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Ultra‐low cost Ti powder for selective laser melting additive manufacturing and superior mechanical properties associated 预览
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作者 Yuhang Hou Bin Liu +5 位作者 Yong Liu Yinghao Zhou Tingting Song Qi Zhou Gang Sha Ming Yan 《光电进展(英文)》 2019年第5期10-17,共8页
One of the bottleneck issues for commercial scale-up of Ti additive manufacturing lies in high cost of raw material, i.e. the spherical Ti powder that is often made by gas atomization. In this study, we address this s... One of the bottleneck issues for commercial scale-up of Ti additive manufacturing lies in high cost of raw material, i.e. the spherical Ti powder that is often made by gas atomization. In this study, we address this significant issue by way of powder modification & ball milling processing, which shows that it is possible to produce printable Ti powders based on ultra- low cost, originally unprintable hydrogenation-dehydrogenation (HDH) Ti powder. It is also presented that the as-printed Ti using the modified powder exhibits outstanding mechanical properties, showing a combination of excellent fracture strength (~895 MPa) and high ductility (~19.0% elongation). 展开更多
关键词 selective laser melting POWDER modification hydrogenation-dehydrogenation (HDH) TI ball MILLING additive manufacturing
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On Compressible Smooth Viscous Fluids in Slowly Expanding Balls 预览
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作者 Huicheng Yin Lin Zhang 《分析理论与应用:英文刊》 CSCD 2019年第1期28-65,共38页
In[17]and[19,20],the global existence and large time behaviors of smooth compressible fluids(including inviscid gases of Euler equations,viscous gases of Navier-Stokes equations,and rarified gases of Boltzmann equatio... In[17]and[19,20],the global existence and large time behaviors of smooth compressible fluids(including inviscid gases of Euler equations,viscous gases of Navier-Stokes equations,and rarified gases of Boltzmann equation,respectively)have been established in an infinitely expanding ball with a constant expansion speed.This paper concerns with the viscous fluids in a slowly expanding ball.By involved analy-sis on the density function and the weighted energy estimates,we show that the fluid in the slowly expanding ball smoothly tends to a vacuum state and there is no appearance of vacuum in any part of the expansive ball.Our present result is a meaningful supplement to the one in[19]. 展开更多
关键词 COMPRESSIBLE NAVIER-STOKES equations slowly EXPANDING ball weighted energy ESTIMATE global existence
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高速球棒式摩擦试验机的设计与研究 预览
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作者 李安玲 王涛 +2 位作者 张勇 郑博 何强 《机床与液压》 北大核心 2019年第1期66-71,共6页
高速球棒式试验机是在各种摩擦学系统下测定金属材料、非金属材料、机械零件、摩擦磨损性能的精密测试仪器。针对高速球棒式试验机的发展现状及其现有的缺点,设计高速球棒式摩擦试验机的结构。利用SolidWorks三维软件对高速球棒式摩擦... 高速球棒式试验机是在各种摩擦学系统下测定金属材料、非金属材料、机械零件、摩擦磨损性能的精密测试仪器。针对高速球棒式试验机的发展现状及其现有的缺点,设计高速球棒式摩擦试验机的结构。利用SolidWorks三维软件对高速球棒式摩擦试验机进行三维建模,并对其中主要部分的结构功能与作用进行分析。此外通过分析球棒式摩擦试验机摩擦因数的计算方法,计算出高速球棒式摩擦试验机的摩擦因数,同时利用ANSYS Workbench分析软件对球棒与滚球的受力与振动情况进行仿真分析,模拟该实验机在实际工况下的运转情况. 展开更多
关键词 摩擦试验机 仿真 高速 滚球 球棒
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Scaffolds Prepared with Bovine Hydroxyapatite Composites by 3D Printing
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作者 刘康 张祥林 +4 位作者 ZHOU Kui SHI Lei CHEN Zhichao LI Wenchao CHEN Penghua 《武汉理工大学学报:材料科学英文版》 SCIE EI CAS 2019年第1期230-235,共6页
