Restraint of mid-spatial frequency error in magneto-rheological finishing (MRF) process by maximum entropy method

In order to restrain the mid-spatial frequency error in magnetorheological finishing (MRF) process, a novel part-random path is designed based on the theory of maximum entropy method (MEM). Using KDMRF-1000F polishing machine, one flat work piece (98 mm in diameter) is polished. The mid-spatial frequency error in the region using part-random path is much lower than that by using common raster path. After one MRF iteration (7.46 min), peak-to-valley (PV) is 0.062 wave (1 wave =632.8 nm), root-mean-square (RM...     

Combinatorics‐based estimation of reachable states for the system of simple sequential process with resources

The system of simple sequential processes with resources (S³PR) is a class of Petri nets that can model a typical class of resource allocation systems. This paper proposes a method to calculate the number of reachable states of an S³PR. First of all, an upper bound of reachable states of an S³PR can be obtained by combinatorics. The number of unreachable states may be counted in the upper bound because of the existence of shared resources. Hence, the next step is to subtract the number of unreachable states from the upper bound. Here, siphons with two resources derived from resource circuits are used to obtain the number of the unreachable states. The resulting number after subtracting the number of unreachable states from the upper bound is what we are looking for. Finally, example calculations and analyses are conducted to verify the effectiveness of the method. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

“材料成型”专业综合实验教学改革的初探

文章论述了“材料成型”专业综合实验的一种新方案及其特色与实施效果。     

回转窑液压挡轮的应力强度与疲劳断裂分析

运用有限元技术对一台大型沥青焦回转窑设备中发生断裂事故的液压挡轮部件进行强度失效分析及疲劳寿命估算.通过断口形貌分析和金相实验,得出失效机理为疲劳断裂的定性结论.利用Ansys软件建立挡轮的有限元模型,计算出应力和变形等一系列结果.在确定交变应力幅值及裂纹尖端应力强度因子的基础上,利用Paris公式预算含缺陷挡轮的疲劳寿命.在选材及造型设计上对挡轮提出改进方案,将韧性较差的铸钢材料替换为韧性较好的锻钢材料,并优化挡轮轮辐减重孔直径,提高挡轮的疲劳寿命,从而在强度及韧性上均达到最优.设计长期交变应力状态下的工件必须兼顾材料的强度、韧性及其造型优化,这一结论对各类动态承载机械零部件的设计均具有参考价值.     

Variations of the relativistic electron flux after a magnetospheric compression event

On January 21, 2015, a sharp increase of the solar wind dynamic pressure impacted the magnetosphere. The magnetopause moved inward to the region L 8 without causing a geomagnetic storm. The flux of the relativistic electrons in the outer radiation belt decreased by half during this event based on the observations of the particle radiation monitor(PRM) of the fourth of the China-Brazil Earth Resource Satellites(CBERS-4). The flux remained low for approximately 11 d; it did not recover after a small magnetic storm on January 26 but after a small magnetic storm on February 2. The loss and recovery of the relativistic electrons during this event are investigated using the PRM data, medium-and high-energy electron observations of NOAA-15 and the Van Allen Probes, medium-energy electron observations of GOES-13, and wave observations of the Van Allen Probes. This study shows that the loss of energetic electrons in this event is related to magnetospheric compression. The chorus waves accelerate the medium-energy electrons, which causes the recovery of relativistic electrons. The Van Allen Probes detected strong chorus waves in the region L =3–6 from January 21 to February 2. However, the flux of medium-energy electrons was low in the region. This implies that the long-lasting lack of recovery of the relativistic electrons after this event is due to the lack of the medium-energy"seed" electrons. The medium-energy electrons in the outer radiation belt may be a clue to predict the recovery of relativistic electrons.     

Frequency-domain analysis of computer-controlled optical surfacing processes

Mid-high spatial frequency errors are often induced on optical surfaces polished by computer-controlled optical surfacing (CCOS) processes. In order to efficiently remove these errors, which would degrade the performances of optical systems, the ability of a CCOS process to correct the errors have been investigated based on the convolution integral model in view of the availability of material removal. To quantify the ability, some conceptions, such as figure correcting ability and material removal availability (MRA), have been proposed. The research result reveals that the MRA of the CCOS process to correct a single spatial frequency error is determined by its tool removal function (TRF), and it equals the normalized amplitude spectrum of the Fourier transform of its TRF. Finally, three sine surfaces were etched using ion beam figuring (IBF), which is a typical CCOS process. The experimental results have verified the theoretical analysis. The employed method and the conclusions of this work provide a useful mathematical basis to analyze and optimize CCOS processes. Supported by the National Basic Research Program of China (“973” Project) and the National Natural Science Foundation of China (Grant No. 50775215)     

大型回转窑筒体结构的力学行为分析

运用理论分析和有限元技术,研究复杂重载、多支承、变刚度和超静定的大型回转窑筒体结构力学行为。基于超静定连续梁模型和赫兹理论,计算筒体支撑与摩擦载荷以及轮带与托轮的接触压力和面积,为筒体有限元建模提供边界条件。综合考虑多个附件对筒体载荷与刚度的复杂影响。通过定义当量密度等效处理重力载荷。由于耐火砖层的松散堆砌特点,在含耐火砖筒体模型中,若将耐火砖作为整体赋以砖块刚度与实际不符,故将弹性模量赋以小值,以减弱其刚度影响。首次解析推导出耐火砖对筒体的压力分布公式,建立效率更高、不含耐火砖的函数加载筒体模型。两种模型相互验证地分析筒体的变形和应力状态,并与文献中同类回转窑的应力结果接近。结果表明,回转转矩和摩擦阻力对筒体变形及应力的影响很小;筒体应力最高和横截面圆度最差的薄弱部位均在中间档支承处,解释了掉碎砖现象和潜在安全问题的发生机理,且与该窑体的维护记录相符。文中分析方法和结果对回转窑筒体的安全评估、补强设计和窑线调整均有参考价值。     

用于电线电缆的阻燃PVC材料的研究

研究了用于电线电缆的阻燃聚氯乙烯(PVC)的配方设计,通过改变三氧化二锑(Sb2O3),氢氧化铝(ATH)以及硼酸锌的用量,考察材料的燃烧性能和力学性能,确定三种阻燃剂的在该配方体系中的最优化组合。研究表明:在当前配方体系中,Sb2O3的阻燃效果显著,添加分数在6份时效果最佳;ATH在配方体系中同时有阻燃和消烟的作用,但高添加量时,材料的力学性能下降,其添加分数在40份时综合性能较好;硼酸锌有良好的协同阻燃性,能优化Sb2O3存在的配方体系的阻燃性能。     

固态混合电势气体传感器的原理和应用

由于日益严格的排放法规,固态混合电势传感器将成为汽车尾气控制和环境气体检测必不可少的传感器.本文介绍了此类传感器结构和混合电势传感器的工作原理和应用.