温度场影响逐渐减小,而主要受打印样品的影响。考虑到打印样品热导的关系,于是进一步改善工艺,提高了激光的体能量密度,最终得到了半径为20 mm、厚度为15 mm的样品。研究了激光成形过程中元素挥发对最终样品化学组成的影响规律,通过调节粉体的初始配比最终得到了组分稳定、性能接近区熔工艺制备的块体材料。 展开更多
关键词 选区激光熔化 n型Bi2Te2.7Se0.3 取向性 热电性能
Efficient Two‑Dimensional Perovskite Solar Cells Realized by Incorporation of Ti_(3)C_(2)T_(x) MXene as Nano‑Dopants 认领
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作者 Xin Jin Lin Yang Xiao‑Feng Wang 《纳微快报:英文版》 SCIE EI CAS 2021年第4期234-246,共13页
Two-dimensional(2D)perovskites solar cells(PSCs)have attracted considerable attention owing to their excellent stability against humidity;however,some imperfectness of 2D perovskites,such as poor crystallinity,disorde... Two-dimensional(2D)perovskites solar cells(PSCs)have attracted considerable attention owing to their excellent stability against humidity;however,some imperfectness of 2D perovskites,such as poor crystallinity,disordered orientation,and inferior charge transport still limit the power conversion efficiency(PCE)of 2D PSCs.In this work,2D Ti3C2Tx MXene nanosheets with high electrical conductivity and mobility were employed as a nanosized additive to prepare 2D Ruddlesden–Popper perovskite films.The PCE of solar cells was increased from 13.69(without additive)to 15.71%after incorporating the Ti_(3)C_(2)T_(x) nanosheets with an optimized concentration.This improved performance is attributed to the enhanced crystallinity,orientation,and passivated trap states in the 3D phase that result in accelerated charge transfer process in vertical direction.More importantly,the unencapsulated cells exhibited excellent stability under ambient conditions with 55±5%relative humidity. 展开更多
关键词 2D perovskite solar cells Ti_(3)C_(2)T_(x)nanosheets Trap densities Vertical orientation Charge transport
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聚乙烯晶体形态及排列方向对其力学性能的影响 认领
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作者 张大合 聂敏 石艳 《塑料工业》 CAS 北大核心 2021年第1期30-33,共4页
采用模压和流延成型工艺,制备了具有各向同性球晶和各向异性串晶结构的聚乙烯(PE)样品,系统研究了晶体形态及串晶排列对PE强度和蠕变性能的影响。结果表明,PE的性能不仅与晶体形态相关,还取决于外加载荷与串晶排列的方向。随着外加载荷... 采用模压和流延成型工艺,制备了具有各向同性球晶和各向异性串晶结构的聚乙烯(PE)样品,系统研究了晶体形态及串晶排列对PE强度和蠕变性能的影响。结果表明,PE的性能不仅与晶体形态相关,还取决于外加载荷与串晶排列的方向。随着外加载荷与串晶排列方向夹角的增大,有效晶片间的系带分子tie分子链数目减少,材料的破坏形式从片晶分离转变为片晶滑移,使得样品的强度和耐蠕变性能显著降低。 展开更多
关键词 聚乙烯 取向 排列方向 蠕变 强度
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文章速递以“扣子论”为切入点的新时代中华武术发展改革定位 认领
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作者 杨建营 《北京体育大学学报》 CSSCI 北大核心 2021年第1期145-156,共12页
为促进新时代中华武术更好地传承发展及服务社会,主要以习近平总书记提出的"扣子论"为切入点,运用文献资料法、专家访谈法、逻辑分析法等研究方法,剖析了60年前中华武术发展因"扣错了第一粒扣子"而造成的种种问题,... 为促进新时代中华武术更好地传承发展及服务社会,主要以习近平总书记提出的"扣子论"为切入点,运用文献资料法、专家访谈法、逻辑分析法等研究方法,剖析了60年前中华武术发展因"扣错了第一粒扣子"而造成的种种问题,进而提出:当务之急是重新扣好中华武术发展的"第一粒扣子"。主要研究结果如下:1)20世纪前期,武术之所以被推上历史舞台,是因为其独特的精神教育价值,当时的武术承担了"铸就中国文化之脊"的重任,"强健身体,培育精神,拯救文化,复兴民族"是当时开展武术的初心和时代赋予武术的使命。2)20世纪中期,在"破旧立新,肃清封建残余"思想影响下,对武术进行了全方位改造,破除了传统武术拳种,摈弃了武术技击对抗,忽略了武术特有的精神教育价值,取而代之的是以"锻炼身体的实用价值"和"树立优美形象"为价值定位而重新创编的以艺术表现为价值取向的"新武术",从而"扣错了新中国武术发展的第一粒扣子"。3)20世纪后期,虽然曾有过"重扣扣子"的努力,但最终半途而废,以至于进入21世纪的中华武术问题重重。根据以上研究结果得出以下结论:1)新时代中华武术要取得全新发展,必须以史为鉴,以邻为鉴,"重新扣好中华武术发展的第一粒扣子",这需要找回百年前开展武术教育的初心,使武术承担起本应承担的使命。2)着眼于中华民族伟大复兴的中国梦,培育青少年的"刚健自强"精神,凝聚中华民族的"精气神"应该是新时代国家层面对中华武术新的价值定位。该研究对于纠正新时代中华武术的发展方向具有一定的现实价值,对于如何使武术的社会价值最大化具有一定的理论意义。 展开更多
关键词 扣子论 中华武术 传承发展 初心 使命 改革 定位
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