The bovine hydroxyapatite(BHA) was applied to prepare biological tissue engineering scaffolds by the method of extrusion freeforming. To achieve this goal, BHA were added to sodium alginate(SA) solution to form a slur... The bovine hydroxyapatite(BHA) was applied to prepare biological tissue engineering scaffolds by the method of extrusion freeforming. To achieve this goal, BHA were added to sodium alginate(SA) solution to form a slurry system in appropriate proportion. The resulting mixtures were fabricated to be a kind of controllable and porous scaffolds followed with cross-linking in 5% calcium chloride(CaCl2) solution for 24 h. After that, the scaffolds were sintered in air at 1 000, 1 100, 1 200 and 1 300 ℃ for 5 h. Scanning electron microscopy(SEM) and X-ray diffraction(XRD) studies were performed on the scaffolds to analyze its microstructure and constituent. To explore the effect of sintering temperature on scaffolds, the compressive strength, volume shrinkage and water absorptivity of BHA-SA composite scaffolds after sintering were investigated. The research tests indicated the feasibility of applying BHA powder to 3D printing. Besides, the scaffolds sintered in a respectively lower temperature possess much more pores and performed higher water absorptivity, which means better cellular affinity. And scaffolds sintered between 1 100 and 1 200℃ presents higher compressive strength. 展开更多
关键词 BOVINE bone HYDROXYAPATITE ball MILLING SINTERING 3D PRINTING CONTROLLABLE scaffolds
考虑雷诺数和形状影响的坝岸根石水平水流拖曳力系数修正 预览
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作者 兰雁 沈细中 +3 位作者 邹瑞 杨昌明 蒋思奇 罗立群 《农业工程学报》 EI CAS CSCD 北大核心 2019年第5期173-182,共10页
对于水利工程坝岸散抛根石冲揭失稳,水流作用下根石的拖曳力是重要的力学分析参数。该文基于黄河坝岸散抛根石的形状参数特征,利用水槽试验量测球体及不同形状块体受水流作用的水平拖曳力,研究雷诺数、物体形状指标与拖曳力相关关系及... 对于水利工程坝岸散抛根石冲揭失稳,水流作用下根石的拖曳力是重要的力学分析参数。该文基于黄河坝岸散抛根石的形状参数特征,利用水槽试验量测球体及不同形状块体受水流作用的水平拖曳力,研究雷诺数、物体形状指标与拖曳力相关关系及变化规律,明确影响因素,率定双因素影响下块体的拖曳力系数函数。结果表明,水下球体或近似球状物体的拖曳力系数,基本不受水流及物体形态影响,拖曳力系数趋于0.40~0.56;有棱角块体的水流拖曳力系数,块体雷诺数小于3×10^4的影响区域,系数函数呈双曲线趋势变化;块体雷诺数大于3×10^4的影响区域,迎水面宽高比不大于侧立面长高比,拖曳力系数趋于0.80~0.90,迎水面宽高比大于侧立面长高比,拖曳力系数趋于1.00~1.10。进一步通过试验修正了水流作用下不同形态物体的水平拖曳力系数,提出了块体雷诺数、形状参数双因素影响下物体水平拖曳力系数函数,得到了以不同物体来流方向投影响面积为基准的水平拖曳计算公式,经拟合公式的合理性分析与验证,拖曳力系数拟合优度达到0.90以上,平均相对误差为8.7%;修正后拖曳力平均相对误差仅为7.5%,公式计算效果良好,更准确地反映散抛根石的水下受力特征,为分析水下抛石受水流冲击离散形态提供理论依据。 展开更多
关键词 雷诺数 拖曳力系数 根石 形状 球体 块体
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井下圆球运动分析与新型试压体设计 预览
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作者 王乐顶 王怀婧 +2 位作者 陈新海 槐巧双 李晓勇 《探矿工程:岩土钻掘工程》 2019年第5期44-47,共4页
在油、气、水井井下作业中,圆球广泛地应用于管柱试压、坐封和分段(层)压裂等施工作业。为准确计算现场施工时圆球到达设计点时间(即候球时间),通过对圆球运动过程和受力分析得出新的候球时间计算公式,并指出圆球绕流阻力系数、圆球直... 在油、气、水井井下作业中,圆球广泛地应用于管柱试压、坐封和分段(层)压裂等施工作业。为准确计算现场施工时圆球到达设计点时间(即候球时间),通过对圆球运动过程和受力分析得出新的候球时间计算公式,并指出圆球绕流阻力系数、圆球直径、圆球密度和压井液性能等是影响候球时间的关键因素,为优化施工设计提供了依据;同时提出了一种能减少候球和反洗球时间的新型管柱试压体设计构思,为进一步优化施工作业奠定了基础。 展开更多
关键词 井下作业 圆球 候球时间 新型管柱试压体
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Application of MZI Symmetrical Structure With Fiber Balls and Seven-Core Fiber in Microdisplacement Measurement
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作者 Hong LI Yanming SONG +1 位作者 Mingli DONG Lianqing ZHU 《光子传感器:英文版》 EI CAS CSCD 2019年第2期97-107,共11页
An optical fiber microdisplacement sensor based on symmetric Mach-Zehnder interferometer (MZI) with a seven-core fiber and two single-mode fiber balls is proposed. The rationality and manufacturing process of the MZI ... An optical fiber microdisplacement sensor based on symmetric Mach-Zehnder interferometer (MZI) with a seven-core fiber and two single-mode fiber balls is proposed. The rationality and manufacturing process of the MZI sensing structure are analyzed. The fabrication mechanism of the Mach-Zehnder sensor by CO2 laser is described in detail. Experimental results show that temperature sensitivities of the two dips are 98.65 pm/℃ and 89.72pm/℃, respectively. The microdisplacement sensitivities are 2017.71 pm/mm and 2457.92 pm/mm, respectively. The simultaneous measurement of temperature and microdisplacement is demonstrated based on the sensitive matrix. The proposed Mach-Zehnder interference sensor exhibits the advantages of compact structure, simple manufacturing process, and high reliability. 展开更多
关键词 Microdisplacement Mach-Zehnder interferometer FIBER ball SYMMETRICAL STRUCTURE seven-core FIBER
Influence of Microstructures on Thermal Shock and Sintering Behavior of YSZ-based Thermal Barrier Coatings 预览
