Simulation of dynamic recrystallization for an Al-Zn-Mg-Cu alloy using cellular automaton

A cellular automata (CA) model has been developed to predict and control the microstructure evolution during hot deformation on 7085 aluminum alloy. The initial microstructure and thermal-mechanical parameters were used as the input data of the CA model. To link microstructure evolution with macroscopic flow stress, dislocation density was set as an important internal state variable. The hot deformation behavior of 7085 aluminum alloy was studied by isothermal compression tests under a deformation temperature range of 623–723 K and a strain rate range of 0.001-1s^?1 up to true strains of 0.53–1.20. Electron backscattered diffraction technique and the CA model were utilized to systematically investigate the effects of strain, strain rate and deformation temperature on the microstructure evolution, and further to predict the average grain diameter and the recrystallization fraction after deformation. The simulated results were validated by the experimental data to demonstrate the feasibility and predictability of the CA model.     

Accelerating leaching of copper ore with surfactant and the analysis of reaction kinetics

To solve the problem of low permeability and lower extraction rates of high-mud ores, a surfactant was added as a penetrant to the pregnant leaching solution during column leaching tests. On the basis of the theories of physical chemistry and seepage flow mechanics, the mechanism by which seepage is enhanced under the effects of the surfactant was analyzed. The results show that the action modes of the surfactant were divided into four aspects: changing the wettability of the ore, reducing the viscosity of the leaching solution, adsorbing onto the surface of ore, and enhancing the permeability effect. The findings of column leaching tests demonstrated that permeability was substantially improved by the surfactant. In the later period of leaching, the permeability coefficient was two times higher than that of the control group. Meanwhile, the ore extraction rate increased by approximately 10%. During the leaching process, the surface tension of the solution did not substantially change, and that of the solution with surfactant increased slightly. The kinetics analysis of ore column leaching illustrated that the leaching processes were controlled by both internal diffusion(principal factor) and chemical reaction.     

铝、硅添加对方镁石-铝镁尖晶石质免烧耐火材料性能的影响

采用电熔镁砂和电熔尖晶石为主要原料,以葡萄糖和水合硫酸铝为复合结合剂,以金属铝粉和单质硅为添加剂,制备方镁石-铝镁尖晶石质免烧耐火材料,研究了不同热处理温度下铝加入量及硅铝复合添加对耐火材料显微结构、烧结性能及力学性能的影响。结果表明,随着铝粉加入量的增加,方镁石-铝镁尖晶石免烧耐火材料经不同温度处理后的线膨胀率、常温抗折强度和常温耐压强度增加,并且高温抗折强度也不断提高;另外,金属铝和单质硅的添加会引起耐火材料在升温过程中的增重并减少材料的体积膨胀,从而进一步提高材料的常温力学性能。     

偏转板伺服阀前置级结构参数优化研究

通过改变偏转板伺服阀劈尖高度和V形槽下端喷口的导流长度等结构参数,建立新的偏转板前置级模型,利用ICEM和FLUENT软件对前置级流场进行静态特性分析;对前置级流量曲线进行二次拟合,建立伺服阀系统数学模型,利用SIMULINK仿真模型进行动态仿真,分析偏转板伺服阀系统的动态特性,从而优化偏转板伺服阀前置级结构参数。结果表明,适当降低偏转板伺服阀劈尖高度,保持劈尖宽度不变,可增大偏转板伺服阀前置级的流量增益和提升伺服阀的响应频率;增加V形槽喷口的导流长度,会减小偏转板伺服阀前置级流量增益和降低伺服阀的响应频率。     

不同药剂对无花果夏季水培扦插效果的影响

以"美丽亚"品种无花果一年生枝条为实验材料,研究夏季高温条件下不同浓度百菌清及萘乙酸(naphthylacetic acid,NAA)对水培扦插生根的影响。结果表明:与对照相比,除百菌清200 mg/L试验组外,各药剂组对无花果扦插生根及侧枝萌发具有明显促进作用,其中混合药剂处理组较单一药剂处理更能提高无花果水培扦插生根效率;从扦插生根时间、生根率、根长、根鲜重及侧枝数等指标结果表明,各处理组中百菌清200 mg/L+NAA 400 mg/L溶液对无花果水培扦插苗促根效果最佳。     

基于单片机的电子节气门PID控制系统

以Bosch公司DV-E5型节气门为控制对象,基于PID算法完成了控制系统的软硬件设计.系统采用AT89C51单片机作为主控单元,选用LMD18200芯片驱动节气门中的直流电机,同时以PCF8591作为AD转换芯片,采用LCD1602显示动态控制参数,并用C语言编写了系统控制软件,在Proteus上对主要软件模块进行了仿真,搭建了节气门PID控制实验平台,完成了对节气门开度位置控制的实验和测试,实验结果表明:系统阶跃响应时间约300ms,稳态误差小于1%,滞后和超调不明显.     

细菌群体趋药性算法在多元非线性回归分析中的应用

利用细菌群体趋药性优化算法的优化速度和精度超过其他一些常见群体优化算法的优势,对多元非线性回归问题进行分析,并将该方法应用到混凝土重力坝顺河向位移的预测中,分析结果表明拟合效果较好,为解决回归问题提供了一种新思路.     

基于无质量地基模型的重力坝地震响应分析

假设在大坝附近一定范围的地基是线弹性、无质量的、地震激励均匀作用在边界上,采取人工模拟合成地震波,建立无质量地基模型,对龙滩重力坝-地基系统进行了地震响应分析.计算结果表明坝体动力反应一般滞后于地震波,且滞后程度与坝体结构刚度有关,同时,坝体内大部分拉应力均大幅度减小,但坝踵部位的拉应力有所增加,坝上游折坡点附近还有一定的拉应力.与考虑了粘弹性人工边界模型相比,无质量地基模型的动力响应峰值增加了4%~59.8%.     

混凝土面板施工期温度及应力分析

温度变化可引起结构内力的变化,导致混凝土裂缝;对结构引起的应力重新分布,随着温变而变化.温度变化引起的应力甚至超过其它荷载应力,尤其是在结构温度急剧变化时,将产生很大的拉应力,而导致混凝土的开裂破坏.因此通过数值模拟计算对大坝面板混凝土进行抗裂分析,依据面板混凝土的浇筑进度计划用方程有限元格式,选择格式中权函数及解的稳定性进行温度应力数值计算,得到不同时段不同工况下面板混凝土的温度场与温度应力值,从而得到降低混凝土面板开裂风险的措施.     

界面二氧化硅层对二极管辅助硅基磁电阻效应影响的研究

本文制备了二极管辅助的晶体硅磁阻(magnetoresistance,MR)器件,研究了界面二氧化硅层的磁阻放大作用及器件在硅基磁电子器件中的可能应用.通过有与无二氧化硅层的实验对比,发现引入二氧化硅层后器件的磁阻在室温和1.2T磁场下达到了527%,磁阻性能提升了76%以上.通过对无磁场作用下伏安特性的测量,证明了氧化硅层的引入增加了界面电阻,通过等效电路分析,对相关机理进行了讨论.这项工作将为硅基磁电子器件的可能应用提供一种新的方法.