某新型X光管轴承内轴断裂分析

X光管是用来产生X射线的主要元件,轴承是X光管的关键器件之一。由轴身和法兰焊接而成的轴承内轴发生断裂。采用对断裂的轴承内轴进行了金相分析、断口检验、硬度检测及焊接质量检验,以揭示其断裂的原因。结果表明:轴身与法兰没有焊透,且焊缝有裂纹,导致其断裂。提出了几点关于预防轴承内轴断裂的建议。     

一种用于车辆图像分割的MSSA-UNet模型

针对实际交通场景下的车辆图像分割方法存在模糊、效果差的问题,本文以UNet神经网络模型为基础,提出了一种融合多尺度模块和空间注意力机制的MSSA-UNet模型。在编解码阶段,采用空洞卷积构建多尺度模块,改善卷积层感受野大小受限的同时输出包含多尺度的特征信息。在上采样前,引入空间注意力机制来弥补采样过程中的局部信息丢失问题,提高特征还原能力。结合交叉熵损失与Dice损失,优化网络学习和训练过程,提高模型的分割精度。实验结果表明,本文提出的MSSA-UNet模型对于车辆图像分割任务在IoU评价指标达到83.48%,较改进前准确度提升了2.28%,模型预测值和真实值更接近,分割效果更好,有效提升了模型的分割性能。     

Inter-dependence of grain growth,Nb segregation,and chemical ordering in FeSiNb nanocrystals

It is known that small Nb additions help stabilize Fe₃Si against grain growth. We studied the microstructural stability of (Fe₃Si)_.95Nb_0.5 during annealing by Mössbauer spectrometry, x-ray diffractometry, and transmission electron microscpy. We measured the development of grain growth, chemical ordering, and the segregation of Nb atoms. We identified inter-relationships between these processes. Chemical ordering was found to be linked to Nb segregation; after the segregation of Nb atoms, DO₃ chemical order developed in the Fe₃Si crystallites. Grain growth was found to be impeded when Nb segregation occurred, although the development of DO₃ order could be involved.     

On the modelling of near tip processes in hydraulic fractures

This paper presents an analysis of the near tip processes which control the pressure distribution of a hydraulic fracture. It is first shown that, if one assumes that the fluid reaches the tip of the fracture, a particular singularity in the pressure and in the stress field develops at the crack tip. This behaviour is only valid if the influence of fracture toughness can be neglected. In practice, the fluid typically does not penetrate up to the tip and a fluid lag develops. It is demonstrated that the existence of a fluid lag does not invalidate the singular solution in a large portion of the fracture and furthermire that the influence of the fracture toughness is negligible when a fluid lag develops. The role of non-linear behaviour at the fracture tip is also analysed. It is shown that, although non-linearity of the rock response significantly affects the pressure response near the crack tip, its influence on the global pressure response is normally negligible. On the other hand, large scale plasticity significantly influences the fracture volume.     

等温松弛电流法在高压电力设备绝缘老化状态评估中的应用

等温松弛电流（IRC）法由于可有效评估多种电气设备的老化状态,因此在高压电气设备绝缘老化状态评估中被广泛应用。首先,介绍了IRC的基本测试原理及其在不同电气设备绝缘老化评估中的应用;然后,根据各电气设备绝缘老化类型,整理并总结了利用IRC对设备绝缘老化进行评估的适用范围;最后,对电力设备绝缘老化评估方面亟需解决的问题及未来的研究方向进行了展望。     

Methodological approach to manufacturing simulation software selection

A growing increase in the use of simulation for the analysis of manufacturing systems has resulted in a rise in the number of both general purpose and application oriented simulation software products. As simulation software selection is often costly and time consuming, the need for a structured approach to software selection is apparent. This paper presents a methodology for simulation software selection in the form of the actions to be taken and factors to be considered during the evaluation and selection of simulation software. Such an approach, when appropriately applied, should result in more effective simulation software selection and application.     

High reversible capacity carbon-lithium negative electrode in polymer electrolyte

Cabonaceous materials from different types are used in polymer electrolyte-based lithium cells in order to evaluate their electrochemical performance during lithium storage in the application as the negative electrode in lithium-ion-type batteries. The formation of a passivating film during the first cathodic polarization may account for the low faradaic yield of the first cycle. It also plays an important role in the stabilization of the carbon/polymer electrolyte interface. Non-graphitized mesocarbon micro beads lead to a higher reversible capacity of 410 mAh/g than the graphitized one. It is suggested that lithium could be reversibly stored as a multilayer ‘deposit’ at the carbon surface. A model of epitaxial lithium electroplating is presented.     

高隔离度双极化微带贴片天线的设计

对双极化方形微带贴片天线端口之间的隔离作了理论与实验研究.基于腔模理论,直观地分析了高次模的激励影响单元两极化端口之间的隔离,并解释了反相馈电抑制其端口耦合的原理.设计、加工了一种新型的双极化微带贴片单元,理论仿真与实验测试结果吻合得很好,证实了应用该方法可使单元两极化端口间的隔离度提高约10～20dB.