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作者 Kirsten Bobzin Lidong Zhao +1 位作者 Mehmet Ote Tim Konigstein 《表面技术》 EI CAS CSCD 北大核心 2019年第4期28-33,共6页
In this study, two thermal barrier coatings based on YSZ were produced by using a commercially available agglomerated and sintered powder and a special spray powder prepared by high energy ball milling. Both thermal b... In this study, two thermal barrier coatings based on YSZ were produced by using a commercially available agglomerated and sintered powder and a special spray powder prepared by high energy ball milling. Both thermal barrier coatings exhibited similar overall porosities, but significantly different microstructures. Application of the special spray powder prepared by high energy ball milling led to a microstructure with numerous inclusions of semi-molten agglomerates, which introduced a plethora of clusters of fine pores into the coating and several more microstructural defects. This microstructure resulted in a significantly better thermal shock behavior compared to the conventional thermal barrier coating. The heat treatment of both thermal barrier coatings atθ=1150℃for t=100 h led to a sintering of both coatings. The results were reduced overall porosity and significantly increased fracture toughness. A correlation between the fracture toughness of both coatings after the heat treatment and the thermal shock life time could not be identified. 展开更多
关键词 THERMAL barrier coating ZrO2-7%Y2O3 high energy ball MILLING THERMAL shock
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Augmented hydrogen production by gasification of ball milled polyethylene with Ca(OH)2 and Ni(OH)2
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作者 Giovanni Cagnetta Kunlun Zhang +2 位作者 Qiwu Zhang Jun Huang Gang Yu 《中国环境科学与工程前沿:英文版》 SCIE EI CAS CSCD 2019年第1期119-127,共9页
Polymer thermal recycling for hydrogen production is a promising process to recover such precious element from plastic waste. In the present work a simple but efficacious high energy milling pretreatment is proposed t... Polymer thermal recycling for hydrogen production is a promising process to recover such precious element from plastic waste. In the present work a simple but efficacious high energy milling pretreatment is proposed to boost H2 generation during polyethylene gasification. The polymer is comilled with calcium and nickel hydroxides and then it is subjected to thermal treatment. Results demonstrate the key role played by the calcium hydroxide that significantly ameliorates hydrogen production. It reacts in solid state with the polyethylene to fonn directly carbonate and hydrogen. In this way, the CO2 is immediately captured in solid fonn, thus shifting the equilibrium toward H2 generation and obtaining high production rate (>25 L/mol CH2). In addition, high amounts of the hydroxide prevent excessive methane fonnation, so the gas product is almost pure hydrogen (~95%). 展开更多
关键词 Hydrogen production GASIFICATION Plastic waste High energy ball MILLING
Modeling and Experiment on Contact Stiffness and Accuracy Analysis of Ball Linear Guide Feed Unit 预览
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作者 Wei Zhang Min Wang Bingbing Le 《哈尔滨工业大学学报:英文版》 EI CAS 2019年第1期30-41,共12页
The contact stiffness and the error analysis have an important effect on the manufacture and the optimization of Ball Linear Guide Feed Unit (BLGFU). In order to analyze the contact stiffness and linear errors or angl... The contact stiffness and the error analysis have an important effect on the manufacture and the optimization of Ball Linear Guide Feed Unit (BLGFU). In order to analyze the contact stiffness and linear errors or angle errors of BLGFU, in this paper, the contact stress and deformation mechanics between the ball and rail is analyzed. Based on Hertz theory of contact and theory of the multi-body system, a model of the contact stiffness considering the changes in contact angle is established. With the increasing of the external