Kinetic analysis and strain-compensated constitutive models of Ti-42.9Al-4.6Nb–2Cr during isothermal compression

The hot deformation behavior of Ti-42.9Al-4.6Nb–2Cr (at. %) was investigated by isothermal compression tests at the deformation temperature range of 1373–1573 K, strain rate range of 0.001–1.0 s⁻¹, up to the strain of 0.69. The flow stress test results of Ti-42.9Al-4.6Nb–2Cr showed negative temperature and positive strain rate sensitivity. Besides, strain had a great effect on the hot deformation behavior of Ti-42.9Al-4.6Nb–2Cr. Kinetic analysis was adopted to assess the hot workability of Ti-42.9Al-4.6Nb–2Cr via apparent activation energy (Q) of hot deformation, strain-rate sensitivity index (m) and strain hardening index (n). The Q value varied from 607.1 ± 0.7 kJ·mol⁻¹ to 512.6 ± 10.8 kJ mol⁻¹ with the increasing of strain from 0.1 to 0.6. The effect of strain on the Q value at the deformation temperatures below 1473 K was mainly related to dynamic recrystallization of γ phase and kinking of γ lamellae, while the Q value at the deformation temperature above 1473 K might be linked to γ→α phase transformation and DRV of α phase. Based on the kinetic analysis, strain-compensated Arrhenius model and Hensel-Spittel model were successfully established to predict the hot workability (flow stress). Average absolute relative errors of established strain-compensated Arrhenius model and Hensel-Spittel model were 7.52% and 11.95%, respectively. Moreover, both established constitutive models can be extrapolated for predicting the flow stress of Ti-42.9Al-4.6Nb–2Cr to larger strain levels.     

埋地热油管道停输温降的CFD模拟

针对埋地热油管道的停输温降过程,分别建立了埋地热油管道的物理模型和数学模型,并应用FLUENT软件模拟了不同土壤导热系数、不同大气温度下的温度场分布。同时在稳态的基础上模拟非稳态,得出停输后温度场、速度场的分布。并对不同油温下的温度分布进行模拟,得出了温度场在不同条件影响下的分布规律。对于优化管道建设和制定科学合理的热油输送工艺具有重要的作用。     

某不规则钢框架结构设计与对比分析

结合某一有特色的不规则钢框架结构滑道,开展了2榀不等跨的二维钢框架设计,给出热轧圆钢管材料、截面选取及荷载统计,采用有限元软件ANSYS对结构的内力和变形进行了计算,并与相应规范进行了对比,均满足规范要求,最后给出了相应构造措施,为今后同类工程的设计提供参考。     

夏热冬冷地区相变外墙房间夏季舒适性研究

以典型的夏热冬冷地区气候条件为例,建立焓法数学模型计算相变传热过程,并通过实验证明数学模型的可行性。用数学模型计算相变石膏板放置于建筑外墙对室内温度的影响,对比普通房间进行分析。结果表明,外墙使用相变石膏板的房间温度波动小于普通房间,结合经济型考虑,当相变石膏板相变温度为28℃、相变潜热为80 kJ/kg时,房间的舒适性最佳。     

热水俗预处理对马蹄莲初代培养过程中污染的控制

以生年生长于潮湿土壤中易污染的马莲块茎上的小球为试材,对其进行不同温度的水浴预处理,在初代培养中采取紧封口和松封口对其进行培养,结果表明：不同温度的水浴处理都可不同程度地降低材料的污染,以48℃的温度处理效果最好,污染率控制到了较低水平,且对材料没有副作用,初代培养中对材料进行紧封口和松封口,发现材料的生长状况没有什么差别。     

基于改进Faster R-CNN的行人检测算法

针对行人检测中复杂环境,提出一种改进Faster R-CNN的行人检测算法,使用深度卷积网络从图片中提取适合检测目标的特征。基于Faster R-CNN算法,以Soft-NMS算法代替传统NMS算法,加强Faster R-CNN算法对重叠区域的识别能力。同时,算法通过"Hot Anchors"代替均匀采样的锚点避免大量额外计算,提高检测效率。最后,将21分类问题的Faster R-CNN框架,修改成适用于行人检测的2分类检测框架。实验结果表明:改进Faster R-CNN的行人检测算法在VOC 2007行人数据集,检测效率和准确率分别提升33%、2.6%。     

金刚石纳米粉引晶方法制备金刚石薄膜方法

利用金刚石纳米粉引晶法和常规研磨方法分别在单晶硅衬底上制备金刚石薄膜,并采用扫描电镜、激光拉曼方法对所制备样品进行表征,通过SEM和拉曼谱分析,与研磨法生长金刚石薄膜相比,利用金刚石纳米粉引晶方法可以大大提高金刚石薄膜的成核速度,生长速率达到2μm/h以上。对相同碳源浓度下生长的金刚石薄膜样品的SEM和拉曼谱分析,采用引晶法生长的金刚石薄膜质量明显高于研磨法。     

某厂常压热水锅炉房的改造

本文分析了常压热水锅炉的优劣,并对某厂的热水锅炉房进行改造。主要通过调整膨胀水箱的位置和重新对热水循环泵选型两方面,将有压锅炉房改造为常压锅炉房。     

云南卫星林火监测中的地面核查辅助决策模型研究

基于卫星林火监测发现的地面高温热源坐标,研究了供基层单位开展地面核查、处置的辅助决策模型。首先利用空间查询分析,获取热点所在林区、县市、乡镇以及最近地名参考信息,然后,建立预警模型,将热点危险性进行分级,并给出了与之对应的地面核查处置应对方法。该模型能支持基层单位快速、经济地处置林火热点。     

Effect of microstructures restoration on high temperature fatigue behavior of DZ125 superalloy

Combination of hot isostatic pressing(HIP) and rejuvenation heat treatment(RHT) technology was used to restore creep-damaged DZ125 directional solidified superalloy, and the influence of microstructure restoration on high temperature fatigue behavior of the samples was explored. The results show that the HIP+RHT process could effectively heal internal cavities and recover the degraded γ’ phase in creep-damaged DZ125 superalloy to cubic particles similar as in as-received sample. After restoratio...