Dynamic recrystallization during hot torsion of Al-4Mg alloy

Binary Al-4Mg alloy have been deformed by hot torsion at 300-500℃ and strain rates of 0,006-1.587 s-1 to a true strain of 5.5. The specimens were annealed in vacuum for 1.5 h at 500℃ and then water quenched. The study indicates that the dynamic recrystallization occurs during hot torsion of Al-4Mg alloy in a certain range of Z parameter (Zener-Hollmon Parameter), i.e. 19.3 ≤ lnZ ≤ 24.8. Increasing the strain rate at higher deformation temperature or reducing the strain rate at lower deformation temperature accelerates the occurrence of dynamic recrystallization in the alloy.     

Bake hardening behavior of TRIP and DP steels

The bake hardening (BH) behavior of transformation-induced plasticity (TRIP) and dual-phase (DP) steels after different prestrains was studied. The experimental results indicate that TRIP steel exhibits good BH ability while DP steel does not, and prestrain displays a strong effect on the BH values of both steels. The comparison of microstructures of the two steels showed that the hard second phase in the matrix might be harmful to the BH ability. For deformed specimens, baking resulted in a loss of uniform elongation, but there was no obvious decrease in uniform elongation for unprestrained specimens.     

X射线底片焊缝缺陷的支持向量机识别方法

准确识别X射线底片焊缝缺陷类别,可改进焊接工艺、提高焊接质量。该文在分析和比较几种焊缝缺陷识别模式的基础上,提出了基于支持向量机（SVM）的X射线底片焊缝缺陷识别方法。该方法首先对X射线底片进行数字化处理和缺陷特征提取,然后针对X射线底片焊缝缺陷样本特点,建立SVM“一对一”聚类结构并对样本进行识别。实验结果表明,该模型具有识别精度高、速度快、容易实现等优点,适合对X射线底片焊缝缺陷识别。     

Depressing effect of sodium hexametaphosphate on apatite in flotation of rutile

The separation of rutile from apatite by flotation and the mechanism of depressing the apatite of sodium hexametaphosphate were studied. The results showed that rutile and apatite could be separated by using alkyl-imino-bismethylene phosphoric acid and sodium hexametaphosphate as a collector and a regulator, respectively. Sodium hexametaphosphate could selectively dissolve calcium ions on the apatite surface, and make calcium ions break away from lattice binding through combining.     

Densification behavior of high Nb containing TiAl alloys through reactive hot pressing

Densification behavior of high Nb containing TiAl alloys through reactive hot pressing was investigated. The results showed that the density of the sample hot pressed at 1400℃ could reach a near full density of 98.37%. However, the densification abnormality was observed at 1500℃. The diffusion of elemental Nb during microstructural evolution is an important aspect affecting densification, which will form pore nests. With the increase of hot pressing temperature, the diffusion of Nb becomes more adequate. HIP (Hot isostatic pressing) treatment can only decrease porosity to some extent, but cannot eliminate it completely.     

东亚赤道异常区电离层结构与扰动的CT成像

介绍东经 12 0°低纬电离层CT实验及CT重建结果 .提出一种改进的电离层CT算法 .该算法通过联合使用差分Doppler相位和差分Doppler频率数据 ,把相位积分常数估算融入重建过程之中 .CT重建结果发现 ,赤道异常峰电子密度等值线沿磁力线倾斜 ;峰位置逐日变化时 ,倾斜程度也随之改变 ,使峰电子密度等值线仍沿磁力线 ;峰朝赤道的运动通常伴随峰区展宽 .此外 ,对一次中等强度磁暴期间电离层响应的分析发现 ,在赤道异常峰区 ,磁暴急始之后 2 0min出现电子密度的深度耗空 ,这种耗空遍及从底到顶的整个F区 .结果表明 ,电离层CT技术在研究电离层赤道异常的动力过程、电离层行扰和不规则结构的时空演变以及暴时电离层响应等方面具有重要的应用价值与前景 .     

Deformation characterization of conductive particles in anisotropically conductive adhesive simulated by FEM

The deformation behavior and the contact area of conductive particles in anisotropically conductive adhesives (ACA) were investigated by finite element method (FEM). The solid conductive particles are made of pure Ni and Cu. The results indicate that the deformation of the conductive particles is inhomogeneous during fabrication. When the reduction in height is small the deformation concentrates in the area near the contact area. As the reduction in height increases, the strain in the area near the contact area increases, and the metal flows toward the circumference, resulting in the increase of the contact area between the conductive particles and pad. The higher the degree of deformation, the larger the contact area. The regression equations were offered to express the relations between the bounding force and the contact area or the reduction in height. An approach of how to obtain the maximum contact area in ACA was discussed.     

Limit Set Problem of Multi-Agent Systems with Finite States: An Eigenvalue-Based Approach

This paper studies the limit set of multi-agent system with finite states, in which the system is converted into a linear system through an expansion of space. Then, the structure properties of the system matrix are investigated, and the relationships between the eigenvalues and the limit set are developed. As an application, the nilpotent problem of elementary cellular automata(ECA) known as algorithmically undecidable is considered, and all the nilpotent ECA are found out which consists of rules 0, 8, 64, 239, 253, 255.     

Construction and alignment control of the middle steel pylon of Taizhou Bridge

In this paper, the general construction procedure of the steel middle pylon is briefly introduced. The alignment control of the pylon is carried out during the whole process of the construction. The control concept is extended to the manufacture stage. The manufacturing alignment errors are strictly controlled in the segments precast process in factory, and the errors are recognized and predicted precisely during the installation stage. The adjusting joints are employed to amend the accumulated errors, which ensure that the steel pylon alignment could satisfy the precision requirements after installation.