load, the varying trend of the contact deformation can be obtained. Therefore, the motion accuracy degradation of the BLGFU can be analyzed. By using a special experimental device and test system of the rolling linear guide worktable, the horizontal contact stiffness and the vertical linear stiffness are obtained, respectively. By comparing the contact stiffness of the experiment dates and the simulation results, the variation tendency of two curves is consisted and the difference between the measured values and the theoretical values is less than 18%. It is obvious that the model of the contact stiffness considering changes of contact angle has accuracy and feasibility. Thus, while external force point locating at different positions;the contact stiffness and the accuracy analysis of the BLGFU are proved validity by simulations. 展开更多
关键词 BALL linear guide FEED UNIT HERTZ CONTACT theory CONTACT STIFFNESS accuracy analysis
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《摇滚学校》中的冲突、和解与救赎 预览
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作者 郑心玉 《歌剧》 2019年第4期90-93,共4页
曾经在大卫·波尔(David Ball)所著的《了如指掌:阅读戏剧的技术手册》(Backwards and Forwards: A Technical Manualfor Reading Plays ,1983)中读到,戏剧都是由冲突所构成的。在读一个剧本的时候,首先就是要对其中的冲突、解决冲... 曾经在大卫·波尔(David Ball)所著的《了如指掌:阅读戏剧的技术手册》(Backwards and Forwards: A Technical Manualfor Reading Plays ,1983)中读到,戏剧都是由冲突所构成的。在读一个剧本的时候,首先就是要对其中的冲突、解决冲突和新的冲突保持敏感。我承认在第一次看到《摇滚学校》(School of Rock )的剧情时,我对这个风格的戏剧带有一定的偏见。 展开更多
关键词 冲突 学校 摇滚 救赎 和解 技术手册 BALL 戏剧
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New characterizations of Musielak-Orlicz-Sobolev spaces via sharp ball averaging functions
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作者 Sibei YANG Dachun YANG Wen YUAN 《中国数学前沿:英文版》 SCIE CSCD 2019年第1期177-201,共25页
We establish a new characterization of the Musielak-Orlicz-Sobolev space on ?n, which includes the classical Orlicz-Sobolev space, the weighted Sobolev space, and the variable exponent Sobolev space as special cases, ... We establish a new characterization of the Musielak-Orlicz-Sobolev space on ?n, which includes the classical Orlicz-Sobolev space, the weighted Sobolev space, and the variable exponent Sobolev space as special cases, in terms of sharp ball averaging functions. Even in a special case, namely, the variable exponent Sobolev space, the obtained result in this article improves the corresponding result obtained by P. H?st? and A. M. Ribeiro [Commun. Contemp. Math., 2017, 19: 1650022] via weakening the assumption f ∈ L^1(R^n) into f ∈ L^1loc(R^n), which was conjectured to be true by Hosto and Ribeiro in the aforementioned same article. 展开更多
关键词 Musielak-Orlicz-Sobolev SPACE Orlicz-Sobolev SPACE variable EXPONENT Sobolev SPACE SHARP BALL AVERAGING function
Cavity formation in cross-wedge rolling processes
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作者 Zbigniew Pater Janusz Tomczak Tomasz Bulzak 《钢铁研究学报:英文版》 SCIE EI CAS CSCD 2019年第1期1-10,共10页
The problem of end-face cavity formation in parts produced by cross-wedge rolling was studied in order to reduce material consumption.The cavity depth was measured by the displacemern method.Twenty-one different cases... The problem of end-face cavity formation in parts produced by cross-wedge rolling was studied in order to reduce material consumption.The cavity depth was measured by the displacemern method.Twenty-one different cases of rolling were analysed by finile element method to determine the effects of process parameters such as the wedge tool angle,the temperature of material,the tool velocity and the reduction ratio on the depth of end-face cavities.Relationships between these parameters are examined in order to establish depe ndencies enabling quick and simple selection of a con cavity allowance in order to remove the cavities.The equations for calculating the con cavity allowance were verified in an experimental process for manufacturing ball pins with the use of flat tools.Rolling tests were performed using a billet with its length selected in compliance with the established dependencies.The experimental results demonstrate that the proposed solution is a viable method for end-face cavity removal. 展开更多
