基于林位错强化的晶体塑性模型的稳定性缺陷及改进

基于林位错强化的晶体塑性有限元模型物理意义清晰简洁,具有广泛的应用。然而,只考虑林位错强化的模型忽略了共面位错之间的相互作用,导致模拟结果常常出现异常的扭曲失稳现象。针对以上问题,通过分析位错之间的相互作用,在林位错强化模型中引入自硬化作用对模型进行改进。对改进前后两个模型模拟单晶体沿单个和多个方向拉伸的变形模式以及冷轧铝板剪切带的形成特征进行了比较。结果显示,对于单晶单滑移,两个模型的稳定性表现一致;但是对于单晶多滑移,改进前的模型出现了扭曲失稳,而引入自硬化的改进模型对于多滑移系的模拟符合真实情况,并改善了模型的稳定性问题。对于冷轧铝板发生剪切变形时剪切带的形成特征,林位错强化模型的不稳定性放大了材料的失稳变形,模型的低稳定性和材料的变形失稳叠加,导致预测的结果失稳程度过高;而引入自硬化作用的改进模型改善了稳定性问题,可以真实地反映材料本身的失稳。

Side effects of budesonide in liver cirrhosis due to chronic autoimmune hepatitis: Influence of hepatic metabolism versus portosystemic shunts on a patient complicated with HCC

AIM:To investigate the systemic availability of budesonide in a patient with Child A cirrhosis due to autoimmune hepatitis (AIH) and primary hepatocellular carcinoma,who developed serious side effects. METHODS:Serum levels of budesonide,6β-OH-budesonide and 16α-OH-prednisolon were measured by HPLC/MS/MS; portosystemic shunt-index (SI) was determined by 99mTc nuclear imaging.All values were compared with a matched control patient without side effects. RESULTS:Serum levels of budesonide were 13-fold increased in the index patient.The ratio between serum levels of the metabolites 6β-OH-budesonide and 16α-OH- prednisolone,respectively,and serum levels of budesonide was diminished (1.0 vs.4.0 for 6β-OH-budesonide,4.2 vs. 10.7 for 16α-OH-prednisolone).Both patients had portosystemic SI (5.7 % and 3.1%) within the range of healthy subjects.CONCLUSION:Serum levels of budesonide Vary uP to 13-fold in AIH Patients with Child A eirrhosis in the absenee ofrelevant Portosystemic shunting.Redueed hePatiemetabolism,as indicated by redueed metabolite-to-drugratio,rather than Portosystemie shunting may explainsystemic side effects of this drug in cirrhosis