制备工艺对BaSnO3粉体特性的影响

用低温烧结法制备了钙钛矿型的BaSnO3纳米晶.通过能谱仪(EDS),X射线衍射仪(XRD)和透射电镜(TEM)对纳米粒子的组成、结构、形貌、粒径进行了表征和分析.分析了不同制备工艺对粉末特征的影响,结果表明:在-30℃陈化24 h,400℃焙烧2 h已经生成了BaSnO3晶粒,而600℃焙烧2 h,制备的粉末纯度较高,粒度较细小且分布均匀.     

NiTi气雾化制粉工艺对选区激光熔化成型性、制件超弹性的影响

选区激光熔化成型具有外界温度感知能力的NiTi形状记忆合金是4D打印金属材料技术的基础研究,根据选区激光熔化技术对粉末性能的要求,研究NiTi形状记忆合金不同气雾化制粉工艺对选区激光熔化成型性及制件超弹性的影响规律具有重要意义。通过对比分析真空惰性气体雾化(VIGA)、电极感应熔炼气雾化(EIGA)制粉工艺对NiTi合金粉末杂质含量、流动性、球形度等性能的影响,发现VIGA制粉工艺由于采用坩埚熔炼,导致合金杂质元素增加、粉体性能恶化,粉末粒度分布偏向细粉侧,极易形成卫星粉,导致粉末流动性差,在打印过程中铺粉困难而难以成型,并且氧含量的增加导致打印过程中易发生球化、开裂等现象,使得VIGA工艺制备的NiTi合金粉末SLM成型性较差。而采用EIGA工艺制备的粉末粒度分布均匀、流动性好、氧含量低,满足选区激光熔化技术对NiTi合金粉末的特性要求。并对比分析两种工艺制备的粉末打印样品的表面形貌,成型了具有完全回复性能的超弹NiTi形状记忆合金样件。     

激光焊接金刚石工具用铁钴预合金粉末的制备与性能

采用共沉淀法制备了用于激光焊接金刚石工具过渡层的铁钴预合金粉末,用X射线衍射仪分析其物相组成,用扫描电镜观察其形貌特征;将预合金粉末进行热压烧结后,对其相对密度、硬度、抗弯强度和焊接性能进行了研究.结果表明:制备的粉末为FeCo(α')相,随烧结温度的升高,烧结试样的相对密度略有增大,而硬度有所下降,抗弯强度变化较小;高温烧结试样的焊接性能优于低温烧结试样,在850℃烧结制备的试样焊接强度达到51.6 N·m.     

Fe-Ti-C 系反应等离子喷涂粉末制备工艺比较

通过对用前驱体热分解/破碎法和喷雾干燥/前驱体热分解工艺(SD/PP)制备3种反应热喷涂粉末及 TiC-Fe复合涂层进行检验证明用喷雾干燥/前驱体热分解(SD/PP)工艺球形粉末制备的涂层具有良好的耐磨性能和综合性能。     

一种改进型的磁流变液制备工艺研究

分别以传统的磁流变液制备工艺和改进的磁流变液制备工艺,以羰基铁粉为软磁性颗粒,以专用减振液为母液,制备了2种磁流变液,并对其零场粘度、悬浮稳定性和剪切屈服强度进行了测试和分析。试验结果表明,改进型工艺制备的磁流变液零场粘度比传统工艺制备的磁流变液稍高,但其沉降稳定性和剪切屈服强度均优于以传统工艺制备的磁流变液。     

热压烧结制备高密度钨铜合金

以用机械合金化法制备的超细W-15Cu复合粉末为原料,采用热压烧结工艺制备了高密度的W-15Cu合金,用扫描电镜、硬度仪、密度测试仪等研究了烧结工艺对合金组织和性能的影响.结果表明:采用高能球磨可以制备出钨晶粒镶嵌铜相中的复合粉末;采用热压烧结,在30MPa、1 500 ℃×2 h的条件下,可以制备出相对密度99.8%、断裂强度1290.6 MPa、硬度44.8HRC的高密度钨铜合金.     

不同粉末对Fe—Ni合金注射成形工艺过程的影响

研究了两种不同粒度和形貌的羰基铁粉对Fe-Ni合金注射成形工艺过程的影响。结果表明：球形度好、粒度小的粉末的混合、制粒、注射成形工艺性能以及其喂料流变性能都好于球形度差、粒度大的粉末,且前者最终产品力学性能也好于后者。     

枪管长度和喷涂距离对超音速火焰喷涂制备纳米WC-12Co涂层组织和硬度的影响

以纳米WC-12Co粉末为喷涂喂料,采用超音速火焰喷涂工艺,在其它喷涂工艺参数优化的条件下,只改变枪管长度和喷涂距离,在Q235钢基体上制备了八种涂层;用X射线衍射仪和扫描电镜对喷涂粉末及涂层进行了相结构和形貌分析,探讨了枪管长度和喷涂距离对涂层显微硬度、相结构以及表面形貌的影响。结果表明：与喷距相比,枪管长度是影响纳米WC涂层显微硬度的主要因素,用长枪管制备的涂层比短枪管制备的涂层分解严重,但相应涂层的显微硬度却显著提高;当枪管长度相同时,喷距变化也会对涂层的相结构、表面形貌和显微硬度产生一定的影响。     

超声场中湿法制备纳米粉末的原理和方法

介绍了超声波在湿法制备纳米粉末中的应用机理，探讨了超声波对纳米颗粒的生成和团聚的影响，综述了超声场下湿法制备纳米粉末常用的方法，同时对超声在纳米材料制备上的应用作了展望。     

一种柔性PVDF压电薄膜传感器的制备方案

利用性能优异的PVDF压电薄膜制备的新型柔性传感器柔性好、适应性强,可适应复杂曲面,其应用前景十分广阔。首先设计了具有柔性基底的PVDF压电薄膜传感器结构;其次,按照实验设计利用PVDF粉末制备了性能良好的PVDF压电薄膜,提出了一种柔性PVDF薄膜传感器的制备方案;最后总结了该传感器实验制备的主要工艺步骤,可为柔性PVDF传感器设计制备提供参考。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.