关键词 Cross-wedge ROLLING End-face CAVITY CONCAVITY ALLOWANCE BALL pin
Thermal Conductivity and Tensile Properties of Carbon Nanofiber-Reinforced Aluminum-Matrix Composites Fabricated via Powder Metallurgy: Effects of Ball Milling and Extrusion Conditions on Microstructures and Resultant Composite Properties
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作者 Fumio Ogawa Shuji Yamamoto Chitoshi Masuda 《金属学报:英文版》 SCIE EI CAS CSCD 2019年第5期573-584,共12页
Carbon nanofiber(CNF)-reinforced aluminum-matrix composites were fabricated via ball milling and spark plasma sintering(SPS), SPS followed by hot extrusion and powder extrusion. Two mixing conditions of CNF and alumin... Carbon nanofiber(CNF)-reinforced aluminum-matrix composites were fabricated via ball milling and spark plasma sintering(SPS), SPS followed by hot extrusion and powder extrusion. Two mixing conditions of CNF and aluminum powder were adopted: milling at 90 rpm and milling at 200 rpm. After milling at 90 rpm, the mixed powder was sintered using SPS at 560℃. The composite was then extruded at 500℃ at an extrusion ratio of 9. Composites were also fabricated via powder extrusion of powder milled at 200 rpm and 550℃ with an extrusion ratio of 9(R9) or 16(R16). The thermal conductivity and tensile properties of the resultant composites were evaluated. Anisotropic thermal conductivity was observed even in the sintered products. The anisotropy could be controlled via hot extrusion. The thermal conductivity of composites fabricated via powder extrusion was higher than those fabricated using other methods. However, in the case of specimens with a CNF volume fraction of 4.0%, the thermal conductivity of the composite fabricated via SPS and hot extrusion was the highest. The highest thermal conductivity of 4.0% CNF-reinforced composite is attributable to networking and percolation of CNFs. The effect of the fabrication route on the tensile strength and ductility was also investigated. Tensile strengths of the R9 composites were the highest. By contrast, the R16 composites prepared under long heating duration exhibited high ductility at CNF volume fractions of 2.0% and 5.0%. The microstructures of composites and fracture surfaces were observed in detail, and fracture process was elucidated. The results revealed that controlling the heating and plastic deformation during extrusion will yield strong and ductile composites. 展开更多
关键词 Al composite Carbon NANOFIBER Ball MILLING Hot EXTRUSION Microstructure and performance
Experimental Evaluation of A New Developed Algorithm for An Autonomous Surface Vehicle and Comparison with Simulink Results 预览
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作者 Hossein MOUSAZADEH Ali KIAPEY 《中国海洋工程:英文版》 SCIE EI CSCD 2019年第3期268-278,共11页
Performing repeatable duties automatically was the dreams of human being for centuries. Although full autonomy has long been dreamed of by visionaries, many researches have been performed for surface vehicles automati... Performing repeatable duties automatically was the dreams of human being for centuries. Although full autonomy has long been dreamed of by visionaries, many researches have been performed for surface vehicles automation since the last century to get close to this dream stepwise. To increase daily working hours and accuracy and reduce cost, operations such as hydrography are susceptible for autonomy. Beside platform topology, installed sensors and energy resources, the core elements of any autonomous surface vehicle are navigation, guidance and control systems. To perform bathymetry operation in autonomy manner, a reliable and robust navigation algorithm is designed and embedded in an autonomous surface vehicle titled Morvarid. Morvarid is a plug-in hybrid solar powered catamaran boat. The developed algorithm is a combination of extended Kalman filter, search ball and potential field approaches. Many experimental field tests are carried out after simulation in Simulink environment. Test results illustrated the algorithm and improved the path followed by reducing SD and RMSE and there is a good correlation between simulation run and experimental tests. 展开更多
关键词 AUTONOMOUS surface vehicle extended KALMAN filter SEARCH ball TRAJECTORY tracking BATHYMETRY
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Microstructure evolution and interface structure of Al-40 wt% Si composites produced by high-energy ball milling
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作者 Yuanyuan Chen Zhangping Hu +5 位作者 Yifei Xu Jiangyong Wang Peter Schützendübe Yuan Huang Yongchang Liu Zumin Wang 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第4期512-519,共8页
High silicon content Al-Si composites with a composition of Al-40 wt% Si were fabricated via a highenergy ball milling method. The microstructure evolution of Al-40 wt% Si milled powders and sintered composites has be... High silicon content Al-Si composites with a composition of Al-40 wt% Si were fabricated via a highenergy ball milling method. The microstructure evolution of Al-40 wt% Si milled powders and sintered composites has been thoroughly studied by scanning electron microscopy, X-ray diffraction, energydispersive spectrometry and high-resolution transmission electron microscopy. The mechanism of ball milling Al-40 wt% Si powders has been disclosed in detail: fracture mechanism dominating in the early stages, followed by the agglomeration mechanism, finally reaching the balance between the fragments and the agglomerates. It has been found that the average particle sizes of mixed Al-Si powders can be refined to the nanoscale, and the crystallite sizes of Al and Si have been reduced to 10nm and 62nm upon milling for 2h–50h, respectively. The finally formed Al-Si interfaces after ball milling for 50h are wellcohesive. A dense and homogenous Al-40 wt% Si composite have been achieved by solid-state sintering at550?C. The results thus provide an effective support for producing bulk nanostructured Al-Si composites. 展开更多
关键词 AL-SI COMPOSITES Interface structure HIGH-ENERGY ball MILLING NANOCRYSTALLINE powders
Performance Training with or without Ball: A Comparison between Helgerud Method in Female Soccer 预览
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作者 Riccardo Izzo Giancarlo Carnevali Ciro Hosseini Varde'i 《运动科学:英文版》 2018年第2期103-107,共5页
关键词 AEROBIC FITNESS women SOCCER VO2MAX HEART rate Helgerud BALL
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皮球集流式阻抗找水仪的改进 预览
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作者 姜海岩 《石油管材与仪器》 2018年第4期35-37,43共4页
皮球集流式阻抗找水仪在下井过程中皮球容易被磨破或是在集流过程中容易被打爆,在测试过程中经常由于井内出沙导致涡轮沙卡等原因导致测试的成功率低。对皮球集流式阻抗找水仪进行了改进,改变了皮球的材质、涡轮的尺寸、传感器电极筒... 皮球集流式阻抗找水仪在下井过程中皮球容易被磨破或是在集流过程中容易被打爆,在测试过程中经常由于井内出沙导致涡轮沙卡等原因导致测试的成功率低。对皮球集流式阻抗找水仪进行了改进,改变了皮球的材质、涡轮的尺寸、传感器电极筒内径。通过实验对比,改进后的新皮球集流式阻抗找水仪解决了皮球容易磨破、打爆和沙卡的问题,传感器电极筒内径的改变,使启动排量得以降低。 展开更多
关键词 阻抗找水仪 集流式 皮球 传感器
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一种偏心球芯加工工艺 预览
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作者 曹宜军 尚洪宝 刘平 《仪器仪表用户》 2018年第8期57-58,共2页
论述了一种运用在超低温球阀上且流道偏心的球芯其加工难点及解决方案,提出了一种可行性加工工艺。
关键词 超低温 偏心流道 球芯 加工
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Units 5-9重点句型大阅兵
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作者 周逸燃 《考试与评价(英语七年级专刊)》 2018年第12期12-13,共2页
Unit 5 Do you have a soccer ball? 1.—Do you have a ping-pong ball?你有乒乓球吗?—Yes,I do.是,我有。/No,I don’t.不,我没有。2.Tom doesn’t have a soccer ball.汤姆没有足球。3.Let’s play tennis.让我们打网球吧。4.That s... Unit 5 Do you have a soccer ball? 1.—Do you have a ping-pong ball?你有乒乓球吗?—Yes,I do.是,我有。/No,I don’t.不,我没有。2.Tom doesn’t have a soccer ball.汤姆没有足球。3.Let’s play tennis.让我们打网球吧。4.That sounds good.那听起来真好。 展开更多
关键词 重点句型 大阅兵 HAVE BALL PLAY That GOOD 乒乓球
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